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          S C EC                                                           California
                    Inside this Issue...                                        Quarterly Newsletter
                      See Back Page
                                                                                           Fall 1995
                                                                                                       Volume 1, Number 3

                                                                          Preliminary Results from
                                                                          the Los Angeles Region
                                                                          Seismic Experiment

                                                                          Introduction: Why LARSE?
                                                                          R ecent damaging earthquakes in the Los Angeles region have
                                                                          highlighted earthquake hazards associated with thrust faulting.
                                                                          As a consequence of the “bend” in the San Andreas fault north of
                                                                          the Los Angeles region (see Figure 1, opposite), tectonic strain in
                                                                          southern California is partitioned in the earth’s upper crust
                                                                          among thrust faulting, chiefly in the Transverse Ranges, strike-slip
                                                                          faulting, chiefly in the region south of the Transverse Ranges, and
                                                                          folding in both regions. Coupling of upper-crustal deformation to
                                                                          lower-crustal and mantle deformation is still poorly understood,
                                                                          although some progress has been made using geodetic data and
                                                                          lithospheric imaging. There is an urgent need to understand how
                                                                          the accumulating strain is likely to be relieved spacially and
                                                                          temporally so that preparations can be better made by emergency
                                                                          planning agencies, city planners, and engineering design advisory
                                                                          agencies. This need requires a fundamental knowledge of the
                                                                          crustal structure in southern California–the subdivision of the crust
                                                                          into blocks, the properties of those blocks, and the coupling between
                                                                          the blocks–and also a knowledge of how stress is being applied to
                                                                          this structure.

                                                                          To address the need for knowledge of crustal structure, the U.S.
                                                                          Geological survey and the Southern California Earthquake Center
                                                                          have initiated a program of seismic imaging known as the Los
                                                                          Angeles Region Seismic Experiment (LARSE). Preliminary
Figure 1. Fault map of Los Angeles region (from Jennings, 1975) showing   images from the LARSE have illuminated a number of the
locations of sources and receivers for October 1994 LARSE airgun and
explosion surveys. CBF, Catalina basin fault; SPBF, San Pedro Basin
Fault; PVHF, Palos Verdes Hills Fault; NIF, Newport-Inglewood Fault;
SMF, Sierra Madre Fault Zone.                                                                                         See "LARSE" on Page 4
 SC EC      Southern California Earthquake Center                                                                                 Page 2

From the Center Directors...                                           Keiiti Aki                          Thomas Henyey
                                                                       Science Director                    Executive Director

The Case for a National
Earthquake Hazards
Reduction Program

The population in the             understanding of the               in cities such as Tokyo,           has been learned from the
world’s “earthquake belts”        earthquake hazard. Even            Taipei, San Francisco, Los         laborious work of several
is increasing at a rapid rate.    moment frame steel and             Angeles, Salt Lake City,           generations of scientists and
This is because the same          wood frame structures, once        Seattle, Vancouver, Naples,        engineers who were fasci-
geologic processes respon-        believed by engineers to be        and Nice we rely on a              nated by the awesome
sible for earthquakes also        virtually invincible to the        complex and delicate               power of earthquakes, and
produce some of the               strongest earthquake               infrastructure that is highly      were intrigued by the
world’s most desirable and        shaking, are turning up            vulnerable to strong earth-        possibility of forecasting
valuable real estate. But         with serious problems,             quakes. So just as we              both their occurrences and
often with few resources at       resulting from both design         continue to fight the major        their effects, in order to
their disposal, large seg-        flaws and poor quality of          diseases of our time, we           warn populations and
ments of these populations        construction. In cities of         must continue to wage war          harden them against
are erecting structures too       second and third world             on the risks from earth-           potential destruction. For
feeble to withstand even          countries such as Mexico           quakes and other natural           the past 25+ years, the
modest shaking. In the            City, Istanbul, Cairo,             hazards.                           National Earthquake
United States, many such          Mindanao, Jakarta, and                                                Hazards Reduction Pro-
structures remain from            Athens, the population at          Almost everything we now
earlier times or are continu-     risk mounts sharply and            know about earthquakes
ing to be built without a full    irrevocably each year, while       and how to deal with them                  See "NEHRP" on Page 3

What Is the Southern California Earthquake Center?

The Southern California Earthquake Center (SCEC) actively            • Defining, through research, when and where future damaging
coordinates research on Los Angeles region earthquake hazards          earthquakes will occur in southern California;
and focuses on applying earth sciences to earthquake hazard          • Calculating the expected ground motions; and,
reduction. Founded in 1991, SCEC is a National Science Founda-       • Communicating this information to the public.
tion (NSF) Science and Technology Center with administrative
and program offices located at the University of Southern            To date, SCEC scientists have focused on the region’s earthquake
California. It is co-funded by the United States Geological Survey   potential. Representing several disciplines in the earth sciences,
(USGS). The Education and Knowledge Transfer programs are            these scientists are conducting separate but related research
co-funded by the Federal Emergency Management Agency                 projects with results that can be pieced together to provide some
(FEMA). The Center’s primary objective is to develop a “Master       answers to questions such as where the active faults are, how often
Model” of earthquakes in southern California by integrating          they slip, and what size earthquakes they can be expected to
various earth science data through probabilistic seismic hazard      produce. Future work will consider seismic wave path effects
analysis. The SCEC promotes earthquake hazard reduction by:          and local site conditions for developing a complete seismic
                                                                     hazard assessment of southern California.
                                                                                                                                 Page 3

NEHRP continued from Page 2 ...
gram (NEHRP) has been the          and maximum rupture              1992 and Northridge 1994        consider bold new ap-
foundation of this country’s       lengths–both critical param-     are graphical reminders that    proaches. The Southern
research efforts.                  eters for seismic hazard         the San Andreas is not the      California Earthquake
                                   assessment.                      only game in town.              Center embodies one new
The most important record                                                                           approach, where knowledge
we have is that of past            The theory of plate tecton-      New technologies devel-         accumulated in fundamen-
earthquakes, culled from a         ics, now only thirty years       oped over the last decade       tal research areas is inte-
global seismic network             old, has revolutionized          now permit us to look at the    grated and distilled so that
initiated about the begin-         earth science, and for the       earth in new ways. Broad-       it can be transmitted to the
ning of this century. The          first time explains the origin   band seismometers provide       general populous in a form
magnitude-frequency                of earthquake stresses. But      a detailed look at the          useful for earthquake
                                                                    earthquake source; the          hazard mitigation. This
      "...just as we continue to fight the                          Global Positioning Satellite    requires a conscious effort
     major diseases of our time, we must                            (GPS) system measures           to promote communication
      continue to wage war on the risks                             strain accumulating over        among researchers and
                                                                    wide regions of the earth’s     between the producers and
              from earthquakes..."                                  crust and relates it to         consumers of earthquake
                                                                    earthquake potential; and       knowledge. It means
distribution of earthquakes,       we are still far from under-     portable digital seismic        sharing, rather than guard-
first extracted from the           standing the magnitude and       instruments allow detailed      ing, what each one knows.
global data in the 1940s, is       distribution of stresses in      studies of fault zones and
now one of the cornerstones        the crust, and the relation-     the geologic factors control-   And finally, while we must
of worldwide seismic               ship between stress and          ling strong ground motions      not shrink from reporting
hazard estimation. How-            earthquake potential.            from large earthquakes.         the natural diversity of
ever, statistics on the largest,   Recent studies relating          Networks of all of these        opinion and uncertainty
most damaging earthquakes          static stress changes in past    instruments are greatly         (which promotes further
are inadequate in most             earthquakes to future            enhancing our observa-          and deeper scientific study)
seismically active regions in      earthquake potential may         tional resolution, and          in our science, we must
the world. A basic, still          be the first step in this        shortening the time it takes    strive to reach some com-
unanswered question is             direction.                       to understand what hap-         mon ground as to the nature
whether such events in a                                            pens during an earthquake.      of the earthquake problem
given region tend to cluster       The concepts of seismic
in time or are largely quasi-      moment (which links earth-              "...we must strive to reach some
periodic.                          quake rates to plate tectonic         common ground as to the nature of
                                   rates) and the characteristic
Fundamental data on the            earthquake (which relates the
                                                                               the earthquake problem..."
geometry and slip rates of         size of future earthquakes to
faults have come largely           the rupture lengths of past      So while much has been          at any given time. We must
from geologic investiga-           earthquakes) have found          learned over the last three     work toward consensus
tions–mostly carried out in        widespread use in seismic        to four decades, many           building, or perhaps more
the last two decades. These        hazard analysis. Yet we still    questions remain and much       appropriately, “capturing
data are crucial for extend-       have a rather primitive          is left to be done. The         the composite state of
ing the historic seismic           understanding of how             potential for fundamental       knowledge of an informed
record back in time to             seismic moment is distrib-       breakthroughs in earth-         scientific community.”*
improve the statistics on          uted among the many faults       quake hazard assessment         Doing so will benefit both
large earthquakes as well as       occurring along an active        exist perhaps more now          society and the relevance of
for documenting which              plate boundary, and the          than ever before. That is       our science.
faults are most active. This       notion of characteristic         why a strong and viable
work is exceedingly time           earthquake seems to be           NEHRP is essential and
consuming per data point,          losing ground to more            why we must press forward       *C. Allin Cornell, Professor, Dept.
                                                                                                    of Civil Engineering, Stanford
and as such we have only           complex models of fault          with the basic scientific
                                                                                                    University; SCEC Master Model.
scratched the surface in our       rupture. Recent earth-           study of earthquakes. But
understanding of slip rates        quakes such as Landers           at the same time, we must                                        ♦
 SC EC       Southern California Earthquake Center                                                                                 Page 4

LARSE continued from Page 1 ...

structural features originally       deployed along Line 1 with a       correspondence with numer-        fired along multiple traverses
targeted, including offshore         minimum spacing through the        ous individuals and private       of the offshore segments of the
faults, basement rocks beneath       San Gabriel Mountains of 1         groups. The public reception      three lines. The airguns were
the Los Angeles basin, and           kilometer. During four weeks       of this high-profile experiment   recorded by a 4-kilometer
deep crustal structure beneath       of continuous monitoring, over     was generally positive, owing     streamer, 10 ocean-bottom
the San Gabriel Mountains.           160 teleseisms and over 400        in large part to the recent       seismographs, and 170 land
Given the general high quality       local events were recorded.        occurrences of the Northridge     seismographs. In the second
of the data, more refined                                               and other earthquakes in the      phase of LARSE94 (Figure 1),
analysis will likely resolve         In 1994, LARSE continued with      area.                             explosions were detonated
upper-crustal structures and         airgun and explosion experi-                                         along the onshore segment of
additional deeper structures, so     ments along three lines,           Seismograph deployment            Line 1 and were recorded by a
that we can begin to define the      including Line 1, crossing the     required access along numer-      stationary array of 640 seismo-
various crustal blocks that          Los Angeles region and the         ous fenced drainage canals and    graphs assembled from
make up the tectonic frame-          offshore Continental Border-       through other publicly owned      numerous institutions in North
work of the Los Angeles              land (LARSE94; Figure 1).          and privately owned facilities.   America. Through the

  Figure 2. Constant-offset
  reflection section along the
  offshore part of Line 1 (Brocher
  et al., 1995). Ocean-bottom
  seismograph locations shown by
  black dots. Note differing
  sediment deformation between
  San Pedro and Catalina basins.

Experiment Design
                                     Onshore parts of Lines 2 and 3     Security for the seismographs     northern Los Angeles basin
and Data                             are, respectively, Santa Monica    required, in many cases,          and San Gabriel Mountains,
Acquisition                          northward through                  complete burial of the recorder   shots were spaced 1000 meters
                                     Northridge, and Redondo            and batteries. Noise suppres-     apart and the seismographs
LARSE began in 1993                  Beach eastward through the         sion required up to six passes    100 meters apart in order to
(LARSE93) with a passive             Los Angeles basin. Existing        along the offshore segments of    produce both a reflection and
experiment along a line              oil-industry seismic-reflection    the three lines with the airgun   refraction image of the crust.
extending northeastward from         and well-log data will be used     sources with a plan eventually    North and south of this
Seal Beach across the Los            to determine the structure of      to “stack” the data. It also      densely instrumented segment,
Angeles basin and San Gabriel        the sedimentary basins along       required extensive pre-           seismographs and shots were
Mountains (Figure 1, Line 1).        these three lines.                 experiment noise measure-         spaced more widely to produce
The objective of this experi-                                           ments, avoidance of freeways,     a wide-angle reflection and
ment was to collect seismic-         LARSE94 required unusual           and detonation of explosions      refraction image chiefly of the
waveform data from local and         emphasis on several aspects of     between the hours of 1:30 and     middle and lower parts of the
teleseismic earthquakes to           seismic data acquisition in the    4:30 am. Care was taken to        crust.
refine three-dimensional             urban environment. The             avoid damage from the
images of the lower crust and        permitting process, which took     explosions–both perceived and     The chief targets along offshore
upper mantle in southern             two years, required not only an    real.                             Line 1 were the Catalina, San
California, especially in the San    environmental assessment but                                         Pedro basin, and Palos Verde
Gabriel Mountains and across         addresses to city councils and     During the first phase of         Hills faults (Figure 1). The
the San Andreas fault. During        other governmental bodies,         LARSE94 (Figure 1), 20 air-
LARSE93, approximately 88            extensive radio, television, and   guns, towed by Lamont
portable seismographs were           newspaper interviews, and          Doherty’s R/V Ewing, were
                                                                                                                  See "LARSE" on Page 5
                                                                                                                                  Page 5

LARSE continued from Page 4 ...

chief targets along onshore        which the faults might be          fine structural detail in         about 95%, and SNRs were
Line 1 were the top of base-       evident as discontinuities or as   constant-offset seismic-          generally excellent (Figures 3a,
ment beneath the Los Angeles       tabular low-velocity zones.        reflection sections (Figure 2).   below; Figure 4, page 6).
basin (never before imaged),       Sources and receivers were too     At onshore bedrock recording
the Elysian Park blind thrust      sparse to obtain clear images of   sites, airgun signals had good
fault system, believed to be the   the Newport-Inglewood fault,       to moderate SNRs (≥ 1, Figure     Preliminary Crustal
origin of the 1987 Whittier        origin of the 1933 Long Beach      3b), and at onshore sedimen-      Images
Narrows earthquake (M 5.9),        earthquake, or of the proposed     tary recording sites in the Los
the Sierra Madre fault system,     Compton-Los Alamitos blind         Angeles basin, moderate to        Preliminary seismic images
believed to be the origin of the   thrust fault in the southwestern   poor SNRs (≤ 1). The airgun       from Line 1 of LARSE94 are
1991 Sierra Madre earthquake       Los Angeles basin.                 signals carried over 200 km,      presented from south to north
(M 5.8), and the San Andreas                                          into the Mojave Desert. Ocean-    in Figures 2-4. A constant-
fault. LARSE94 was designed        Data quality obtained during       bottom seismogram return was      offset reflection section along
to image these features using      LARSE94 was generally good.        approximately 80%, and SNRs       the offshore part of Line 1
vertical-incidence and wide-       Airgun signals recorded by the     were commonly good to 70-         (Figure 2) (consisting of data
angle reflections and also         streamer have excellent signal/    kilometer offset. Data return
detailed velocity models, in       noise ratios (SNRs) and show       for the land explosions was               See "LARSE" on Page 6

Figure 3a (above right).
Record section for explosion
at Shotpoint 9450 (Figure 1),
at Seal Beach, reduced at 6
km/s. Clear signals recorded
through metropolitan Los
Angeles (ranges of 0-45 km)
show strong reflection
interpreted to be from
basement beneath
sedimentary and volcanic
deposits of Los Angeles
basin. Inset shows a 1-
dimensional velocity model
derived from this shot gather,
indicating 8-km depth to
basement. Also seen in
record section are strong
wide-angle reflections from
the lower crust (PiP) and/or
mantle (PmP) and mantle
refractions (Pn).

Figure 3b (below right).
Record section ("common-
receiver gather") for airgun
bursts along Line 1, recorded
at a seismograph near
Shotpoint 8260 (Figure 1),
near the crest of the San
Gabriel Mountains, reduced
at 6 km/s. Strong PiP/PmP
is seen. First arrival between
about 120 and 160 km with
the high apparent velocity is
interpreted as Pn.
 SC EC       Southern California Earthquake Center                                                                                   Page 6

LARSE continued from Page 5 ...

recorded on the tenth channel       (1.8-6.2 km/s) sedimentary and     recorded near the crest of the       Data are currently being
of the streamer) shows folded,      volcanic fill in the Los Angeles   San Gabriel Mountains indicate       processed for release as U.S.
faulted, and erosionally            basin. Based on the strength of    a prominent, subhorizontal           Geological Survey Open-File
truncated sedimentary rocks in      the basement reflection and the    reflective zone as shallow as 7.5    Reports. Most should be
San Pedro basin, but undis-         apparent velocity of the           s (about 22 kilometers depth)        released before the end of the
turbed sedimentary rocks to         refraction associated with it,     (Figure 4). This reflective zone     year.
the south in the Catalina basin.    basement rocks may have a          can be traced in preliminary
Some of the multiple reflec-        high seismic velocity (6.5-72.     stacked data throughout the                            Gary S. Fuis
tions apparent in this section      km/s), corresponding to            San Gabriel Mountains,                           Thomas M. Brocher
will be suppressed when the         gabbro or mafic metamorphic        forming a gentle arch, with                             James Mori
multichannel data are sorted.       rocks. Similar one-dimensional     weaker reflectivity above it at                  Rufus D. Catchings
                                    models are obtained from           the north and south margins of                      Uri S. ten Brink
A record section from an            reversing shots 30 kilometers      the San Gabriel Mountains and                       Kim D. Klitgord
explosion at Seal Beach (Figure     northeast of Seal Beach, near      also weaker reflectivity                        Robert G. Bohannon
3a) shows excellent SNRs            the Whittier fault (see Figure     beneath it (to 12 s) in the north-            US Geological Survey
through much of metropolitan        1).                                central San Gabriel Mountains.
Los Angeles. Arrivals are                                              The Moho is inferred from                            David A. Okaya
delayed through the Los             A reversing record section of      independent earthquake                             Thomas L. Henyey
Angeles basin (ranges of 0-45       air-gun signals recorded near      tomographic data to be at a                             USC/SCEC
kilometers) and advanced in         the crest of the San Gabriel       depth of about 30 kilometers
the San Gabriel Mountains           Mountains (Figure 3b) shows        (or about 10 s) beneath the San                    Robert W. Clayton
(ranges of 45-85 kilometers).       strong reflections from the        Gabriel Mountains. Wide-                                    Caltech
Importantly, a strong arrival at    lower crust and/or mantle          angle reflections from the 7.5 s
about 3.25 s reduced traveltime     (PiP/PmP) and also refracted       reflective zone and/or Moho                          Paul M. Davis
is interpreted as a reflection      arrivals from the mantle. This     are interpreted in Figure 3a.                       Mark L. Benthien
from the top of basement rocks      remarkable record owes its         This reflective zone, inter-                                  UCLA
beneath the sedimentary and         clarity to the quiet bedrock       preted to lie chiefly or entirely
volcanic rocks of the Los           recording location and to the      in the lower crust, may or may                        Trond Rybert
Angeles basin. Also evident in      fact that the airgun bursts were   not represent a decollement;                GeoForschungsZentrum
the section are reflections from    numerous (~one every 50            however, it almost certainly
the lower crust (PiP) and           meters) and produced a             represents an important change         Note: This article was
mantle (PmP) and refracted          coherent signal distinguishable    of physical properties, or a           submitted for publishing to
arrivals from the mantle (Pn).      through the noise.                 “block” boundary, within the           AGU/Eos in September 1995.
A one-dimensional velocity          Explosion record sections                                                       See "LARSE" on Page 7
model for the shallow structure
near the Seal Beach shotpoint
(Figure 3a inset) indicates
approximately 8 kilometers of
low- to intermediate-velocity

   Figure 4 (right). Record
   sections for explosions at
   Shotpoints 8220 and 8260
   (Figure 1), near crest of San
   Gabriel Montains.          No
   reducing velocity; corrected
   only for spherical divergence.
   Strong reflector at 7.5 s is
   interpreted as lower-curstal
   feature (about 22 km deep).
   Reflector can be traced as
   gentle arch throughout San
   Gabriel Mountains.
                                                                                                                                       Page 7

LARSE continued from Page 6 ...

        REFERENCES, LARSE Results

        Brocher, T.M., R.W. Clayton, K.D. Klitgord, R.G.              Jennings, C.W., compiler, Fault Map of California, Califor-
        Bohannon, R. Sliter, J.K. McRaney, J.V. Gardner, and J.B.     nia Division of Mines and Geology, Sacramento, Califor-
        Keene, Multichannel seismic-reflection profiling on the       nia Geologic data Map No. 1, scale 1:750,000, 1975.
        R/V Maurice Ewing during the Los Angeles Region
        Seismic Experiment (LARSE), California, U.S. Geological       Kohler, W.M., and G.S. Fuis, Empirical dependence of
        Survey Open-File Report 95-228, 70 p., 3 pl., 1995.           seismic ground velocity on the weight of explosive,
                                                                      shotpoint site condition, and recording distance for
        Hauksson, E., The 1991 Sierra Madre earthquake                seismic-refraction data, Bulletin of the Seismological Society
        sequence in Southern California: seismological and            of America, 82, 2032-2044, 1992.
        tectonic analysis, Bulletin of the Seismological Society of
        America, 84, 1058-1074, 1994.                                 Shaw, J.H., and J. Suppe, Earthquake hazards of active
                                                                      blind-thrust faults under the central Los Angeles basin,
        Hauksson E., L.M. Jones, T.L. Davis, L.K. Hutton, A.G.        California, Journal of Geophysical Research (in press, 1995).
        Brady, P.A. Reasenberg, A.J. Michael, R.F. Yerkes, P.
        Williams, G. Reagor, C.W. Stover, A.L. Bent, A.K. Shakal,     Weldon, R.J., and E.D. Humphreys, A kinematic model
        E. Etheredge, R.L. Porcella, C.G. Bufe, M.J.S. Johnston,      of southern California, Tectonics, 5, 33-48, 1986.
        and E. Cranswick, The 1987 Whittier Narrows earth-
        quake in the Los Angeles metropolitan area, California,       Wright, T.L., Structural geology and tectonic evolution of
        Science, 239, 1409-1412, 1988.                                the Los Angeles basin, California, in Active Margin Basins,
                                                                      edited by K.T. Biddle, American Association of Petro-
        Hearn, T.M., and R.W. Clayton, Lateral velocity varia-        leum Geologists Memoir 52, 35-134, 1991.
        tions in southern California: 2 Results for the lower crust
        from Pn-waves, Bulletin of the Seismological Society of       Ziony, J.I., and R.F. Yerkes, Evaluating earthquake and
        America, 76, 511-520, 1986.                                   surface-faulting potential, in Evaluating Earthquake
                                                                      Hazards in the Los Angeles Region--An Earth-Science
        Humphreys, E.D., and Clayton, R.W., Tomographic               Perspective, edited by J.I. Ziony, U.S. Geological Survey
        image of the southern California mantle, Journal of           Professional Paper 1360, 43-91, 1985.
        Geophysical Research, 95, 19, 725-19, 746, 1990.

Acknowledgments. We are             Prodehl of the University of      Brian Laird of the USGS and          Borax Co., and numerous
indebted to the following           Karlsruhe, Germany; Elizabeth     Michele Robertson, Joyjeet           private citizens of the Los
persons and institutions for        Ambos of the California State     Bhowmik, and Katrin Hafner           Angeles region for permission
supplying seismographs and/         University at Long Beach; and     of SCEC supervised surveying         to operate on lands under their
or field hands: James Fowler,       John Louie of the University of   and deployment of seismo-            jurisdiction or ownership. The
Marcos Alvarez, Steven              Nevada at Reno. Lamont-           graphs, and assisted with data       National Earthquake Hazards
Michnik, and William                Doherty Earth Observatory         reduction and figures. We            Reduction Program and the
Koperwhats of IRIS/PASSCAL;         operated the R.V. Ewing; James    thank the U.S. Forest Service,       National Science Foundation
Isa Asudeh and Tim                  Gardner, Ray Sliter and Jock      U.S. Bureau of Land Manage-          funded this experiment. We
Cartwright of the Geological        Keene of the USGS and John        ment, U.S. Army Corps of             thank David Hill, Thomas
Survey of Canada; Roger             McRaney of SCEC assisted          Engineers, U.S. Naval Weapons        Holzer, and Walter Mooney for
Borcherdt of the USGS; Kate         with airgun data acquisition.     Station Seal Beach, Caltrans,        reviews of this paper.
Miller of the University of         Edward Criley and Thomas          Metropolitan Water District of
Texas at El Paso; Michael           Burdette of the USGS super-       Southern California, County of                       Gary S. Fuis, et al.
Fehler of the Los Alamos            vised permitting, loading, and    Los Angeles, CalMat, Rose
National Laboratory; Claus          shooting; Janice Murphy, and      Hills Cemetery, Chevron, U.S.                                       ♦
 SC EC      Southern California Earthquake Center                                                                                        Page 8

Quarter Fault                                                Each Issue of the SCEC Newsletter will feature a southern
                                                             California fault. In this issue, we feature...

The Palos Verdes Fault

       The Palos Verdes
       Fault angles
       northwest under
       the Vincent
       Thomas Bridge
       toward the giant
       dinosaur cranes.

M      uch of nature is fractal. Capillaries, arteries and veins        lent, is exposed at the little bend in the Palos Verdes Fault.
branch out in a similar fashion at different scales. Stream tributar-
ies are often smaller versions of the river they’re feeding. Frac-      And what a pretty sight all that uplifted schist and sediment is:
tures and faults in a region will also sometimes repeat their           with its houses and gardens spilling down ancient wave cut
geometries. The Palos Verdes Fault, for example, is a scaled down       terraces, the Palos Verdes peninsula rises out of our L.A. mega-
version of the mother of all of southern California’s faults: the San   lopolis still looking like the channel island it was only few
Andreas. Where the dextral San Andreas fault is moving roughly          hundred thousand years ago. Often misty and mysterious, with
30 mm per year in Southern California., the dextral Palos Verdes        peacocks wailing and the nightly patter of furry four footed beasts
fault runs at roughly 3 mm per year. Where the San Andreas is           scampering across rooftops and down gullies, Palos Verdes
1000 km long, the Palos Verdes fault is approximately 100 km            doesn’t so much call to mind San Francisco, with which it is
long. The San Andreas has a “big bend” where the Transverse             sometimes compared, but a story-book Hobbit-land.
Ranges are being squeezed up. The Palos Verdes fault has a “little
bend” where the peninsula is being squeezed up by 0.04 mm/yr.           It is currently thought an earthquake as large as a ML 7.2 could
The “Pelona Schist” is exposed at outcrops along the big bend in        occur if the entire trace of the P.V. fault ruptured, which could
the San Andreas. The Catalina Schist, its southwestern equiva-          prove to be most unfortunate as it runs through L.A. harbor,

                                                                                                                    See "PV Fault" on Page 9
                                                                                                                                     Page 9

   Insurance Industry Workshop                                              FEMA's First Biennial National
   Proceedings and Audio Tapes                                            Mitigation Conference: "Partnerships
   Available                                                               for Building Safer Communities"
                                                                                   December 6-8, 1995
   In our next issue, we will review the November 9-
   10 SCEC Insurance Industry Workshop results.                          Topics discussed will include risk assessment,
   Printed proceedings will be available free of                         measuring mitigation success, building codes and
   charge to participants of the workshop, and can be                    enforcement, the latest research, GIS/GPS, pre- and
   obtained by others (release date and cost to be                       post-disaster mitigation, floods, wind/hurricanes,
   determined) through SCEC.                                             earthquake hazards, all hazards insurance, public
                                                                         awareness and involvement, retrofitting, legislative
   Audio tapes are available immediately. To order,                      updates, and more.
   contact SCEC's Knowledge Transfer office (see
   below).                                                               Who should attend this conference? Anyone who
                                                                         has a stake in mitigation, community development,
   All tapes are fully guaranteed for exchange or                        or disaster planning and recovery, and understands
   refund. 1-Tape Sets (one tape per Workshop                            the need to strengthen existing relationships and
   Session) are $4. Tapes may be ordered separately,                     develop new partnerships to reduce our Nation's
   or complete sets (12 tapes) may be ordered for $45                    hazard vulverability.
   total. Shipping charges are not included.
                                                                         For more information: Call the Federal Emergency
   Contact:                                                              Management Agency at (800) 769-3861.

   SCEC Knowledge Transfer
   University of Southern California
   Mail Code 0742                                                        Earthquake Map Now Available from
   Los Angeles, CA 90089-0742                                            the U.S. Geological Survey
   phone 213/740-1560
   e-mail:                                              “Earthquakes in California and Nevada” depicts the
                                                                         epicenters of 300,000 earthquakes, including 49 of
                                                                         magnitude 6.5 or larger that have occurred in the
                                                                         two-state area since 1836.

                                                                         The map offers a ready reference for areas that have had
PV Fault continued from Page 8 ...                                       few if any earthquakes during the past 160 years.
                                                                         California’s great central valley, for instance, has only a few
under an oil refinery and other heavily developed areas. Recent          dots depicting earthquake epicenters.
seismic reflection experiments suggest the onshore fault splays
out into strands in a band as wide as 1.5 km near Gaffey Street          The map, priced at $12 for a paper copy or $22 for a
with most recent activity occurring in the northeastern strands.         laminated copy, including shipping costs, is available by
                                                                         mail only from:
Probably the most stimulating area to travel cross the fault—the
trace of which has been almost completely obscured by develop-                             Earthquake Maps
ment—is where it angles northwest directly between the two                               U.S. Geological Survey
support structures of the Vincent Thomas bridge. Its always                         Box 25046, Federal Center, MS 967
thought-provoking to consider the lay of the fault while driving                           Denver, CO 80225
over the crest of the bridge and gazing at L.A. harbor, its cargo,
cranes, oil tankers, coal mountains, the oil refineries and their        Orders must include the name and number of the map
flame capped exclamation points and beyond. It’s a long way              “Earthquakes in California and Nevada; Open-File Report
down.                                                                    94-647”, and a check or money order, payable to DOI/
                                                    Michael R. Forrest
SC EC    Southern California Earthquake Center                                                                                         Page 10

SCEC Annual Meeting: Glimpses
  The 1995 SCEC Annual Meeting was held at the Ojai Valley Inn in       Three invited talks were given before the working group meetings.
  Ojai, California, September 17 -19, 1995. Welcome remarks from        Jim Rice and Yehuda Ben-Zion presented "Rupture Dynamics, Slip
  SCEC Executive Director Tom Henyey were followed by statements        Patterns and Event Populations in Earthquake Fault Models;" Lynn
  from Jim Whitcomb (NSF) and John Sims (USGS). Participants            Sykes and Jishu Deng presented "Evolution of the Stress Field in
  heard special presentations on the progress of the Phase III Report   Southern California During the Past 200 Years and Implications for
  (Norm Abrahamson); Status of the GPS Initiative (Duncan Agnew);       Long-Term Earthquake Prediction;" and Ruth Harris, Ross Stein, and
  Results of LARSE (Rob Clayton); New Seismic Network Initiative        Robert Simpson presented "Earthquake Stress Triggering and
  (Egill Hauksson); Status of Northridge Investigations (Jim Mori);     Relaxation Shadows - An Explanation for the Pattern of Southern
  and the SCEC Research Utilization Council (Jill Andrews).             California Earthquakes from 1858-1995."

  Summary Reports from Group Leaders were presented by Kei Aki,         Future newsletters will cover more news from the meeting, and in
  Steve Day, Kerry Sieh, Rob Clayton, Duncan Agnew, Egill               the meantime, we picked out a few of our favorite moments to share
  Hauksson, and Leon Knopoff.                                           them with our readers here.
                                                                                                                             Jill Andrews
Page 11
 SC EC       Southern California Earthquake Center                                                                             Page 12

Feature: visit with a SCEC scientist

A Visit with Rachel Abercrombie

I ntoxicating and wonderful
as life is, it’s often easy to
forget that roses have thorns—        Center: Rachel
that pain and unpleasantness          Abercrombie
are sometimes crouching round         poses for the
the next corner, ready to             camera in front
spring. Like the pain of having       of the USC
to say that sad and ugly word,
“Goodbye,” to favored friends,
colleagues and mentors.               Upper right:
                                      USC's Periklis
Two departures are particu-           Beltas and
larly unpleasant this fall. First,    David Adams
Professor Kei Aki will be             help seal the
                                      Cajon Pass
spending half of each year on         borehole.
La Reunion Island. And now,
regrettably, it’s time to say         Lower right: A
goodbye to Rachel                     hammer and a
Abercrombie, whose dry                pick and a
British wit, insight, and             dynamite stick-
                                      -off to work!
inspiring industry will be
missed by the many collabora-         Lower left:
tors, loyal cohorts and friends       Retrieving the
she’s accumulated during her          sonde from the
tenure as a SCEC researcher.          borehole.
(We’ll most miss the staccato
                                      Upper left:
“WOT?” she uttered, when
                                      Derek Manov,
presented with a thought or           carrying the
plot of dubious scientific            down-hole
merit.)                               instrument he
Abercrombie has been a SCEC           develop.
researcher since November of
1991, when she arrived from
England through the SCEC
Visitor’s Program. “One
intent of the visitor’s program
is to identify young scientists
from other countries that            Peter Leary was Abercrombie’s      seismometer with two instru-    Cajon pass region. Leary and
would not be considering             SCEC sponsor scientist at that     ments at 1.5 and 3 km depth.    Abercrombie calculated the
potential opportunities for          time and he, with Derek            The 3 km seismometer was the    intrinsic and scattering
earthquake research in               Manov, had installed the first     deepest seismometer in all of   attenuation in the upper crust,
Southern California,” says Tom       borehole seismometer in the        North America.                  and Abercrombie also found,
Henyey of the program. “A            Cajon Pass Scientific drill hole                                   “There is indeed some seismic-
good example the success of          in August 1991. This instru-       Rachel used the borehole        ity on the locked segment of
this program was the Center’s        ment recorded the mainshocks       seismicity data to determine    the San Andreas.”
ability to attract Abercrombie       and aftershocks of the 1992        that constant stress drop
to Southern California and her       Joshua Tree, Landers and Big       scaling holds from about ML 0
subsequent research on               Bear earthquake sequences. In      to ML 7 and that the
microearthquakes using               November of 1993,                  Gutenberg-Richter b-value is
borehole instruments.”               Abercrombie replaced the           constant above ML 0.5 in the     See "Abercrombie" on Page 13
                                                                                                                                Page 13

Abercrombie continued from Page 12 ...

Rachel worked with Jim Brune       shock.                            required less effort than          Much as Rachel has loved
at the University Nevada,                                            putting them in, the operation     living in pink, brown and
Reno, for four months in 1994,     Having collected enough           kept the oil crew from Tiger       lovely Los Angeles and
further studying earthquake        borehole data since 1991 to (in   Wireline and a group of USC        navigating morning traffic on
parameters and showing the         Rachel’s words) “keep scien-      geophysics graduate students       the 405 and 110 freeways, she’s
that Gutenberg-Richter relation    tists busy for years,” and with   sharp and alert. The two           now going to a permanent
holds down to about ML 0. “I       her September departure           cables carrying the seismom-       position with the Institute of
definitely enjoyed working         imminent, Abercrombie went        eters weighed 1500 pounds          Geological and Nuclear
with her,” says Brune about        to retrieve the seismometers      each and Periklis Beltas (USC)     Sciences in green and
Abercrombie. “On our               from the Cajon Pass borehole      was good enough to tell            unpopulous Wellington New
microearthquake paper she                                                                               Zealand. “I’m looking forward
was willing to spend hours                                                                              to working on some new
counting tiny microearth-                                                                               problems. For example, the
quakes, cheerfully! Some say                "One intent of the visitor’s program                        seismotectonics of the
that she gave the best seminar              is to identify young scientists from                        Hikurangi Margin, and deep
that they had ever heard. She                                                                           earthquake sources. Also, if
certainly doesn’t take anyone’s
                                            other countries that would not be                           there happens to be a borehole
word for anything important                 considering potential opportunities                         available...”
unless she understands it                   for earthquake research in Southern
clearly (even if they are world             California..."                                              Abercrombie will still be active
famous!).”                                                                                              in SCEC research, however. “I
                                                                                                        hope to keep close links with
Abercrombie also worked                                                                                 SCEC. I will continue working
closely with Jim Mori (USGS                                                                             with two graduate students at
Pasadena) during her stay.         one early Saturday last July.     everyone the tale of how he        USC who are working on
“The first time I saw Rachel       (See photos opposite page.)       had seen a ship cable snap on a    SCEC related projects. I’ve
was when she came to Caltech.                                        dock in Greece and literally cut   really enjoyed working in
She was jaywalking across          “When you’ve been out there       a man in half.                     California. The ground has
Wilson Avenue, right in front      every two weeks for three                                            hardly stopped moving since I
of a motorcycle cop,” recalls      years....actually, I’m HOPING     The stress was quickly dissi-      arrived! I’m very grateful to
Mori. “When she stopped to         it’s the last time I have to go   pated with a laugh fest,           SCEC for the opportunity. The
wave at the Pasadena police-       out there!” she joked. Vandals,   however, which was orches-         monthly meetings especially
man, I thought, ‘This person is    unfortunately, sometimes made     trated by Abercrombie’s            enabled me to meet and get to
not from around here.’ Clearly     Abercrombie's visits to           husband (computer virtuoso         know scientists from all over
she wasn’t from around here,       download borehole data and        Phil). He told the assembled       California and Nevada. I’ve
but since that time I’ve had the   change batteries less than        about some of her work at          had some excellent opportuni-
pleasure to work with her and      delightful. She lost one          UCLA with Paul Davis, where        ties for collaborative work,
learned that southern Califor-     REFTEK, four batteries, one       she has been involved with         especially with Jim Brune and
nia has gained from the energy     GPS unit, numerous padlocks,      designing and testing seis-        Jim Mori. I’ve also made many
and enthusiasm she has             a transformer, and drilling       mometers for future deploy-        friends with whom, thanks to
brought to the work at the         tubing. Cables were cut, and      ment on Mars. Phil and             e-mail, I can stay in touch."*
Cajon Pass and on earthquake       vandals even stole a fiberglass   company gleefully imagined
source parameters.” By closely     T-hut. “But nobody took the       what it might be like to be a
examining the emergent onset       sensors, they’re still down in    Martian, walking the canals, on                  Michael R. Forrest
of the Landers 1992 event on       the hole. No one’s stolen         a balmy Martian afternoon,
seismogram recordings,             them!” said Abercrombie.          only to find metal missile         *Rachel’s new e-mail address
Abercrombie and Mori                                                 airborne seismometers raining      is:
determined the quake was           Though pulling the titanium       out of the sky, and dropping
actually a compound event. A       “sondes” out of the two           “THUNK!” around your feet,
Mw 4.4 followed by a Mw 5.6        boreholes at Cajon Pass           kicking up clouds of red dust.
“detonated” the Mw 7.3 main
SC EC      Southern California Earthquake Center                                                                                                      Page 14

SCEC Scientists' Publications, Fall 1995
       The complete SCEC scientists' publications listing is updated and available on a continuous basis. Please
       contact the SCEC Administrative Office, 213/740-5843, to obtain updated listings. Selected publications
       may be available through the Center; however, to obtain authorized copies of preprints or reprints, please
       contact the authors directly. The Spring quarterly newsletter includes all publications; subsequent
       issues will include newly submitted papers only.

 216. Leary, P. C., “Quantifying    “The Gutenberg-Richter or                  “Summary of Findings: Workshop             aftershock zone) and Hopper
 Crustal Fracture Heterogeneity     Characteristic Earthquake                  on Preparing a Digital Fault and           Canyon Segments of the Western
 by Seismic Scattering,”            Distribution, “Which is it?” by S. G.      Fold Map and Database for                  Transverse Ranges Deformation
 Geophysical Journal Interna-       Wesnousky, Bulletin of the Seismo-         Southern California,” report               Belt," Bulletin of the Seismological
 tional, 122, pp. 125-142,          logical Society of America, submitted      prepared for the Southern                  Society of America, Northridge
 January, 1995.                     1995.                                      California Earthquake Center,              earthquake volume, in press, 1995.
                                                                               August 29, 1995.
 217. Leary, P. C., “The Cause      220. Olsen, Kim B., R. Archuleta,                                                     226. Hauksson, Egill, K. Hutton, H.
 of Frequency-Dependent             “3-D Simulation of Earthquakes on          223. Knopoff, L. (title forthcom-          Kanamori, L. Jones, "Preliminary
 Seismic Absorption in Crustal      the Los Angeles Fault System,”             ing).                                      Report on the 1995 Ridgecrest
 Rock,” Geophysical Journal         Bulletin of the Seismological Society of                                              Earthquake Sequence in Eastern
 International, 122, pp. 143-151,   America, submitted August 1995.            224. Anderson, John G., Y. Lee, Y.         California, Seismological Research
 January, 1995.                                                                Zeng, S. Day, “Control of Strong           Letters, submitted October 1995.
                                    221. Field, Edward H., S.E. Hough,         Motion by the Upper 30 Meters,
 218. Sieh, K., “The Repetition     “The Variability of PSV Response           Bulletin of the Seismological Society of   227. Field, Edward H., “Spectral
 of Large Earthquake-               Spectra Across a Dense Array               America, submitted August 1995.            Amplification in a Sediment-Filled
 Ruptures,” Proceedings of the      Deployed During the Northridge                                                        Valley Exhibiting Clear Basin-Edge
 National Academy of Sciences,      Aftershock Sequence,” Earthquake           225. Huftile, G. J., and Yeats, R. S.,     Induced Waves”, Bulletin of the
 submitted August 1995.             Spectra, submitted September 1995.         1996, "Deformation Rates Across            Seismological Society of America,
                                                                               the Placerita (Northridge Mw=6.7           submitted October 1995.           ♦
 219. Kagan, Y. Y., Comment on      222. McGill, Sally; Grant, Lisa B.,

 Putting Down Roots in Earthquake                                                 Seismic Hazards Report Now Available
 Country: Order While They Last!
 If you live in southern California, you can get your free                         Reprints of Seismic Hazards in Southern California:
 copy of the layman's version of the "Seismic Hazards in                           "Probable Earthquakes, 1994 - 2024," published in the April
 Southern California–Probable Earthquakes, 1994-2024" at                           edition of the Bulletin of the Seismological Society of America,
 your local library. Organizations (both profit and non-                           is available through the SCEC Administrative Offices.
 profit) can arrange for large quantities through the                              Copies, which include color figures and maps, are $5 each.
 Southern California Earthquake Center by calling the
 phone number below.                                                               Contact:
                                                                                   SCEC Knowledge Transfer
 The 32-page, full-color handbook, authored by seismolo-                           University of Southern California
 gist Lucile M. Jones of the U.S. Geological Survey, explains                      Mail Code 0742
 the risks southern Californians face from earthquakes–and                         University Park
 what can be done about it.                                                        Los Angeles, CA 90089-0742
                                                                                   phone 213/740-5843
 Call 213/740-1560 and order now while supplies                                    fax 213/740-0011
 last!                                                                             e-mail:
                                                                Page 15

SCEC Research Activities

Research on the Hollywood Fault
Most Recent Surface Rupture on the "Ozzie and Harriet" Trench

James Dolan (University of
Southern California), Thomas
Rockwell (San Diego State
University), and Donovan
Stevens (California Institute of
Technology) drilled a North-       Right: Donovan
South transect of nine adjacent    Stevens, free as Peter
boreholes just west of down-       Pan, after he is raised
                                   out of the trench.
town Hollywood during the
late summer, 1995. Immediate
results showed that the most
recent surface rupture on the
Hollywood fault occurred
during latest Pleistocene to       Below: Tri-Valley
early or mid-Holocene time.        Drilling excavating a
                                   trench across the
Details of the borehole data are   Hollywood Fault,
available from principal author    directly in front of the
James Dolan.                       "Ozzie and Harriet"
Preliminary Conclusions

The present long quiescent
interval (between ~5,000 and
15,000 years), implies that the
Hollywood fault ruptures
during very infrequent, and
therefore possibly very large,
earthquakes. The authors
speculate that the Hollywood
fault may rupture either with
other faults in the 215 kilome-
ter-long Raymond-Hollywood-
Santa Monica-Malibu Coast-
Santa Cruz Island-Santa Rosa
Island fault system and/or
with the Santa Monica Moun-
tains blind thrust fault or
shallower blind thrust faults to
the south. Alternatively, very
infrequent Hollywood fault
earthquakes may reflect slip
rates of <<1 millimeter per

  See "Hollywood" on Page 16
 SC EC      Southern California Earthquake Center                                                                                   Page 16

Hollywood continued from Page 15 ...
Soil stability and logistical       boreholes were placed adjacent     was much slower and more          much greater than the 5 to 6
problems dictated the use of        to one another by drilling and     expensive than conventional       meters depth of exposure
the borehole technique, as a        logging one hole, backfilling      trenching, it allowed them to     provided by conventional
conventional trench, such as        with concrete, and drilling the    collect the data in safety at a   trenches. This method proved
the trench highlighted on the       adjacent hole after the concrete   site that would not support a     to be critical at this site, which
cover of the summer 1995 issue      had hardened. Using this           conventional trench. In           lies on an alluvial fan where
of the SCEC Quarterly newslet-      method, they achieved              addition, the adjacent-borehole   rapid sediment accumulation
ter, began to collapse as soon as   complete exposure of the fault     technique provided exposures      has deeply buried evidence of
excavation had begun. The           zone. Although this method         down to >13 meters depth,         past earthquakes.

                                                                                                         Many may ask why this trench
                                                                                                         is called the “Ozzie and
                                                                                                         Harriet,” although some may
                                                                                                         have by now guessed that the
                                                                                                         site is located on the property
                                                                                                         once used by the television
                                                                                                         industry in producing the
                                                                                                         famous “Ozzie and Harriet”

                                                                                                         For more information:

                                                                                                                           James F. Dolan
                                                                                                         University of Southern California
                                                                                                            Department of Earth Sciences
                                                                                                                   Los Angeles, CA 90089

                                                                                                               Above: Shoring
                                                                                                               specialist, James Dolan,
                                                                                                               Thomas Rockwell,
                                                                                                               excavator, Donovan
                                                                                                               Stevens, and SDSU's
                                                                                                               Kim Thorup.

                                                                                                               Below: Kim Thorup,
                                                                                                               Thomas Rockwell
                                                                                                               (crouching), James
                                                                                                               Dolan, excavator.
                                                                                                                                             Page 17

Southern California Integrated GPS Network

S everal SCEC organizations are in the process of expand-                 major science goals of the project. A report of the work-
ing continuous Global Positioning System (GPS) station                    shop can be obtained by anonymous FTP from
coverage in southern California. GPS is used to monitor          in /pub/SCEC.
deformation of the earth’s crust and can measure the slow,
quiet movement between earthquakes as well as large                       The network will be used to study the pervasive fault
sudden displacements due to earthquakes. Continuous                       system in southern California, including blind thrust faults.
GPS networks, such as the southern California Permanent                   The primary goals of the network are to: 1) Measure the
Geodetic GPS Array (PGGA), were first implemented to                      interseismic velocity field to 1 mm/yr over a period of five
provide a framework for GPS surveys that were conducted                   years and measure the strain distribution across the region.
relatively infrequently to measure the interseismic velocity              2) Test geologic models and estimate the fraction of strain
field. The PGGA proved useful, however, for both the                      accumulation that is released through earthquakes. 3)
Landers and Northridge earthquakes.                                       Improve our understanding of fault and earthquake
                                                                          mechanics to provide better estimates of seismic hazard in
Following the Northridge earthquake NASA, the United                      the region.
States Geological Survey (USGS), and the National Science
Foundation (NSF) committed funds to expand the Los                        Relevant GPS World Wide Web pages:
Angeles area network from two to 25 stations. SCEC
organizations involved in the oversight and implementa-                   Southern California Earthquake Center
tion of the network include the Jet Propulsion Laboratory,      
Massachusetts Institute of Technology, Scripps Institution                Jet Propulsion Laboratory
of Oceanography, University of California, Los Angeles,         
and the United States Geological Survey (USGS). The new                   Scripps Institution of Oceanography
stations and PGGA are part of the Southern California           
Integrated GPS Network (SCIGN). NASA has committed                        University of California Los Angeles
$1M for 25 stations to be added to the network in 1996 and      
addtional funds are being sought from NASA, NSF, the                      United States Geological Survey
USGS, and other agencies to expand the network to 250           
stations over the next few years. SCEC hosted a workshop
in March of 1995 to design the network and outline the                                                                            Andrea Donnellan

Natural Hazards Seminar Series Schedule

The Jet Propulsion Laboratory invites you to attend the following         the lab. Park in the visitor’s lot and go to Visitor Control. Tell them you
presentations, which are part of a series on natural hazards studies:     are here for the seminar, and ask for directions to building 180, room 101.
                                                                          Allow extra time to clear visitor control. JPL is a NASA facility operated
Wednesday, December 6, 1995 (double header), 2 pm                         by Caltech. NON-US CITIZENS wishing to attend please alert Ron Blom
• Frank Webb, Observations at Mammoth Mountain using GPS                  for obtaining permission to enter the Lab. JPL is a US government facility
• Vince Realmuto, Multispectral Imaging of Volcanic Sulphur Dioxide       and entry permission for citizens of some countries must be obtained in
Thursday, January 4, 1996, 2 pm                                           advance.
• Paul Lundgren, Finite Element Modelling and Earthquakes in Costa
Rica                                                                      For More Information Contact:
• Gilles Peltzer, Radar Interferometry and Tectonics of China
Thursday, May 2, 1996, 2 pm                                               Ronald G. Blom, Ph.D.
• Andrea Donnellan, GPS Results from the Northridge Earthquake            Lead Scientist, Terrestrial Sciences Research Element
                                                                          Jet Propulsion Laboratory, Mail Stop 183-501
IMPORTANT INFO FOR VISITORS:                                              California Institute of Technology
The Jet Propulsion Laboratory (JPL) is located in northwestern Pasadena   4800 Oak Grove Drive
at 4800 Oak Grove Dr. Exit the 210 freeway Berkshire/Oak Grove Drive.”    Pasadena, California 91109-8099 USA
Turn east upon exiting the freeway and make a left turn at Oak Grove      Internet:
Drive (T intersection with Berkshire). Continue up Oak Grove 1/2 mi. to   Telephone 1-818-354-4681
                                                                          Fax 1-818-354-0966
 SC EC     Southern California Earthquake Center                                                                                            Page 18

SCEC Global Science Classroom Activities
SCEC Summer Internship Initiative, 1995, Part 2

S CEC funded 11 students in its second year of supporting               represent SCEC. She presented a poster, The California
undergraduate research. As the program was designed to                  Earthquake Catalog for earthquakes with any magnitude greater
encourage women and underrepresented minorities to                      than or equal to 5.5 between the years 1769 and 1994, and
continue their academic careers and later, enter a profes-              served as a Geosciences Roundtable panelist to discuss
sional career related to earthquake science, SCEC made                  strategies to increase the participation of underrepresented
progress in achieving a balance by sponsoring projects for              groups in the geosciences.
six women and five men. In 1994, nine men and four
women were supported. In addition to the students’ day-                 The program also welcomed the repeat of Rachel
to-day research experiences in the lab and field, many                  Abercrombie and Lisa Grant as outstanding role models
participated in a three-day Technical Orientation staged in             and mentors for the students they supervised. Both had
the Owens Valley in California’s Sierra Nevada region.                  participated in the program in 1994 as Research Advisors.
Students studied geological features of the area, explored              Listed below are the summer interns, their institutions,
evidence of past earthquakes and volcanoes and completed                their research advisors and some of the project titles
a geologic mapping activity.                                            submitted at the completion of the internship. SCEC
                                                                        wishes to thank all university faculty and research advisors
In the late summer, SCEC was invited to sponsor a student               for their support of the students and the program!
(or students) to the NSF Conference on Diversity in the
Scientific and Technical Workforce, September 21-23.                                                                              Curt Abdouch
Mandy Johnson, an Asian American intern, was selected to                                                                               Director
                                                                                                                                SCEC Education

   I=Intern; In=Institution; R=Research Advisor(s); P=Research Project
   I       Windy Brimer                                                 I       Susannah Pazdral
   In      UC Santa Barbara                                             In      Wellesley College
   RA      Marc Kammerling                                              RA      Mark Legg, ACTA, Inc.
   P       Seismic Hazards in the Santa Barbara Channel Using High      P       Mapping the Thirtymile Bank Detachment Fault
           Resolution Seismic Reflection Data and Dated Horizons from
           ODP 893                                                      I       Ryan Smith
                                                                        In      University of Southern California
   I       Andrew Byers                                                 RA      Michelle Robertson
   In      UC Santa Barbara                                             P       In Situ Calibration of the Mainland LABNET Geophones
   RA      Jamie Steidl, Ralph Archuleta
   P       Site-Specific Strong-motion Amplification Factors for the    I       Donovan Stevens
           Southern California Region                                   In      California Institute of Technology
                                                                        RA      James Dolan, USC
   I       Heather Hodgetts
   In      University of Southern California                            I       Carmen von Stein
   RA      Rachel Abercrombie                                           In      Central Washiington University
   P       Microseismicity in the Vicinity of the Cajon Pass Borehole   RA      Lisa Grant, Woodward-Clyde Consultants

   I       Mandy Johnson                                                I       Mike Watkins
   In      University of Southern California                            In      UC Santa Barbara
   RA      David Jackson, UCLA                                          RA      Kim Bak Olsen
   P       The California Earthquake Catalog for Earthquakes with any
           Magnitude Greater Than or Equal to 5.5 between the Years     I       Isabelle Wicks
           1769 and 1994                                                In      University of Southern California
                                                                        RA      Charles Sammis
   I       Jason McKenna                                                P       Observation of Log-Period Activity in the Regional Seismicity Before
   In      UC Santa Barbara                                                     and After the May 2, 1983 M=6 Coalinga Earthquake
   RA      Fabian Bonilla, Jamie Steidl, Ralph Archuleta
                                                                                                                                           Page 19

SCEC Global Science Classroom Activities

 Seismic Sleuths National Leadership                                         Summer VINE Program: A Successful
 Institute                                                                   Experiment in Neighborhood Science
                                                                             Education and Ethnic Diversity
 The 1995 Seismic Sleuths National Leadership Institute was
 conducted Monday, July 17 to Friday, July 21, 1995. Twenty-four
                                                                             About 1,000 elementary students learned about the natural
 people participated in the Institute, which was held at the
                                                                             and built environment (including geology and earthquake
 National Emergency Training Center in Emmitsburg, Maryland.
                                                                             science and safety) in this neighborhood environmental
 Support for the training course was provided by FEMA. Partici-
                                                                             education pilot program. Loosely modeled after the VINE
 pants' backgrounds ranged from secondary classroom teachers to
                                                                             Network, it is an inner city environmental education
 emergency management personnel to museum educational staff,
                                                                             program managed by the North American Association for
 and nationally recognized earthquake research and educational
                                                                             Environmental Education.
 experts. SCEC summoned an experienced team of educational
 specialists and scientists to serve as facilitators for the Institute.
                                                                             The program guided students through Tremor Troop
                                                                             elementary earthquake education activities each week of
 The stated objectives of this Institute were:
                                                                             the program. With the help of 13 Science Activity Leaders,
                                                                             these high school students represented African American,
      To acquaint participants with Seismic Sleuths                          Hispanic American and Asian American ethnic groups.
          earthquake education materials for secondary                       The six-week program was conducted in South Central
          grades 7-12.                                                       inner city Los Angeles Boys and Girls Club and USC
      To acquaint participants with key earthquake science
                                                                             neighborhood school sites. The program was supported
          and seismic safety concepts
      To provide practice in developing National Standards-                  by a combination of funding from the Southern California
          related instructional plans using Seismic Sleuths                  Academy of Sciences, Chevron Oil Company, ARCO,
      To demonstrate the use of Seismic Sleuths as being                     FEMA, the City of Los Angeles Summer Youth Employ-
          revised and aligned with the new National Earth                    ment and Training Program and the USC Neighborhood
          Science Educational Standards                                      Outreach Program. The program also supported four
      To provide practice in conducting Seismic Sleuths                      earth science graduate students as worksite supervisors
          activities                                                         and employed an African American elementary teacher as
      To model the role of Instructors as teaching/learning                  program coordinator.
          facilitators, as recommended by the National
          Science Education Standards                                        The second phase—the development of a small-scale
      To provide opportunities for participants to assemble                  enterprise— may link students to opportunities in
          an earthquake engineering lab model                                earthquake safety kit design, manufacture and distribu-
      To acquaint participants with educational resources                    tion.
          from FEMA and other sources

 Throughout the workshop, scheduled activities and instructional
                                                                             For more information:
 strategies such as field trips, activity demonstrations, practice           Curt Abdouch
 sessions, videofests and “make and take” opportunities assured              Director, SCEC Education
 that all of the above were met.

 Seismic Sleuths Review Panel: The
 SCEC Global Classroom on the                                             ducted in response to feedback received from the field that the
 National Scene                                                           materials needed some revision before being published in final form.
                                                                          SCEC convened a six-member panel in March, 1995 to carry out this
 SCEC’s experience and success in training teachers led to the            mandate. Preliminary and final reports were submitted to FEMA.
 award of a supplemental grant from FEMA to conduct an                    The panel also considered the elements, processes and general daily
 independent review of Seismic Sleuths and the development and            agenda for a three-day and four-day model training workshop. The
 field testing of a model for a training workshop to be used              model was scheduled to be tested in April, but it was mutually
 throughout the nation as well as at additional FEMA training             agreed that it would be used as the format for the 1995 National
 institutes.                                                              Leadership Institute, to be held in Emmitsburg, Maryland, July 17-21.

 Perhaps the most significant activity related to educational             The panel’s most fundamental and potentially far-reaching recom-
 materials and services for secondary teachers to date has been the       mendation was to align Seismic Sleuths with the new National Earth
 review of the Seismic Sleuths materials. The review was con-             Science Education Standards.
 SC EC      Southern California Earthquake Center                                                                                            Page 20

Southern California Seismic Network: Special Report
The 1995 Ridgecrest Earthquake Sequence in Eastern California

The Ridgecrest earthquake           the east and the Sierra Nevada          north to south over a distance          independent data sets suggests
sequence began on 17 August         to the west. The valley floor is        of 12 km, with temporal bursts          that the event may have begun
1995 with a ML5.4 earthquake.       cross cut by a northerly-               in activity. The largest earth-         with normal faulting and
As of October 3, 1995, the          trending mosaic of fault                quake to occur in the valley            quickly evolved into right-
Southern California Seismic         segments that merge towards             itself was a ML4.9 event in             lateral strike-slip faulting.
Network (SCSN) had recorded         the north with the frontal fault        April 1982. It caused some
over 4500 events in the             of the Sierra Nevada or the             ground cracking (Roquemore              The SCSN station coverage in
sequence, with eight events of      rupture zone of the 1872                and Zellmer, 1983) on two               the region is good with about
M≥4.0. These earthquakes are        earthquake. In the south, this          short fault segments.                   10 km average station spacing.
occurring along the eastern         mosaic of segments diffuses                                                     To obtain accurate hypocenters
edge of the Indian Wells Valley     into a broad zone of faulting           The ML5.4 Earthquake of                 we inverted arrival time data
along a small stretch of the        that disappears before it is cut                                                from 250 earthquakes in this
                                                                            17 August 1995
thoroughgoing Eastern               off by the west-striking                                                        sequence for an improved
California Shear Zone (ECSZ).       Garlock fault. The mosaic of            The ML5.4 Ridgecrest earth-             velocity model and a set of
Previous large events within        fault segments consists of north        quake that occurred on 17               corresponding station delays.
the ECSZ include the 1992           to northwest striking, as well          August 1995 was located 11              We used the VELEST program
(MW7.3) Landers earthquake          as a lesser number of north-            miles north of Ridgecrest, on           (Kissling et al., 1994). The final
sequence and the 1872 (M7.6)        east-striking faults, most of           the county boundary between             locations were calculated using
Owens Valley earthquake. The        short length, of less than a            Kern and San Bernardino                 HYPOINVERSE (Klein, 1985)
only large earthquake to occur      kilometer up to 10 km length            Counties. The focal depth of            and focal mechanisms were
near Indian Wells Valley, was       (Figure 1, page 21).                    this event was shallow, or 6 km         determined from first motion
the 1946 Walker Pass (M6.0)                                                 deep, as is common in this              polarities using FPFIT
earthquake on an unknown            During the last three decades           region. This event was felt             (Reasenberg and Oppenheimer,
fault in the Sierra Nevada          the seismicity of this region has       widely in southern California.          1985).
mountains to the west. The          been characterized by swarms            The first motion focal mecha-
ECSZ transfers some of the          of earthquakes, some of which           nism of the ML5.4 earthquake            In the next 5 weeks the ML5.4
relative motion between the         have lasted more than 12                had a dominantly normal-                earthquake was followed by
north America and Pacific           months. These swarms                    faulting mechanism (Figure 2,           over 2,500 aftershocks, 3 of
Plates away from the San            typically have thousands of             page 22). The focal mechanism           which were ML>4 aftershocks.
Andreas fault to the western        small earthquakes and the               derived from regional surface           The first of these larger
Great Basin of the Basin and        largest earthquakes in the              waves, however, showed a                aftershocks occurred on the
Range province.                     magnitude range of 4 to 5. The          more dominant strike-slip               same day while the two later
                                    swarms tend to migrate in               component (H. K. Thio, written          ones occurred on August 29
The Indian Wells Valley is          space. For instance, the                communication, 1995). This              and September 11. The spatial
flanked by the Coso Range to        fourteen-months-long swarm              difference in the focal mecha-
the north, the Argus Range to       in 1980-1981 migrated from              nism derived from the two                    See "Ridgecrest" on Page 21

                      Earthquake Faults in Southern California

                      The most recent source of information about faults in California is the Fault Activity Map of California.
                      Copies may be obtained by mailing a check in the amount of $20, which covers the map and shipping,
                      with your written request for Map #GDM-006, to:

                                                     California Division of Mines and Geology
                                                                    PO Box 2980
                                                            Sacramento, CA 95812-2980
                                                                                                                                            Page 21

Ridgecrest continued from Page 20 ...

distribution of the immediate      from the other events, with           This sequence has shown                events (M>4) has been accom-
aftershocks suggests that the      left-lateral strike-slip faulting     significant temporal variability       panied by a burst of smaller
ML5.4 earthquake occurred on       on a north-striking plane             in its distribution in time,           earthquakes, but the M3
a north-northwest-striking         (Figure 3, page 24). This             space, and magnitude. The              aftershocks have also shown a
fault. The two later ML>4          mechanism and the location of         locations of the sequence              notable temporal clustering.
aftershocks occurred to the        the event, six km to the              events have migrated with              This clustering has lead to a
northeast of the mainshock and     northeast of the main part of         time, extending from the               significant variability in the b-
were followed by events            the sequence, suggests that a         original aftershock zone to
forming a northeast lineation,     fourth fault was activated in         both the northeast and
suggesting that they activated     this event.                           southeast. Each of the larger              See "Ridgecrest" on Page 22
a separate northeast-striking
fault (Figure 2). In addition, a
vertical north-striking group of
aftershocks to the southwest of
the mainshock hypocenter
suggests that three separate
faults might be involved in this
part of the sequence (Figure 2).

The ML5.8 Earthquake of 20
September 1995

The ML5.8 earthquake occurred
about 2 km to the south-
southeast of the epicenter of
the ML5.4 earthquake at a focal
depth of 5 km. It had a strike-
slip focal mechanism with a
north-northwest striking nodal
plane, aligned with the strike
of the aftershock distribution.
The aftershocks form a 7-km-
long distribution that defines
an almost vertical plane in the
depth range of 3 to 11 km
(Figure 3). The strike of this
distribution coincides with that
of the ML5.4 event so the ML5.8
mainshock may be occurring
on a southeastward extension
of the ML5.4 earthquake’s fault.

Over 1,900 aftershocks have
been recorded in the two
weeks since the ML5.8
mainshock. The largest was a
                                              Figure 1. Overview of seismicity in Indian Wells Valley recorded by the Southern California
ML4.9 event on September 24.                  Seismic Network from 1980 to 1995. Symbol size is scaled with magnitude. The swarms
This event had a focal mecha-                 of 1980-1981, 1992, and the 1995 sequence are labeled with the year. The box indicates
nism significantly different                  the location of Figures 2 and 3. The straight lines are the county boundaries.
SC EC     Southern California Earthquake Center                       Page 22

Ridgecrest continued from Page 21 ...

    Figure 2.

    (A) Map of the epicenters from 16 August to 19 September, 1995.
    Symbol size is scaled with magnitude. Mapped Holocene faults
    are also shown. The M5.4 earthquake and M>4 aftershocks are
    indicated by their lower hemisphere focal mechanisms.

    (B) Strike-normal cross section and

    (C) strike-parallel cross section.
                                                                                                                                Page 23

Ridgecrest continued from Page 22 ...

value of the sequence with         cracking revealed evidence of      Angeles, meant that damage        (AMOES) and located at sites
time. The original aftershocks     up to 2 mm of right-slip as        was confined to Ridgecrest and    of the Pacific Bell Company are
to the ML5.4 event had a           observed in pebbles pulled         its vicinity. The Caltech US      now operating in southern
moderately high b-value of         away their matrix on the           Geological Survey Broadcast of    California. These stations
1.13 ± 0.07. In the first day of   opposite side of the cracks.       Earthquakes (CUBE) reported       provide near-real time esti-
aftershocks to the ML5.8, the b-   The areas closest to the           the location and preliminary      mates of strong ground
value went down to 0.90 ± 0.08     epicenter and areas to the east    magnitude of both mainshocks      shaking. The data are trans-
(the average for Californian       where the fault plane (deter-      within 3 minutes of their         mitted from the remote sites
aftershocks), but since then it    mined from seismicity) would       occurrence. This information      using frame relay digital
has returned to a higher value     project to the surface was also    was used by local utilities and   technology under a California
(1.10±.10).                        investigated but only ran-         transportation companies to       Research and Educational
                                   domly oriented cracks inter-       determine the scope of their      Foundation (CalREN) grant
                                   preted to be caused by shaking     deployment of field crews         from Pacific Bell.
Geological Field
Investigations                        "Earthquake information from the                                  The ML5.8 earthquake pro-
                                      SCSN is available on the World Wide                               vided the first test of the new
The Ridgecrest earthquakes                                                                              enhancements to SCSN and
may have caused triggered slip
                                      Web[and                           CUBE for strong ground
on fault segments within the          was] accessed by thousands of users                               motion monitoring. Contours
Airport Lake fault zone               during August and September."                                     of measured peak horizontal
(Roquemore and Zellmer,                                                                                 and vertical accelerations are
1986), outside of the epicentral                                                                        shown in Figure 4. Presumably
and aftershock areas. A short      and settlement was observed.       following the earthquake. The     the ground shaking was
(3km), northsouth striking fault                                      CUBE system broadcasts            highest at the epicenter and
segment, located approxi-          Following the September 20,        earthquake information            decreased rapidly with
mately 3 km to the northwest       1995, M5.8 earthquake, the         automatically via commercial      distance. Because of the sparse
of the epicentral region           region was again investigated      paging to both belt pagers and    distribution of high-dynamic
experienced surface cracking       for surface rupture. The same      pagers connected to computers     range stations in eastern
possibly related to surface        fault segment within the           that can display on a map the     California the contours of
rupture in both the August 17      Airport Lake fault zone            location and magnitude.           ground motion are not exactly
and September 20 events.           experienced more extensive         Earthquake information from       centered on the epicenter.
                                   cracking. Evidence for surface     the SCSN that is available on     Instead large peak values
The epicentral region of the       rupture was observed in            the World Wide Web (http://       caused by local site amplifica-
August 17 and September 20,        several locations along the pre-,           tion effect the pattern of
1995 Ridgecrest earthquakes        existing fault scarp. A maxi-      including near-real time          ground motions. The contours
was investigated for potential     mum vertical displacement of 1     locations and magnitudes and      that are well constrained in the
surface rupture. Following the     cm was measured near the           the weekly bulletin, were         Los Angeles to San Bernardino
August 17 event a highly           middle of the rupture zone.        accessed by thousands of users    urban corridor also show how
fragmented line of surface         Also near the middle of the        during August and September.      the sedimentary basins locally
cracking was located along a       rupture zone, a maximum of                                           amplify the ground shaking.
mapped fault segment within        8mm of right-slip was mea-         In the last few years, Caltech    These new data demonstrate
the Airport Lake fault zone.       sured.                             and the US Geological Survey      that emerging technologies
The Airport Lake fault zone is a                                      have been working to improve      now are becoming available to
broad zone of northsouth           Rapid Notification And             the capability of the SCSN to     enhance the capabilities of
striking normal and oblique                                           provide quick estimates of the    regional networks to process
                                   Ground Motion
slip fault segments. The cracks                                       location of strong shaking to     and quickly distribute informa-
were generally 1 to 2 meters       The ML5.8 Ridgecrest earth-        emergency management              tion about ground accelera-
long and separated by several      quake is the largest earthquake    officials. Eighteen broad-band    tions. The reliability of the
meters over a total length of      to strike southern California      TERRAscope stations, eight        information, however will be
less than 1 km. Two parallel       since the 1994 (Mw6.7)             analog SCSN stations with         strongly dependent on
cracks separated by about 50       Northridge earthquake. It was      strong motion sensors, and ten    adequate station distribution.
cm formed along some of the        widely felt over southern          new strong motion sensors,
segments. Other segments           California, even though its        deployed as part of the
showed en echelon patterns.        location, in the desert 150        Automated Monitoring of
Close inspection of the            kilometers north of Los            Strong Ground Motions Project
                                                                                                            See "Ridgecrest" on Page 24
SC EC   Southern California Earthquake Center            Page 24

Ridgecrest continued from Page 23 ...

      Figure 3.

      (A) Map of the epicenters from 20 September to 3
      October, 1995. Mapped Holocene faults are also
      shown. The M5.8 earthquake and M>=4 aftershocks
      are indicated by their lower hemisphere focal

      (B) Strike-normal cross section and

      (C) strike-parallel cross section.
                                                                                                                                             Page 25

Ridgecrest continued from Page 24 ...                                                                               Discussion

                                                                                                                    The most notable feature of the
                                                                                                                    1995 Ridgecrest sequence is the
                                                                                                                    multiple faults involved in the
                                                                                                                    sequence and the spatial
                                                                                                                    migration of the aftershocks
                                                                                                                    with time. This spatial
                                                                                                                    migration has been characteris-
                                                                                                                    tic of previous swarms in the
                                                                                                                    general region (1981-1992
                                                                                                                    Indian Wells Valley, 1983
                                                                                                                    Durrwood, 1990 (Jones and
                                                                                                                    Dollar, 1986) ), but these
                                                                                                                    mainshocks were smaller than
                                                                                                                    those in the 1995 sequence.
                                                                                                                    The only other recent, large,
  Figure 4. (A) Vertical and (B) horizontal peak accelerations in cm/sec2 from the M5.8 earthquake                  southern Californian earth-
  (epicenter indicated by solid diamond). The ground motions are affected by distance from the epicenter            quake with similarly migrating
  and local site effects. The open squares are TERRAscope stations while the filled circles are analog              aftershocks was the 1992 M6.1
  SCSN stations and digital AMOES/CalREN stations with strong motion sensors.                                       Joshua Tree earthquake. That
                                                                                                                    event was also in the ECSZ and
                                                                                                                    was a preshock to the Mw7.3
                                                                                                                    Landers earthquake
                                                                                                                    (Hauksson, et al., 1993).
     Acknowledgments. We are grateful to the seismic analysts of Caltech and the USGS for
     quick and competent processing of the earthquake data. We thank K. Sieh and B.                                 Although the ML5.8 Ridgecrest
     Wernicke for geological insights. We thank Frank Monastero and Allan Katzenstein for                           earthquake is the largest
     assistance with the field effort. This research was partially supported by USGS grant                          recorded in this region,
     1434-94-G-2440, USGS cooperative agreement 1434-92-A-0960, and NSF grant 94-16119                              earthquakes of larger magni-
     to Caltech. Southern California Earthquake Center publication 226. Contribution 5604,                          tude are possible.
     Division of Geological and Planetary Sciences, California Institute of Technology,
                                                                                                                                    Egill Hauksson
                                                                                                                                       Kate Hutton
                                                                                                                                   Hiroo Kanamori
                                                                                                                         Seismological Laboratory
                                                                                                                                         Lucile Jones
        •Ellsworth, W. L., 1990, Earthquake history,         a program for VAX and PC350 computers to                                     James Mori
        1769-1989, in The San Andreas Fault System, Cali-    solve for earthquake locations, U.S. Geol. Surv.,                          Susan Hough
        fornia, edited by R. Wallace, U. S. Government       Open-File Rep., 85-515, Menlo Park, California, 24
        Printing Office, Washington DC, 153-188.             pp., 1985.
        •Hauksson, E., L. M. Jones, K. Hutton, and D.        •Reasenberg, P., and D. Oppenheimer, FPFIT,
        Eberhart Phillips, The 1992 Landers earthquake       FPPLOT and FPPAGE: Fortran computer pro-                              Glenn Roquemore
        sequence: Seismological observations, J.             grams for calculating and displaying earthquake                  Irvine Valley College
        Geophys. Res., 98, 19,835-19,858, 1993.              fault-plane solutions, U.S. Geol. Surv. Open-File
        •Jones, L. M., and R. S. Dollar, Evidence for ba-    Report, 85-739, 109 pp., 1985.
        sin-and-range extensional tectonics in the Sierra    •Roquemore, G.R., and Zellmer, J.T., 1983,
        Nevada: The Durrwood Meadows swarm,                  Ground cracking associated with 1982 magni-
        Tulare County, California (1983-1984), Bul. Seis.    tude 5.2 Indian Wells Valley earthquake, Inyo
        Soc. Am., 76, 439-461, 1986.                         County, California: California Geology, 36, no. 9,p.
        •Kissling, E., W. L. Ellsworth, D. Eberhart-         197-200.                                                 Note: This article has been
        Phillips, and U. Kradolfer, Initial reference mod-   •Roquemore, G.R., and J.T. Zellmer, 1986, NWC            submitted to Seismological
        els in local earthquake tomography: J. Geophys.      Active Fault Map Series, Naval Weapons Cen-              Research Letters and is also
        Res., 99, 19,635-19,646, 1994.                       ter Technical Series, TS 82-69, China Lake, Cali-        listed among SCEC's
        •Klein, F. W., User’s guide to HYPOINVERSE,          fornia.                                                  Publications as No. 226.
SC EC     Southern California Earthquake Center                                                                          Page 26

Earthquake Information Resources On Line

   SCEC World Wide Web Home Page                                    Other WWW Sites for Exploration

                    SCEC WWW URL                                    • Yahoo: General internet index
                                                                    • Internet Search (via Netscape Corporation)
 Cruising the Internet?            descriptions of each             • WWW Viewer Test Page (ensure that your browser
 Check out the new SCEC            Working Group's research         will work)
 WWW Home Page.                    to date.               

 Here is a sample list of          The page also features links     Earthquakes and Seismology
 what you'll see:                  to:                              • Yahoo - Earthquakes section
 Home Page:                        • SCEC Core Institutions         Disasters/Earthquakes
 "What is SCEC?"--a                • SCEC Infrastructure            • Seismo-surfing the Internet
 summary of the Center's           Facilities--such as the SCEC
 history and purpose,              Data Center at Caltech; the
 including a description of        SCEC GPS Centers at
                                                                    • USGS - Menlo Park (Earthquake info, past and
 the Master Model concept.         UCLA and Scripps                 current)
 "Formal Mission"--Mission         Oceanographic Institute; or
 statement and list of             and the Portable Broad-          • Recent Quakes (with a great map viewer)
 Working Groups and                band Instrument Center at
 Leaders, with links to more       UCSB.                            • Kobe shaking (color photo of shaking intensity)
 detailed descriptions of the      • SCEC Outreach Pro-   
 research conducted by each        grams                            kobeshake.html
 of the groups.                    • SCEC Products--such as
 "Organization"--a classic         the earthquake hazard            Engineering and Preparedness
 organizational chart which        analysis map; the Quarterly
                                                                    • NCEER (National Center for Earthquake Engi-
 shows, at a glance, the           Newsletter; and SCEC
 structure of the Center.          Publications List.
                                                                    neering Research)
 "Research"--a layer acces-        • "Surfing the Net for 
 sible through the home            Earthquake Data"                 • Earthquake Engineering Research Center (EERC)
 page and the "Mission"                                   
 page, with detailed                                 Jill Andrews   • Structural Engineers Association of California
                                                                    • Earthquake Hazard Maps (ABAG Searchable
                 SCEC on the Internet                               • Emergency Preparedness Info Exchange
 SCEC Knowledge Transfer and Education Programs                     • Federal Emergency Management Agency (FEMA)
 are now reachable via electronic mail.                   
                                                                    • California Office of Emergency Services
 Ask general questions, make requests, send us            
 information for use in our resource center or for                  • Other Civil Engineering Servers
 consideration for publishing in the next newsletter.     

                                                                     Peter Clark and Katie Frohmberg
                                                                                                                   UC Berkeley
                                                                                       Earthquake Engineering Research Center
                                                                                                                         Page 27

           Southern California                                       SCEC Board of Directors
           Earthquake Center                                Keiiti Aki, Chairman              Bernard Minster, Vice Chairman
             Administration                          University of Southern California      Scripps Institute of Oceanography
                                                              Ralph Archuleta               University of California, San Diego
       Science Director - Keiiti Aki                      University of California,                   David Jackson
   Executive Director - Thomas Henyey                          Santa Barbara               University of California, Los Angeles
     Administration - John McRaney                            Robert Clayton                         Leonardo Seeber
        Education - Curt Abdouch                     California Institute of Technology            Columbia University
Engineering Applications - Geoffrey Martin                                         James Mori
    Knowledge Transfer - Jill Andrews                                    United States Geological Survey

                                                                       To Subscribe
SCEC Activities Calendar
 November 1995
                                                                        to the SCEC
 9 -10     SCEC-sponsored Insurance Industry Workshop.
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                                                                          Write, Telephone, or fax to
 December 1995
 6-8       FEMA's First Biennial National Mitigation                      Southern California Earthquake Center
           Conference, Washington, DC. See advertise-                     University of Southern California
           ment, page 9.
                                                                          University Park
 11-15     American Geophysical Union annual meeting,                     Los Angeles, CA 90089-0740
           San Francisco, CA.                                             Tel: 213/740-5843
                                                                          Fax: 213/740-0011
 January 1996
 20        Association of Engineering Geologists,
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        SCEC has added a new telephone number. Call                 
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                                                                   SC EC
Inside this issue:                                                                                        SCEC Quarterly Newsletter
                                                               SCEC Quarterly Newsletter is published quarterly by the Southern
                                                               California Earthquake Center, University of Southern California,
Feature Articles                                               University Park, Los Angeles, CA 90089-0740, USA, telephone
                                                               213/740-1560 or 213/740-5843, fax 213/740-0011, e-mail:
                                                      Please send requests for subscriptions and
        LARSE Report                                 Page 1    address changes to the attention of the editor.
        What is SCEC?                                Page 2
        So. Calif. Integrated GPS Network            Page 17                           Science Director: Keiiti Aki
                                                                                       Executive Director: Thomas Henyey
                                                                                       Administration Director: John McRaney
                                                                                       Engineering Director: Geoffrey Martin
SCEC Departments                                                                       Education Director: Curt Abdouch
                                                                                       Knowledge Transfer Director: Jill Andrews

        From the Center Directors                    Page 2
                                                               Editor, Writer, and Production Artist: Jill Andrews
        Quarter Fault                                Page 8
        Recent Publications                          Page 14
                                                               Contributing Writers:                                 Photographs and Figures:
        Activities Reports:                                    Curt Abdouch, SCEC                                    M. Forrest (pp. 8, 9, 10, 11,12, 15, 16)
         SCEC Annual Meeting                         Page 10   Keiiti Aki, USC/SCEC                                  G. Fuis (pp. 1, 4, 5, 6)
         Hollywood Fault Research                    Page 15   James F. Dolan, USC/SCEC                              E. Hauksson (pp. 21, 22, 24, 25)
         Visit with a SCEC Scientist                 Page 12   Andrea Donnellan, Caltech/JPL
        Global Science Classroom News                Page 18   Michael Forrest, USC
                                                               Gary S. Fuis, USGS                                    Copy Editor
        SCSN Special Report: Ridgecrest              Page 20
                                                               Egill Hauksson, Caltech SCSN                          Rene Kirby, USC
        Earthquake Info Resources On Line            Page 26   Thomas Henyey, SCEC
        Calendar                                     Page 27
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 SC EC       University of Southern California                                                                         Non-Profit Organization
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