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STATE OF CALIF Powered By Docstoc
					                                                                                                                                                                                          STATE OF CALIFORNIA, EDMUND G. BROWN Jr., GOVERNOR
CALIFORNIA GEOLOGICAL SURVEY                                                                                                                                                   THE NATURAL RESOURCES AGENCY, JOHN LAIRD, SECRETARY FOR NATURAL RESOURCES                                                                                                                                                                                           MAP SHEET 58
JOHN G. PARRISH, PH.D., STATE GEOLOGIST                                                                                                                                              DEPARTMENT OF CONSERVATION, DEREK CHERNOW, ACTING DIRECTOR                                                                                                                                                           SUSCEPTIBILITY TO DEEP-SEATED LANDSLIDES IN CALIFORNIA




             Susceptibility to Deep-Seated Landslides in California
                                                                                                                                                                                                                                    2011
                                                                                                                                                                                C. J. Wills, F. G. Perez and C. I. Gutierrez
   This map shows the relative likelihood of deep landsliding based on regional estimates of rock strength and steepness of slopes. On the most basic level, weak
   rocks and steep slopes are more likely to generate landslides. The map uses detailed information on the location of past landslides, the location and relative
   strength of rock units, and steepness of slope in a methodology developed by Wilson and Keefer (1985). The result shows the distribution of one very important
   component of landslide hazard. It is intended to provide infrastructure owners, emergency planners and the public with a general overview of where landslides
   are more likely. The map does not include information on landslide triggering events, such as rainstorms or earthquake shaking, nor does it address susceptibility
   to shallow landslides such as debris flows. This map is not appropriate for evaluation of landslide potential at any specific site.
                                                                                                          124                          123                                122                                121                              120
                                                                                             42
                                                                                                                                                                                                                                                    42



      How this map was prepared
                                                                                                              Del                                                                                                                                                                                                          Average Annual Rainfall                                                                                             Earthquake Shaking Potential
                                                                                                             Norte                                                                                                 Modoc
     Landslide inventory: All previously mapped deep-seated                                                                                                                                                                                                                                                                               Over 100
     landslides that are available in digital format are assigned                                                                            Siskiyou
                                                                                                                                                                                                                                                                                                                                             85
     the lowest value of rock strength. Note that digital landslide




                                                                                                                                                                                                                                                                                                                                                                                                                                                                        Increasing intensity
     inventory maps are only available for specific counties,                                                                                                                                                                                                                                                                                30
     shown in yellow, and may cover only part of those counties.                                                                                                                                                                                                                                                                             15

                                                                                                                                                                                                                                                                                                                                             10
                                                                                                 41                                                                                                                                                 41                                                                                           5

                                                                                                                                                                                                                                                                                                                                              0
                                                                                                                                                                                                                                                                                                                                           inches
                                                                                                                                                                       Shasta                                        Lassen
                                                                                                                          Trinity
                                                                    ~ 57, 000                           Humboldt
                                                                      Deep
                                                                   Landslides



                                                                                                  40

                                                                                                       124
                                                                                                                                                              Tehama

                                                                                                                                                                                                                     Plumas
                                                                                                                                                                                                                                                     40                               Ü                                                                                                                 Ü
                                                                                                                                                                                                                                                                                                                                                                                                    0     50    100          200
                                                                                                                                                                                                                                                                                  0    50    100         200                                                                                                                    Kilom eter s
                                                                                                                                                                                                                                                                                                            Kilom eter s




                                                                                                                     Mendocino                                                      Butte                                      Sierra
                                                                                                                                                       Glenn                                                                                                       SOURCE: Fire and Resources Assessment Program, California Department of Forestry and Fire                              SOURCE: Branum, D., Harmsen, S., Kalkan, E., Petersen, M., and Wills, C., 2008, Earthquake
                                                                                                                                                                                                                                                                   Protection (http://frap.cdf.ca.gov)                                                                                    Shaking Potential for California, California Geological Survey Map Sheet 48 (Revised 2008).




                     Ü
                                                                                                                                                                                                                              Nevada

                                                                                                                                                            Colusa                                                              Placer                             Next steps, from landslide susceptibility to landslide potential: Landslides can be triggered by
                                                                                                                                                                                             Yuba
                 0        50        100         200
                                                   Kilom eter s
                                                                                                                39
                                                                                                                                               Lake
                                                                                                                                                                                                                                                         39
                                                                                                                                                                                                                                                                     rainfall, by earthquake shaking, or other factors. Additionally, this map does not include
                                                                                                                                                                                    Sutter                                                                               susceptibility to debris flows, a very fluid, fast-moving form of landslide which typically is
                                                                                                                                                                          Yolo
                                                                                                                                                                                                                        El Dorado                                           triggered by intense rainfall. A complete map of landslide potential would consider the
                                                                                                                                                                                                                                                                                 increase in landslide hazard, including debris flow hazard, with higher potential
     SOURCE: Digital maps compiled from USGS, and from CGS’s Landslide Hazard Identification, Seismic
     Hazard Zoning and Forest and Watershed Geology Programs.                                                                Sonoma
                                                                                                                                                             Napa                                                                                        Alpine
                                                                                                                                                                                                                                                                                    rainfall and with higher potential earthquake shaking. Average annual rainfall is
                                                                                                                                                                                                                   Amador
                                                                                                                                                                                                                                                                                        higher in the northern Coast Ranges and northern Sierra Nevada than in the
                                                                                                                                                                                                                                                                                       119
     Geology: A general statewide geologic map is augmented with detailed geologic
     maps covering the most populous parts of the state to create a complete map. The                                                                                                        Sacramento
     physical properties of the geologic units were interpreted from the descriptions
                                                                                                                                                                            Solano                                                                                                          rest of the state and potential earthquake shaking is higher in the coastal
     on the geologic maps to determine the rock strength units.                                                                                                                                                      Calaveras
                                                                                                                            38
                                                                                                                                              Marin                                                                                                                                             regions. Although we cannot currently combine these factors to produce
                                                                                                                                                                                                                                                                                                                 38


                                                                                                                                 123                                Contra Costa
                                                                                                                                                                                              San Joaquin
                                                                                                                                                                                                                                         Tuolumne
                                                                                                                                                                                                                                                                              Mono                  a landslide potential map, the convergence of factors suggests higher
                                                                                                                                          San                                                                                                                                                           landslide potential in the northern Coast Ranges than in other
                                                                                                                                       Francisco
                                                                                                                                                                                                                                                                                                           regions of the state.
                                                                                                                                                                                                                                                                                                                                    118



                                                                                                                                                                          Alameda                      Stanislaus                               Mariposa
                                                                             ~ 120, 000
                                                                                                                                                San
                                                                            Geologic Units
                                                                                                                                               Mateo
                                                                                                                                                                             Santa Clara
                                                                                                                                                                                                                      Merced
                                                                                                                                                                                                                                                                                                                                                                    117

                                                                                                                                                               37                                                                            Madera                                                                                                                       37

                                                                                                                                                             Santa       122
                                                                                                                                                             Cruz

                                                                                                                                                                                                                                                               Fresno                                                                                 Inyo
                                                                                                                                                                                                    San Benito




                     Ü                                                                                                                                                                             Monterey
                                                                                                                                                                                                                                                                                              Tulare                                                                                                                   116



                                                                                                                                                                                                                                                                                                                                                                                                                                   36

             0           50        100         200
                                                  Kilom eter s
                                                                                                                                                                                        36
                                                                                                                                                                                                                                                               Kings


      SOURCE: Digital geologic maps of various scales: 1:100,000 scale geologic maps of the Long Beach,
      Los Angeles, Oceanside, San Bernardino, San Diego, Santa Ana, and Santa Barbara 30 x 60 minute
      quadrangles; the regional simplified map of Wills and Clahan (2006); the 1:24,000 scale geologic maps
      of several 7.5 minute quadrangles; and the map of Graymer (2008) of the San Francisco Bay area.
                                                                                                                                                                                                                                                                                                                                                                                                                                                                        115


                                                                                                                                                                                                                                                                                                         Kern
     Rock strength: A relative rating of rock strength, a measure of resistance to                                                                                                                             121


     landsliding, was developed from the geologic and landslide inventory maps.                                                                                                                                               San Luis Obispo
     Each geologic unit was classified into one of three rock strength categories                                                                                                                                                                                                                                                                                                                                                                                                                    35

     according to the methodology of Wieckzorek (1985). Crystalline rocks and well
     cemented sandstones are placed in the highest rock strength unit, weakly                                                                                                                                                                                                                                                                                                                           San Bernardino
                                                                                                                                                                                                                         35
     cemented sandstones in an intermediate unit, and shale, claystone, pre-existing
     landslides and unconsolidated surficial units in the weakest unit.                                                                          ROCK STRENGTH
                                                                                                                                                              1         2          3                                                           Santa Barbara

                                                                                                                                                                                                                                                                                      Ventura
                                                                                                                                                  1            0         0         0                                                                                                                                          Los Angeles
                                                                                1       2     3
                                                                                                                                   C LA S S




                                                                                                                                                                                                                                                         120


                                                                                    decreasing                                                    2            0         V        VII
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          34
                                                                                     strength
                                                                                                                                                  3            0         V        VII
                                                                                                                                                                                                                                                                                               119

                                                                                                                                                                                                                                                                                                                                                                                                                       Riverside
                                                                                                                                                  4           III      VIII        IX
                                                                                                                                                                                                                                                                                                                                                 Orange
                                                                                                                                                  5
                                                                                                                                   S L O P E




                                                                                                                                                              VI        IX         X                                                                                                                                                       118




                                                                                                                                                  6          VII        IX         X

                                                                                                                                                  7          VIII       IX         X                                                                                                                                                                                                                                                                           Imperial                                     33




                         Ü
                                                                                                                                                                                                                                                                                                                                                                                           San Diego

                                                                                                                                                  8
                                                                                                                                                                                                                                                                                                                                                                   33

                                                                                                                                                             VIII       IX         X
                                                                                                                                                                                                    Landslide susceptibility: Rock strength and slope are
                                                                                                                                           LANDSLIDE
                 0            50    100          200                                                                                                                                                                                                                                                                                                                                                                                                                                           115
                                                    Kilom eter s
                                                                                                                                                                                                    combined according to the methodology of Wilson and Keefer (1985) as                                                                                                                                                             116


                                                                                                                                         SUSCEPTIBILITY                                             implemented by Ponti et al (2008) to create classes of landslide                                                                                                                117

                                                                                                                                                                                                    susceptibility. These classes express the generalization that on very low                                                                                                   References:
     Slope: The slope gradient was computed from the 10-m grid of elevation values
     from the 2009 National Elevation Dataset (NED). Slope values were then
                                                                                                                                            CLASSES                                                 slopes, landslide susceptibility is low even in weak materials, and that
                                                                                                                                                                                                                                                                                                                                                                                Graymer, R.W., Moring, B.C., Saucedo, G.J., Wentworth, C.M., Brabb, E.E., and Knudsen K.L., 2006, Geologic Map of
                                                                                                                                                                                                                                                                                                                                                                                the San Francisco Bay Region: U.S. Geological Survey Scientific Investigations Map 2918
     grouped into eight slope classes ranging from nearly flat (less than three
     degrees) to very steep (greater than 40 degrees).                                                                                          (   0 III V V I V II V III IX X
                                                                                                                                                                                        )           landslide susceptibility increases with slope and in weaker rocks. Very
                                                                                                                                                                                                    high landslide susceptibility, classes VIII, IX, and X, includes very steep
                                                                                                                                                                                                                                                                                                                                                                                Ponti, D.J., Tinsley, J.C. III, Treiman, J.A., and Seligson, H., 2008, Ground Deformation, section 3c in Jones, L. M.,
                                                                                                                                                                                                                                                                                                                                                                                Bernknopf, R., Cox, D., Goltz, J., Hudnut, K., Mileti, D., Perry, S., Ponti, D., Porter, K., Reichle, M., Seligson, H., Shoaf,
                                                                                                                                                                                                                                                                                                                                                                                K., Treiman, J., and Wein, A., 2008, The ShakeOut Scenario: U.S. Geological Survey Open-File Report 2008-1150 and
                                                                                         1        < 3                                                  increasing susceptibility                                                                                                                                                                                                California Geological Survey Preliminary Report 25 http://pubs.usgs.gov/of/2008/1150/.


                                                                                         2
                                                                                                                                                                                                    slopes in hard rocks and moderate to very steep slopes in weak rocks.                                                                                                       Spiker, E.C. and Gori, P., 2003, National landslide hazards mitigation strategy : a framework for loss reduction:
                                                                                                 3-5                                                                                                                                                                                                                                                                            U.S.Geological Survey Circular 1244, 56 p.
                                                                                                                                                                                                                                                                                                                                                                                Wieczorek, G.F., R.C. Wilson, R.C., and E.L. Harp, 1985. Map Showing Slope Instability during Earthquakes in San Mateo
                                                                                         3       5 - 10                                                                                                                                                                                                                                                                         County, California. U.S. Geological Survey Miscellaneous Investigations Series Map I-1257-E.
                                                                      Angle              4   10 - 15                                                                                                                                                                                                                                                                            Wills,C.J. and Clahan, K.B., 2006, Developing a map of geologically defined site-conditions categories for California:
                                                                     (degrees)           5   15 - 20
                                                                                                                                                                                                                                Landslide Overview Map of the Conterminous United States                                                                                        Bulletin of the Seismological Society of America, V. 96 p. 1483 – 1501.
                                                                                                                                                                                                                                                                                                                                                                                Wilson, R.C., and Keefer, D.K., 1985, Predicting areal limits of earthquake-induced landsliding, in J.I. Ziony, editor,
                                                                                                                                                                                                                                                                                                                                                                                Evaluating earthquake hazards in the Los Angeles region-an earth-science perspective: U.S. Geological Survey Professional
                                                                                         6   20 - 30                             Landslide losses: California has a                                                                                                                                                                                                             Paper 1360, p. 317-345.

                                                                                         7   30 - 40                             substantial share of the nation’s                                                                                                                                                                                                              Acknowledgments: Special thanks to our colleagues at CGS: Dave Branum, Tim McCrink, Teri McGuire, Bob
                                                                                                                                                                                                                                                                                                                                                                                Moskovitz, Chuck Real, and Pete Roffers; and to Dino Bellugi of UC Berkeley and Dave Strong of USGS who
                                                                                         8       > 40                            landslide risk because of high                                                                                                                                                                                                                 processed and reprojected the original Geographic NED into UTM NED.


                                                                                                                                 population and concentration
                                                                                                                                 of infrastructure in areas with
                                                                                                                                 substantial landslide hazard.
                                                                                                                                 Landslides cause an estimated

                         Ü
                                                                                                                                 25 to 50 deaths and over $2 billion
                                                                                                                                 damage per year in the United States
                     0        50     100
                                                                                                                                 (Spiker and Gori, 2003). This map of
                                                 200
                                                    Kilom eter s
                                                                                                                                 landslide susceptibility may be used
      SOURCE: 2009 National Elevation Dataset (NED) produced and distributed by USGS                                             to estimate where in California                                                              Susceptibility/Incidence                                                                                               Incidence
      (http://ned.usgs.gov) with the following data specifications:
       Data Type:                            Floating Point                 Vertical units:             Meters                   landslide losses are most likely to be                                                              High/Moderate                                                                                                      High
       Projection:
       Datum:
                                               Geographic
                                                   NAD83
                                                                            Spheroid:
                                                                            Tile size:
                                                                                                    GRS 1980
                                                                                               1 deg. by 1 deg.                  concentrated.                                                                                       Moderate/Low
                                                                                                                                                                                                                                     High/Low
                                                                                                                                                                                                                                                                                                                                                        Moderate
                                                                                                                                                                                                                                                                                                                                                        Low                         www.conservation.ca.gov/cgs                                                      www.usgs.gov
                                                                            Format: ArcGRID and GRIDFLOAT                                                                                                                                                                                            USGS Professional Paper 1183
       Horizontal units:                   Decimal Degree
                                                                                                                                                                                                                                                                                                                                                                               Copyright © 2011 by the California Geological Survey. All rights reserved. No part of this publication may be reproduced without
                                                                                                                                                                                                                                                                                                                                                                               the written consent of the California Geological Survey.
                                                                                                                                             Professional Licenses and Certifications: C. Wills - PG No. 4379, CEG No. 1423; F. Perez - PG No. 6972, Mapping Scientist, Remote Sensing No. R136RS (ASPRS); C. Gutierrez - PG No. 8686                                          “The California Department of Conservation makes no warranties as to the suitability of this product for any particular purpose.”

				
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