Interferometric SAR by jizhen1947


									Here is interesting stress plot.

Figure 10.21: Aftershocks induced by
earthquake stress. The locations of small
aftershocks of a 1992 EQ in Joshua Tree, CA.
Red and yellow indicate where a computer
model predicts increased stress after the EQ.
Purple and blue indicate stress decreases after
the EQ. Changes in stress are small. White
bar is the ruptured fault trace.

Imagine the possibilities of
understanding EQs if we could
measure the subtle ground
deformations resulting from the
mainshock and the aftershocks.
What if we could create an image of
the ground deformation, essentially
with “seismometers” not connected
to the earth?
  This is the Landers EQ in
  CA. June 28th, 1992. A
  right lateral strike slip fault.
  This radar interferogram depicts
  motion occurring during the 1992
  Landers earthquake in southern
  California. These data were acquired
  by the ERS-1 satellite in orbit 500
  miles above the earth, and cover an
  area approximately 30 by 50 miles in
  size. Each color "fringe" represents
  2.8 cm of ground deformation that
  occurred during the earthquake, and
  shows how the Earth's crust
  readjusted itself to a new distribution
  of forces along the fault (shown in
  black) when the earthquake struck.

figure not in book
How Synthetic Aperture Radar Data Are Collected
 Observed interferogram calculated from
 ERS-1 SAR images taken before (April
 24, 1992) and after (June 18, 1993) the
 earthquake. Each fringe denotes 28 mm
 of change in range. The number of fringes
 increases from zero at the northern edge of
 the image, where no coseismic
 displacement is assumed, to at least 20,
 representing 560 mm in range difference,
 in the cores of the lobes adjacent to the
 fault. The asymmetry between the two
 sides of the fault is due to the curvature of
 the fault.
  The spatial distribution is key. Imagine being able to monitor subtle,
  aseismic ground deformation – a map of stress built-up over time.
  Locations along known faults where stress is accumulating might be
  expected to rupture before other locations where aseismic strain is not

figure not in book
New findings indicate that more than half of the right-lateral motion of the Eastern California
shear zone is sharply concentrated along the Blackwater Little Lake fault system. The rapid strain
accumulation observed along the fault system indicates that the fault is building up stress in the
shallow crust at a rate three times faster than the rate inferred from geological observations. This
may be the manifestation of stress transfer between the Garlock fault and other faults in the
Mojave area, in particular those that produced the magnitude 7.3 Landers earthquake in 1992 and
the magnitude 7.8 Owens Valley earthquake in 1872.

figure not in book
Interferometric SAR
n   Revolutionizing the study of
    earthquakes by densifying the
    spatial distribution of
    measurements, and with a high
    spatial resolution.
n   Also Used In:
    l   Glacier velocity and mass balance
    l   Groundwater withdrawal and
    l   Floodplain water storage changes
        and flow hydraulics
    l   Construction of a global high
        resolution topographic data set
    l   Atmospheric water vapor studies
    l   And more…

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