San Andreas Elastic Deformation Model
Coulomb Stress Accumulation along the San Andreas Fault
System
Bridget
Smith and David Sandwell
J. Geophys. Res., 2003
Stress
accumulation
rates along the primary segments of the San Andreas Fault system are
computed
using a
3D
elastic halfspace model with
realistic fault
geometry. The model is developed in the Fourier domain by solving for
the
response of an elastic halfspace due to a point vector body force and
analytically integrating the force from a locking depth to infinite
depth. This approach is then applied to the
San Andreas Fault system using published slip rates along 18 major
fault
strands of the fault zone.GPSderived horizontal velocity measurements
spanning then entire 1700 x
200 km region are then used to solve for apparent locking depth along
each
primary fault segment.
This simple
model fits remarkably well (2.43 mm/yr rms misfit), although some
discrepancies
occur in the Eastern California Shear Zone.The model also predicts
vertical uplift and subsidence
rates that are in agreement with independent geologic and geodetic
estimates. In addition, shear and normal stress
along the major fault strands are used to compute Coulomb stress
accumulation
rate. As a result, we find earthquake recurrence intervals along the
San
Andreas Fault system to be inversely proportional to Coulomb stress
accumulation rate, in agreement with typical coseismic stress drops of
110
MPa.This 3D deformation model
can ultimately be extended to include both timedependent forcing and
viscoelastic response.
In
addition, shear and
normal stresses along the major fault streands are used to compute
Coulomb stress
accumulation rate. As a ersult, we find earthquake recurrence intervals
along the San
Andreas Fault system to be inversely proportional to Coulomb stress
accumulation rate,
in agreement with typical coseismic stress drops of 110 MPa. This 3D
deformation
model can ultimately be extendend to include timedependent forcing and
viscoelastic
response.
