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Report | SCEC Research Accomplishments
System (from the SCEC
Geological Vertical Motion
Map). Their models are
driven by applied basal
forces, and they incorporate
layered viscoelasticity and
realistic geometries to model
the deformation of the SAFS
over the past million years (a
schematic is shown on
Figure 42). The crust is either
treated as fault-bounded
elastic blocks, or as an
elastic-plastic continuum, in
which faults are allowed to
develop in response to
imposed velocities at the
edges of the model (so far,
the former approach works
best). Comparisons show horizontal strain rates and long-term uplift rates that are broadly consistent with observations
(Figure 43). The models developed to date are a preliminary step towards a more complete model of the long-term
development of the western North American plate boundary over the last 10 Ma.
Figure 43. Color contour plots of A) semi-analytical (Smith-Konter and Sandwell, 2009) and B) dynamically modeled
strain rate (nanoStrain/yr) of the San Andreas Fault System. Color scale is saturated at 500 nanoStrain/yr. Black lines
indicate the location of major faults for spatial reference. Coastlines are shown in white. From Benjamin Hooks.
72 | Southern California Earthquake Center
Figure 42. Schematic showing the geometry, applied basal kinematic driving force, rheological
stratification, and boundary conditions for Benjamin Hooks' regional-scale, long-term deformation model.
The model encompasses an area of 750 km by 750 km centered on southern California. A relative velocity
of 45 mm/yr across the model is assumed. The model incorporates a pressure-dependent upper crust
rheology (coefficient of friction angle of = 35° with strain-softening conditions), and a plastic-yield lower
crust rheology (based upon published flow laws, e.g. Mackwell et al., 1998). From Benjamin Hooks.