FlatMaxwell_topoStress_HiResIso0p50.dat
is the FlatMaxwell "topographic stress" model with the following characteristics:
*HiRes = high-resolution grid of points with spacing of 10 km horizontally and 1.25 km vertically.
*Uses the isostatic Moho option (instead of the seismic Moho option), because this yields a
slightly better fit to data, and because it predicts less shear stress in the asthenosphere.
*Uses effective Poisson ratio of 0.50 to represent the mature stages of viscoelastic relaxation
after millions of years of topographic loading. (Poisson ratio of 0.25 represents only the
initial response to new loading.)
Note that this is NOT a complete model of the stress field in southern California, because it
lacks any tectonic stress component.
This topographic-stress model was a component of each of the following two full solutions:
FlatMaxwell_tectoStress_HiRes043.dat
is the FlatMaxwell "tectonic stress" solution that (together with the topographic stress model above)
makes up "Version: HiRes043" of the "FlatMaxwell" model that was posted on the SCEC CSM 2015.03.20.
It was computed using the following parameter values: mode = 2, waves = 6, sigma_factor = 0.05,
data_weight = 0.50, damper = 1.0D-7. In this model, the use of a positive sigma_factor led to
improved values of 9-out-of-10 misfit measures, and reduced the unphysical "ringing" of stress
anomalies in the deeper parts of the model. Hence, it appeared to be the best. However, later
it was noted that this model has a consistent tendency to under-fit the shear-stress targets
coming from the Shells model. (See 4_graphics\59011_... and 59012_... which illustrate this.)
FlatMaxwell_tectoStress_HiRes045.dat
is the FlatMaxwell "tectonic stress" solution that (together with the topographic stress model above)
makes up an alternate "FlatMaxwell" model that was created for the SCEC CSM Workshop 2015.09.13..
It was computed using the following parameter values: mode = 2, waves = 6, sigma_factor = 0.00,
data_weight = 0.50, damper = 1.0D-8. In this model, the use of zero for sigma_factor led to slightly
higher values of 9-out-of-10 misfit measures, and slightly more unphysical "ringing" of stress
anomalies in the deeper parts of the model. However, it does a better job of approximating the
shear-stress target values coming from the Shells model. (See 4_graphics\61011_... and 61012_...
which illustrate this.) Thus, this could be considered an alternative model.
Peter Bird
Department of Earth, Planetary, and Space Sciences
UCLA
pbird@epss.ucla.edu
2015.09.23