Review of Submitted CSM Models Jeanne Hardebeck!
USGS, Menlo Park, CA!
Community Stress Model (CSM) strategy:!
!
•  Long-term goal: a model or set of models of stress and stressing rate
in the southern California lithosphere.!
•  First step (ongoing) is to collect existing stress and stressing rate
models from the SCEC community. !
•  Plan to construct the final CSM model by combining the models and/
or using them to form branches. !
•  Differences between contributed models:!
1.  Reconcile through further work.!
2.  Consider their variation to represent the uncertainty. !
3.  Choose a preferred model, or relative weighting of models.!
4.  Become CSM model branches.!
Model Format:!
!
Spatial sampling:!
-  All models sampled on a common grid: covers San Andreas from creeping section to Gulf
of California, state border on the east to continental borderland on the west. !
-  2 km spacing at 1 km to 25 km depth, 5 km spacing at 50, 75, and 100 km depth.!
-  Should oversample models (no aliasing).!
-  Modelers are responsible for any necessary interpolation of their models.!
Model Format:!
!
Spatial sampling:!
-  All models sampled on a common grid: covers San Andreas from creeping section to Gulf
of California, state border on the east to continental borderland on the west. !
-  2 km spacing at 1 km to 25 km depth, 5 km spacing at 50, 75, and 100 km depth.!
-  Should oversample models (no aliasing).!
-  Modelers are responsible for any necessary interpolation of their models.!
Stress field representation: !
-  Stress or stressing rate (MPa or MPa/yr).!
-  Representation options: Stress tensor, or SHmax direction and SHmax, Shmin, and SV
stress magnitudes.!
-  Almost all contributed models are represented as stress tensors, although not all models
have meaningful isotropic and/or deviatoric stress amplitudes.!
-  Model uncertainty was requested, but almost no submitted models included uncertainty
estimates.!
Contributed Stress Models:!
!
1)  Inversion of focal mechanisms for stress orientation. – Wenzheng Yang and
Egill Hauksson (Caltech). [Similar model by Hardebeck (USGS), not used as
to not double-weight focal mechanism inversions.]!
!
2)  SHELLS finite element model including topography, depth-dependent
rheology, frictional faults, and long-term deformation model. – Peter Bird
(UCLA).!
!
3)  Inversion for stress field that fits topography, fault loading from dislocation
model, tectonic loading, and focal mechanisms. – Karen Luttrell (USGS),
Bridget Smith-Konter (Texas), and David Sandwell (UC San Diego).!
4)  Smoothing of World Stress Map (SHmax direction only). – Peter Bird (UCLA);
Jeanne Hardebeck (USGS).!
5)  Global model from density-driven mantle flow, plus lithosphere gravitational
potential energy, fit to geoid and global plate motions. – Attreyee Ghosh
(Bangalore Inst. Tech.) and Thorsten Becker (USC).!
Yang & Hauksson!
phi=(σ2-σ3)/(σ1-σ3)!
Aphi=phi 0-1 : normal faulting (σ1 most vertical)!
Aphi=2-phi 1-2 : strike-slip faulting (σ2 most vertical)!
Aphi=2+phi 2-3 : reverse faulting (σ3 most vertical)!
Bird SHELLS!
phi=(σ2-σ3)/(σ1-σ3)!
Aphi=phi 0-1 : normal faulting (σ1 most vertical)!
Aphi=2-phi 1-2 : strike-slip faulting (σ2 most vertical)!
Aphi=2+phi 2-3 : reverse faulting (σ3 most vertical)!
Luttrell, Smith-Konter & Sandwell!
phi=(σ2-σ3)/(σ1-σ3)!
Aphi=phi 0-1 : normal faulting (σ1 most vertical)!
Aphi=2-phi 1-2 : strike-slip faulting (σ2 most vertical)!
Aphi=2+phi 2-3 : reverse faulting (σ3 most vertical)!
Bird WSM!
Hardebeck WSM!
Ghosh & Becker!
phi=(σ2-σ3)/(σ1-σ3)
Aphi=phi
0-1 : normal faulting (σ1 most vertical)
Aphi=2-phi 1-2 : strike-slip faulting (σ2 most vertical)
Aphi=2+phi 2-3 : reverse faulting (σ3 most vertical)
Stress Models: differen/al stress (σ1-­‐σ3) versus depth. Solid line/symbol: median. Dashed line: middle 68%. Contributed Stressing Rate Models:!
!
!
1)  Block model fit to geodetic data. – Jack Loveless (Smith) and
Brendan Meade (Harvard).!
!
2)  Fault loading from dislocation model using geologic and geodetic
slip rates. – Bridget Smith-Konter (Texas), and David Sandwell
(UC San Diego).!
3)  Fault loading from dislocation model plus static stress changes
from earthquakes. – Anne Strader and David Jackson (UCLA).!
4)  Local boundary element model fit to slip rates (LA, Ventura, San
Gregorio). – Michele Cooke (UMass) and Scott Marshall
(Appalachian State).!
Loveless & Meade!
Smith-Konter & Sandwell!
Strader & Jackson!
Cooke!
Marshall LA!
Marshall Ventura!
More information about each model is available in
the modelersʼ talks from the 2012 CSM workshop:!
!
http://www.scec.org/workshops/2012/csm/index.html!