Annual Meeting - SCEC.org

Poster Abstracts | Group 1 – CDM
Crustal Deformation Modeling (CDM)
1-097
DETAILED SEISMIC AND TECTONIC MOMENT RATE DISTRIBUTION IN
CALIFORNIA AND THE GREAT BASIN Kreemer C, Torres R, Zaliapin I, Pancha A, and
Anderson JG
Regional earthquake occurrence rate and seismic moment rate estimates are an integral part of any
physics-based seismic hazard assessment. Ultimately, one would want to be able to connect the
moment rate from the observed seismicity to its long-term predictions based on geodetic and
geological information. Previous statistical research, theoretical and numerical, has found that
geodetic and geological information can improve significantly the catalog-based estimations of the
moment rate and earthquake occurrence models. In this study we compared a most detailed
geodesy- and geology-based expected moment release with the observed one on different temporal
and spatial scales in California and the Great Basin. We have analyzed GPS data from all
continuous sites in California and the Great Basin and combined the resulting horizontal velocities
with those from published campaign-style studies. A high-resolution continuous strain rate tensor
model is derived from an interpolation of those geodetic velocities. Additional constraints on the
style, rate, and localization of strain are incorporated from Quaternary faults used in the 2002
Seismic Hazard Map. The strain rate model is characterized by having both the highest strain rates
narrowly concentrated along major faults as well as lower strain rates heterogeneously distributed
over the remaining plate boundary. Strain rates are converted to long-term, or tectonic, moment
rate estimates for sub-regions of varying size. This tectonic moment rate is then compared with the
observed earthquake occurrence rate and seismic moment release. The comparison with the
observed moment rate clearly demonstrates a well-documented moment deficiency that arises due
to the combination of the heavy-tailed distribution of seismic moment and the typically short timespan
of catalogs. Our results expand the previously established spatio-temporal bounds of the
statistical modeling framework for the seismic moment release from hundreds of years and
thousands of kilometers down to years and tens of kilometers.
1-098
EFFECTS OF 3-D VARIATIONS IN FAULT GEOMETRY AND ELASTIC STRUCTURE
ON GEODETIC VELOCITIES, VENTURA BASIN REGION, CALIFORNIA Lu J, Gable
CW, Williams CA, and Hager BH
Geodetic observations of interseismic elastic strain accumulation and coseismic strain release are
sensitive to the heterogeneous rheology of the lithosphere. Even though models assuming simple
rheology might fit observed geodetic velocities well, conclusions about fault behavior could be
biased if lateral and vertical variations of the lithosphere's mechanical properties are not accounted
for. We are developing 3-D Crustal Deformation Models (CDM) of southern California using the
Finite Element Method (FEM), accounting for realistic fault geometries provided by the SCEC
Community Fault Model (CFM) and 3-D variable elastic properties provided by the SCEC
Community Velocity Models (CVM). We are using the mesh generation package LaGriT to create
the meshes. To perform the modeling itself, we are using PyLith. The model we present here
encompasses the region around the Ventura Basin, including the San Cayetano, Oak Ridge and
Santa Susana faults.
We perform three different calculations of coseismic displacements of the Ventura Basin model: 1)
analytic models using the rectangular dislocation based (CFM-R) fault geometry assuming
homogeneous elastic properties; 2) FEM models using our meshing of the T-surf based CFM
assuming homogeneous elastic properties; 3) FEM models using our meshing of the CFM including
122 | Southern California Earthquake Center