SCEC Award Number 14026 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Multi-scale observations of seismic anisotropy as a constraint for stress and deformation along the San Andreas Fault
Name Organization
Meghan Miller University of Southern California Thorsten Becker University of Southern California
Other Participants
SCEC Priorities 2d, 4d SCEC Groups Seismology, SDOT, USR
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
This proposal was for the collection of disparate anisotropy datasets
in order to jointly integrate them into a 3D model of anisotropy for
the southern California lithosphere, to be compared with estimates of
anisotropy from crustal stress and mantle flow models.

Our approach directly speaks to the goals of SCEC's SDOT effort.
Results will aid in constraining the 3D structure and physical state
of the lithosphere in southern California, and so to better understand
tectonic forcing and vertical force transmission. An improved model of
the anisotropic fabric of the crust, lithosphere, and uppermost mantle
will aid in building a 4D evolutionary model of the lithosphere for
all of California.

We report on highlights of results from the initial steps of our model building efforts, the comparative analysis and inspection of existing data. We discuss shear zones in light of SKS splitting as well as shallow and deeper crustal alignment of different indicators of deformation from seismicity, geodesy, and noise surface wave tomography.
Intellectual Merit The structural model that we envision to build could serve several
SDOT objectives. In particular, it could form the backdrop against
which to evaluate shallow, crustal shear-wave splitting as a possible
constraint for validation of the Community Stress Model (CSM), as
solicited in the 2014 RFP by means of "compilations of diverse stress
constraints (e.g.\ from borehole or anisotropy measurements)".
Broader Impacts A better understanding of crustal rheology and stress.
Exemplary Figure Figure 2: Left: Comparison of coseismic “stress” from Michael (1984) type inversion (green, from
Yang and Hauksson, 2013) and Kostrov summed strain-rates (yellow) based on the same focal
mechanisms (Yang et al., 2012) (compressive axes show). Right: angular difference, Da, between
the two axes, with sign determined as indicated in the legend, along with histogram (y axis showing
frequency percent) over all sampled regions (sub plot), with legend stating the mean ± standard
deviation of Da.