SCEC Award Number 12005 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Reexamining the effects of material heterogeneity on the slip distribution of the 1994 Northridge earthquake
Investigator(s)
Name Organization
John Loveless Massachusetts Institute of Technology Brendan Meade Harvard University Carl Tape University of Alaska, Fairbanks
Other Participants One (1) Smith College undergraduate
SCEC Priorities 4a, 1d, 4c SCEC Groups Geodesy, USR, CS
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 The major goal of this ongoing research is to build a modeling framework integrating three-dimensional heterogeneity in material properties that may be used to interpret quasi-static geodetic observations of earthquake cycle deformation. We first estimated coseismic slip distributions on a Community Fault Model-based, non-planar representation of the Northridge source fault within a homogeneous elastic half-space and layered elastic space but found that neither model provides a satisfactory fit to the data. We used an adaptive fault remeshing routine to find element sizes and smoothing constraints that are appropriate for the data distribution and modeling framework. In developing the framework for assessing the impact of 3D crustal structure on the slip distribution estimate, we generated an initial catalog of Green’s functions based on the static offsets predicted by SPECFEM3D simulations of earthquake sources located on the Northridge source fault.
Intellectual Merit Our overarching goal is a publicly available catalog of Green’s functions generated with SPECFEM3D that integrates several SCEC initiatives. The Community Fault Model will serve as the source geometry on which interseismic slip deficit and coseismic slip occur. Seismic wave propagation through the crust with properties as represented in the Community Velocity Model is simulated using SPECFEM3D. Static displacements due to unit slip on CFM sources are predicted at GPS stations of the Community Motion Model, providing a full suite of Green’s functions to be used by the crustal deformation modeling community. We envision this product being made available first for the Northridge source fault, our test case, but eventually for all structures within the CFM, allowing the Green’s functions to be implemented in estimating the distribution coseismic slip of future earthquakes and of ongoing earthquake cycle processes throughout southern California.
Broader Impacts This project funded a summer research fellowship for Bismita Sahu, a current Smith College junior engineering major. The research gave her experience in Matlab programming, inverse theory, and earth science, allowing her to see connections between her engineering coursework and a natural application.
Exemplary Figure Figure 4. Moment tensors equivalent to unit strike (left) and dip (right) slip at the centroids of the 58 elements representing the Northridge source fault. Each earthquake source is used as input into SPECFEM3D, giving the catalog of Green’s functions relating fault slip to surface displacement via wave propagation through the CVM-H. Figure prepared by Carl Tape.