SCEC Award Number 19096 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Interpreting crustal and lithospheric structure in the Eastern California Shear Zone underneath the Mojave Broadband Array
Name Organization
Thorsten Becker University of Texas at Austin Vera Schulte-Pelkum University of Colorado, Boulder
Other Participants Wanying Yang
SCEC Priorities 3b, 3a, 3g SCEC Groups Seismology, FARM, SDOT
Report Due Date 04/30/2020 Date Report Submitted 04/30/2020
Project Abstract
The project supported analysis of data from a high resolution, passive seismic array in the Mojave region. In May 2018, we deployed 19 broadband seismometers from the UT Austin UTIG quick deploy pool. The seismometers were deployed in a dense line, with interstation spacing of 2-4 km over the ~40 km line. The experiment is aimed at addressing two main questions: 1) What is the distribution of Eastern California Shear Zone strain below the seismogenic layer in the Mojave lithosphere, and how does this structure compare to more mature faults? And 2) How was the Mojave lithosphere modified in response to Laramide flat-slab subduction?
Stations were serviced and data retrieved in October 2019. We conducted teleseismic shear wave splitting and receiver function analysis, and initial results were presented at the 2019 September annual SCEC meeting. The results of this project will be used to evaluate fault loading beneath the Eastern California Shear Zone, and to help populate and test models of lithospheric structure and anisotropy for use in the SCEC Community Rheology, Velocity, and Stress Models.

Intellectual Merit The Intellectual Merit associated with this project includes:
Better imaging of the deep fault structure and distribution of strain (localized vs. distributed) beneath the Eastern California Shear Zone, with implications for basal loading of upper crustal faults, postseismic relaxation, and earthquake cycle as well as fault evolution models.
Improved understanding of the Laramide lithospheric modification in the Mojave mantle lithosphere, including determining the composition of the lower crust (schist or no schist), the role of duplexing in the mantle lithosphere, and the hydration state of the lower crust and upper mantle, with implications (as above) for fault loading, postseismic relaxation, and earthquake cycle models.

Broader Impacts Broader impacts include the following:
The high resolution seismic line focused on the Mojave region is complementary to efforts associated with developing the SCEC Community Rheology Model, particularly since the CRM community has identified the Mojave region as the ideal locality for implementing an initial version of the CRM.
The project leverages several additional sources outside of SCEC, including NSF grants awarded to all three PIs and UTIG funding via Becker’s startup for the seismometer pool.
The work being conducted is highly interdisciplinary and will facilitate broad synthesis of a range of observations.
The project has already involved three UT undergraduate and three graduate students who assisted with the deployment and gained first hand experience in observational seismology.

Exemplary Figure Figure 1: Common Conversion Point stacks of radial receiver functions using UT Austin’s Mojave Broadband Array data from first (top) and second (bottom) service run. No smoothing is applied. The additional year of data filled in gaps seen in the early plot.