SCEC Award Number 17098 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Deep Fault Structure Beneath the Mojave from a High Density, Passive Seismic Profile
Name Organization
Whitney Behr University of Texas at Austin Vera Schulte-Pelkum University of Colorado Boulder Thorsten Becker University of Texas at Austin
Other Participants
SCEC Priorities 3b, 3a, 1b SCEC Groups Geology, Seismology, CME
Report Due Date 06/15/2018 Date Report Submitted 06/15/2018
Project Abstract
The purpose of this project was to deploy the test phase of a high resolution, passive seismic array in the Mojave region. In May 2018, we deployed 19 broadband instruments from the new UT Austin quick deploy pool. The seismometers were deployed in a dense line, with inter-station spacing of 2-4 km over the ~40 km line; sites were chosen with permission from the Bureau of Land Management to reside on hard rock locations. The deployment spanned 1 week and was led by Robert Porritt with the help of three undergraduate students from UT Austin. The deployment is aimed at addressing two main questions that are fundamental to understanding the geologic framework and mechanical behavior of the Mojave lithosphere, including: 1) What is the distribution of ECSZ strain below the seismogenic layer in the Mojave lithosphere? And 2) How was the Mojave lithosphere modified in response to Laramide flat-slab subduction? Data gathering and analysis associated with this ‘Mojave Broadband Seismic Experiment’ will commence in the coming months, and we hope to have some initial interpretations to present at the upcoming Annual SCEC meeting in September. 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:
1) 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 models.

2) 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 1) 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.

2) The project leverages several additional sources outside of SCEC, including NSF grants award to all three PIs and UTIG funding via Becker’s startup for the seismometer pool.

3) The work being conducted is highly interdisciplinary and will facilitate broad synthesis of from a range of observations.

4) The project has already involved three UT undergraduate students who assisted with the deployment and got first hand experience in observational seismology.
Exemplary Figure Figure 1.