SCEC Award Number 20156 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Distinguishing off-fault strain rates from on-fault elastic coupling using geostatistics and elastic models
Investigator(s)
Name Organization
Jeremy Maurer Missouri University of Science and Technology Kaj Johnson Indiana University
Other Participants 1 Graduate Student, Missouri S&T
1 Graduate Student, Indiana University
SCEC Priorities 2a, 3e, 1a SCEC Groups Geodesy, SDOT, Geology
Report Due Date 03/15/2021 Date Report Submitted 07/09/2021
Project Abstract
 In this work we present preliminary results from using geostatistics and body-force methods to com-pute surface strain rate from geodetic data. These methods allow us to quantify the uncertainty in strain rate for a given method and compare to the uncertainty arising due to differences between methods. We furthermore have developed a methodology for estimating backslip rates on faults from surface strain rate directly, which allows to differentiate between strain that may be accruing elastical-ly through fault coupling and strain that cannot be accounted for in this way. Our preliminary results for southern California show high strain rate along the San Andreas Fault, as expected, and relatively low uncertainty (peak uncertainty <25% peak strain rate) for the geostatistical method. Uncertainty is low in locations with data, as expected. Total moment accumulation rate has a fairly low uncertainty (+/- 3%).
Intellectual Merit We have developed methodology for rigorously characterize uncertainty in surface strain rates estimated using geodetic data, and also a method for directly using surface strain rates to solve for backslip on faults. We have applied the results to California and obtained a distribution of strain rates and total moment accumulation rates that can be used to inform seismic hazard models.
Broader Impacts This project has supported a graduate student working with PI Maurer on estimating surface strain rates. In addition, the project itself is addressing uncertainty quantification of strain rate, which is related to earthquake hazard. Improved understanding of uncertainty in the strain rates and how it propagates through to elastic fault coupling will improve understanding of earthquake hazard in California and allow for better decisions that can account for uncertainty in the estimated fault slip deficit rates.
Exemplary Figure Figure 2. Illustration of strain rate inversion method for backslip on faults. J2 is the second strain-rate invariant. The observed strain rate field is computed using the body-force method. J2 predicted is the strain rate attributed to elastic coupling along faults. Residual J2 is strain rate attributed to off-fault deformation processes.