SCEC Award Number 24057 View PDF
Proposal Category Individual Research Project (Single Investigator / Institution)
Proposal Title Kinematic models for statewide California
Investigator(s)
Name Organization
Sylvain Barbot University of Southern California Mingqi Liu University of Southern California
SCEC Milestones A1-3, D1-1 SCEC Groups Geodesy, PBS, SDOT
Report Due Date 03/15/2025 Date Report Submitted 03/18/2025
Project Abstract
 Although geological and geodetic observations provide a good estimate of the surface deformation of the California margin, the pattern of flow beneath the lithosphere remains poorly constrained. Plastic flow in the lower crust and upper mantle entrains the rocks of the brittle layer by elastic coupling. Geodetic measurements in the inter-seismic period can be used to illuminate the distribution of strain in the ductile regions, compatible with the rheological structure of the lithosphere. Inversion of the Plate Boundary Observatory (PBO) velocity field reveals the broad pattern of horizontal flow beneath California. We improved the resolution of the plastic flow underneath California by augmenting the PBO data with velocity measurements from the Median Interannual Difference Adjusted for Skewness (MIDAS) data product and from a spatially extensive stack of Advanced Land Observing Satellite (ALOS) PALSAR synthetic aperture radar interferograms. We assessed how the combination of these data improves the vertical and horizontal resolution of plastic flow at the subduction zone interface and the transition to the tectonic regime of the Basin and Range to the east. We reconstruct the subsurface strain-rate distribution by inversion of the Plate Boundary Observatory (PBO) velocity field, the Median Interannual Difference Adjusted for Skewness (MIDAS) data product (Blewitt et al., 2016), and Advanced Land Observing Satellite (ALOS) PALSAR synthetic aperture radar interferograms (Tong et al., 2013). MIDAS provides 697 continuous, campaign, and semi-continuous GNSS measurements in the study area. ALOS provides 53,793 line-of-sight measurements at near and intermediate distances from the trace of the San Andreas Fault.
SCEC Community Models Used Community Geodetic Model (CGM)
Usage Description We use the Community Geodetic Model (CGM) to constrain the kinematics of lower-crustal faults and deep mantle flow underneath the California margin.
Intellectual Merit The proposal improves our understanding of the boundary conditions driving fault activity in California. The project provides the stress-rate impose on the seismogenic zones of active faults. The products of this proposal can be used to constrain the recurrent time of earthquakes.
Broader Impacts The proposal supported the creation of new teaching material at the Department of Earth Sciences of the University of Southern California. Content from the proposal was incorporated into the graduate level class GEOL558: Inverse Theory in the Earth Sciences. The new teaching material provides examples and tutorials for students to analyze geodetic data.
Project Participants The project involved the postdoctoral fellow Dr. Mingqi Liu at the University of Southern California.
Exemplary Figure Figure 2. Contribution of viscoelastic flow on plate boundary deformation. The background color indicates the spatial distribution of strain accumulation along the plate boundary. The pairs of black arrows indicate the principal axes of the strain-rate tensor. The white arrows indicate the surface velocity predicted by the model. The dashed black lines with arrows are the flow streamlines. The thick red lines indicate the major strike-slip faults. The red stars and black circles show the hypocenter of historical earthquakes and earthquakes from moment magnitude 3 and above from 1990 to 2020 around California, respectively.
Linked Publications

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