SCEC Award Number 24190 View PDF
Proposal Category Individual Research Project (Single Investigator / Institution)
Proposal Title Deep seismic velocity changes as a probe of stress and damage evolution following the 2019 Ridgecrest earthquake sequence
Investigator(s)
Name Organization
William Frank Massachusetts Institute of Technology
SCEC Milestones B1-1, D1-1, D3-1 SCEC Groups Seismology, FARM, SDOT
Report Due Date 03/15/2025 Date Report Submitted 07/25/2025
Project Abstract
 Earthquakes release tectonic stress abruptly, but this stress builds slowly with time through the coupled evolution of faults and the surrounding crust. Seismic wavespeeds track crustal processes, including deformation and stress changes, but typical wavespeed monitoring methods are limited to shallow depths. Using receiver functions, we track rupture-zone wavespeed and anisotropy changes throughout the crust during the 2019 Ridgecrest earthquake sequence. Shallow co-seismic wavespeed reductions recover within months, whereas a deeper wavespeed drop accumulates post-seismically and persists without measurable recovery over several years. The deep, persistent drop in wavespeed likely reflects accumulating damage driven by post-seismic deformation, suggesting two possible scenarios: (1) a very slow inter-seismic recovery process, implying wavespeed and anisotropy track long-term stress evolution, or (2) permanent unrecoverable deformation of an immature fault zone. Both scenarios impact the dynamics and energy budget of the seismic cycle.
SCEC Community Models Used Community Stress Model (CSM)
Usage Description We used the CSM to predict how the Ridgecrest earthquakes would change the local stress state around the fault zone.
Intellectual Merit Our work has demonstrated how earthquakes impact the seismic structure and stress state throughout the fault zone of a major continental earthquake sequence. Our novel receiver function methodology captures changes in seismic wavespeeds and anisotropy that show that: (1) co-seismic damage is present in the fault zone throughout the co-seismic rupture zone; and (2) damage at depth accumulates with post-seismic deformation, and it persists throughout the post-seismic phase.
Broader Impacts The new receiver function methodology that we developed for this study is widely applicable to image and track any process that operates throughout the crust, notably at depths beyond the reach of other traditional monitoring and interferometric methods.
Project Participants Graduate student Jared Bryan led the proposed work on this project.
PI William Frank advised Bryan.
Collaborator Pascal Audet participated in scientific discussions relevant to the proposed work.
Exemplary Figure Figure 3 from relevant publication
Depth-dependent evolution of crustal seismic wavespeeds and anisotropy. (A) Time-series of the optimal transport distance for station CI.WRC2. (B) Time series of seismic wavespeed changes inverted for four depth ranges. (C) Time series of the azimuth of the fast axis of seismic anisotropy. The GNSS vertical and fault-parallel displacement rates (red lines) for station P594 are averaged in the same way as the anisotropy and are respectively shown for the pre- and post-seismic phases.
Linked Publications

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