SCEC Award Number 20073 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Aftershocks of the Ridgecrest Earthquake Sequence and Their Relationship to Mainshock Slip and Scaling of Source Parameters
Investigator(s)
Name Organization
Taka'aki Taira University of California, Berkeley Sierra Boyd University of California, Berkeley Douglas Dreger University of California, Berkeley
Other Participants
SCEC Priorities 1d, 1e, 1c SCEC Groups CXM, SDOT, Seismology
Report Due Date 03/15/2021 Date Report Submitted 03/14/2024
Project Abstract
 The connection between the strength of tectonic faults and the earthquake rupture is central to studies of the physics of earthquakes. Earthquake stress drop is one of source parameters for the earthquake rupture process that can be obtained from observed waveforms. We used empirical Green’s functions, waveforms of nearly collocated smaller events, to correct for path, site and common elements in the source (focal mechanism) and recover an estimate of the seismic moment rate function (MRF). We comprehensively searched for possible eGf events for target earthquakes (with magnitude greater than 4.0) that occurred within 100km from the 2019 M7.1 Ridgecrest rupture area during the 2019-2020 period. A total of 148 earthquakes were analyzed as the target earthquakes. We performed the deconvolution separately for each component and then stacked the three-component MRFs at each station to enhance signal-to-noise ratios (SNRs). We evaluated the quality of resultant MRFs based on resultant SNRs (Figure 1). If more than 10 stations exhibit their SNR higher than 15, we consider this eGf-target event pair for the finite-fault modeling. The first event analyzed occurred on July 6, 2019 at 04:18:55 UTC in the northern part of the aftershock zone (Figure 2) of M 5.4 and our analysis finds an average stress drop of 20.7 MPa.
Intellectual Merit We searched for possible empirical Green’s function earthquake for the 148 Ridgecrest earthquake (M>=4) and performed the finite-fault modeling. This project advances our understanding of the rupture processes of the Ridgecrest earthquake sequences.
Broader Impacts This project supported the intellectual development of an undergraduate student Jose Magana. The student was supported to present his work at the 2020 SCEC, 2020 AGU, and 2021 SSA meeting. The results from this project are summarized in his senior thesis.
Exemplary Figure Figure 3. Spatial distributions of A) fault slip and B) stress drop for the 2019 Mw 5.44 Ridgecrest earthquake.