SCEC Award Number 22118 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title CONTINUATION: UCSB BROADBAND KINEMATIC RUPTURE SIMULATION WITH A DOUBLE CORNER SOURCE SPECTRUM
Investigator(s)
Name Organization
Ralph Archuleta University of California, Santa Barbara Chen Ji University of California, Santa Barbara
Other Participants
SCEC Priorities 4c, 4b, 4a SCEC Groups GM, Seismology, FARM
Report Due Date 03/15/2023 Date Report Submitted 11/15/2024
Project Abstract
 We studied the earthquake source spectral characteristics to improve ground motion prediction. In the UCSB method, a source spectrum needs to be specified to constrain the source realizations. Initially, a single corner (SCF) spectrum was assumed, with the seismic moment〖 M〗_0 and “stress parameter” 〖Δσ〗_B as global parameters. Our review of theoretical source spectral models showed that, despite the variation in predicting static stress drop 〖Δσ〗_s from M_0 and corner frequency f_c, all models suggest that earthquakes radiate about half of the available strain energy into the medium (Ji et al., 2022). This supports a less model-dependent approach to estimate 〖Δσ〗_s, though the estimates rely on apparent seismic radiation efficiency (=2 σ_a⁄〖Δσ〗_s , σ_a is apparent stress). Modeling PGA and PGV of the NGA West-2 database, we introduce double-corner-frequency (DCF) source spectral models JA19 and JA19_2S for 3.3 6) earthquakes.
Intellectual Merit The earthquake source spectra count important information about earthquake rupture. The intellectual merits of our works include a) two DCF source spectral models JA19 and JA19_2S that explain the observed PGAs and PGVs of NGA West-2 data. (b) source physical interpretation of non-self-similarity relationships of the JA19_2S. (c) A new and more efficient way to characterize earthquake source spectrum. (d) The depth dependence of 〖Δσ〗_B and σ_a.
Broader Impacts A critical need for earthquake engineering is knowledge of near-source ground motion from damaging crustal earthquakes. While the data are becoming more plentiful (e.g., Ancheta et al., 2014), there is a notable lack of data within 20 km of the causative fault for earthquakes with M>6. Physics-based kinematic earthquake scenarios can provide computed broadband accelerograms for a wide range of magnitudes and distances.
Exemplary Figure Figure 2
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