SCEC Award Number 13030 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Finite-Source Modeling and Stress Drop Estimate of Anza Microearthquakes: Implication for Fault Strength and Earthquake Nucleation
Investigator(s)
Name Organization
Taka'aki Taira University of California, Berkeley
Other Participants
SCEC Priorities 1, 4, 2 SCEC Groups Seismology, FARM, CME
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 We investigate the spatial extent of rupture and stress drop for the 2013 Mw 4.7 Anza earthquake using a finite-source rupture inversion with an empirical Green’s function approach. We find a strong directivity of rupture propagation in the northwest direction. Our sensitivity analyses suggest that the rupture velocity is near the shear wave velocity and the rise time is short (~0.03 sec). The slip distribution from the finite-source inversion shows a very high peak and average slips, in exceedance of 50 cm and 10 cm respectively. The resultant peak and average stress drops are about 70 MPa and 20 MP.
Intellectual Merit We determined the spatial distribution of earthquake stress drop within the rupture interior of the 2013 Mw 4.7 Anza earthquake. Our result shows the heterogeneity of stress drops including the two asperities in which the maximum stress drops are about 60 MPa. An implication of our work is that there are locally high levels of fault strength on the San Jacinto fault.
Broader Impacts The project enabled the education and training of a female graduate student, Katie Wooddell at UC Berkeley.
Exemplary Figure Figure 4: Preferred slip model and MRF comparisons with synthetic solutions for eGF8 using the parameters listed in Table 2. The hypocenter is shown with a white square.