Characteristics of earthquake source complexity in the San Jacinto Fault Zone

Qimin Wu, & Xiaowei Chen

Published August 15, 2018, SCEC Contribution #8653, 2018 SCEC Annual Meeting Poster #077

We systematically analyze the source complexity of earthquakes in the trifurcation area of the San Jacinto Fault zone (SJFZ), which represents a right-lateral strike-slip system that is of high structural and geometric complexity and most seismically active in southern California. We combine both frequency and time domain analysis based on the empirical Green’s function (EGF) technique to investigate the characteristics of source complexity for earthquakes with a range of magnitudes (~M 2.5-5) to better understand the underlying earthquake physics and the associated seismic hazard of these earthquakes. In time domain, we apply an iterative deconvolution method to retrieve relative source time functions (RSTFs) for our target events using smaller nearby events as EGFs. The RSTFs obtained from multiple EGFs are stacked at each station to stabilize the results by removing random noise. Preliminary results for moderate earthquakes (~M 4-5) reveal clear directivity effects and the existence of multiple subevents. In frequency domain, we apply the multiple spectral ratio method (e.g., Uchide and Imanishi, 2016; Abercrombie et al., 2017), in which various EGF events are used to obtain spectral ratios for our target events. We explore the complexity of the stacked spectral ratios by examining their azimuthal variations and quantifying their deviation from simple omega-square source model. Preliminary results demonstrate that the spectral ratios of some events as small as ~M 3 deviate significantly from the simple omega-square source model. Further analysis will combine the time and frequency domain results to identify any dependence of apparent source complexity on magnitude or structural complexity.

Key Words
source complexity, source time function, EGF method

Citation
Wu, Q., & Chen, X. (2018, 08). Characteristics of earthquake source complexity in the San Jacinto Fault Zone. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology