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[SSS04-P03] Complexities in Earthquake Source Spectra of the Aftershock Sequence of the 2019 Ridgecrest Earthquake
Keywords:Earthquakes, Earthquake Source Spectra, Ridgecrest
The earthquake source spectra have been modeled well by the omega-square model. However, recent studies (e.g., Denolle and Shearer, 2016; Uchide and Imanishi, 2016; Ji and Archuleta, 2020) revealed deviations in observed source spectra from the standard model. The complexity will be a window to earthquake source physics which controls the rupture complexity. Usually, the stress drops of earthquakes are calculated using the corner frequency of the omega-square model that fits the observation, and the complexity may bias the stress drop estimations.
I quantified the complexity using the multiple spectral ratio method (Uchide and Imanishi, 2016). First, I calculated spectral ratios of a single target event to many empirical Green’s function events. Then, I stacked residual spectra of the spectral ratios fitted by the omega-square model. I regarded the stacked residual spectra as the deviation from the omega-square model. I analyzed 360 events from the 2019 Ridgecrest earthquake sequence dataset provided by the Community Stress Drop Validation Study supported by the Southern California Earthquake Center (SCEC) (Baltay et al., SSA Annual Meeting 2021). As a result, I found both simple and complex events. The spatial distribution of the peak-to-peak amplitude of the stacked spectra does not show clear trends. Further investigation is needed for identifying the cause of the complexities in earthquake source spectra.
I quantified the complexity using the multiple spectral ratio method (Uchide and Imanishi, 2016). First, I calculated spectral ratios of a single target event to many empirical Green’s function events. Then, I stacked residual spectra of the spectral ratios fitted by the omega-square model. I regarded the stacked residual spectra as the deviation from the omega-square model. I analyzed 360 events from the 2019 Ridgecrest earthquake sequence dataset provided by the Community Stress Drop Validation Study supported by the Southern California Earthquake Center (SCEC) (Baltay et al., SSA Annual Meeting 2021). As a result, I found both simple and complex events. The spatial distribution of the peak-to-peak amplitude of the stacked spectra does not show clear trends. Further investigation is needed for identifying the cause of the complexities in earthquake source spectra.