Comparing Finite-Source and Corner Frequency Based Stress Drop for the Ridgecrest Sequence
Abstract
We seek better understanding of the relationship between finite-source model and corner frequency based estimates of stress drop, and the variability and uncertainty in stress drop estimates. In this study we apply finite-source and corner frequency source estimation methods to the Ridgecrest sequence earthquakes compiled for the Community Stress Drop Validation Study lead by Baltay and Abercrombie. For events where it is possible we determine kinematic finite-source models by inverting seismic moment rate functions from empirical Greens function deconvolution, and then use the resulting slip models to estimate the coseismic stress change (Ripperger and Mai, 2004), and the peak and average stress drop. We measure corner frequencies using the method of Malagnini et al. (2020). The corner frequencies are used to determine stress drops using the available mechanical models relating rupture area, slip and stress drop to corner frequency. We compare these estimates with the finite-source results in the context of the uncertainties for both the corner frequency and finite-source estimates. Our previous work (Malagnini et al., 2020) found that finite-source mean stress drop correlated best with the Brune stress drop from corner frequency estimates for the 1994 Northridge, California and the 2008 Wells, Nevada earthquakes. Preliminary work for Ridgecrest aftershocks shows corner frequency estimates within 1-10 MPa with a slight non-self-similar trend toward lower stress drop with deceasing moment. We have developed finite-source models for 5 moderate (Mw 4.5-5.5) aftershocks and find average stress drop ranging from 1.3 to 22 MPa. We are in the processing of compiling results for more events and evaluating uncertainties in the source models and propagating that uncertainty to stress drop.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.S45A0288D