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Assessing the Accuracy of Earthquake Stress Drop Estimation Methods for Complex Ruptures Using Synthetic Earthquakes

Description: 

We evaluate how well simple, commonly used stress drop estimation methods are able to recover the known stress drop of synthetic, complex ruptures, constructed by combining multiple simple kinematic source models. Earthquake stress drop is a commonly estimated parameter that can provide insight into both earthquake source physics and the resulting ground motion. Stress drop methods usually assume that earthquakes are a symmetric circular crack which release their energy in a single pulse with a simple, symmetric source time function (STF). Real earthquakes, however, often have complex source time functions with multiple pulses of seismic moment release. Because recent studies have shown that stress drop estimates contain significant uncertainties, and independent analyses of the same earthquakes often produce conflicting estimates, we seek to identify how different methods perform on the known, synthetic, complex events.

In this study, we create a synthetic catalog of complex rupture earthquakes by combining multiple simple, circular-crack spectral models to create complex STFs with known static stress drops. We then apply time-domain methods (i.e., rupture duration) and frequency-domain methods (such as corner frequency) to estimate stress drop. Our results suggest that the frequency-domain method performs better than the time-domain method when applied to complex earthquakes. However, frequency-domain stress drop estimates more strongly correlate with the stress drop of the largest moment pulse rather than the average stress drop of the entire rupture area. Identifying which stress drop estimation methods (or combination of methods) perform best under which circumstances will allow us to reassess prior stress drop studies to determine whether observations reflect real tectonic trends or are simply artifacts of the methodology. This analysis will help lead to new insights into earthquake source processes and more accurate assessments of future earthquake hazards.

Session: Understanding the Variability in Earthquake Stress Drop Measurements

Type: Oral

Date: 4/20/2023

Presentation Time: 02:45 PM (local time)

Presenting Author: James S. Neely

Student Presenter: No

Invited Presentation: Yes

Authors