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Space-Time Variations in Earthquake Waveform Similarity: Implications for Stress Heterogeneity and Faulting Complexity

Session: Waveform Cross-Correlation-Based Methods in Observational Seismology I

Type: Oral

Date: 4/21/2021

Presentation Time: 02:00 PM Pacific

Description: 

Cross-correlation methods can provide a measure of the waveform similarity of nearby earthquakes. Similar earthquake pairs have been extensively studied for the application of hypocentral relocation methods or for analyses of repeating earthquakes. In these contexts, waveform similarity is often a binary definition: either an earthquake pair is similar or it is not. In reality, earthquake similarity exists on a continuous spectrum from highly similar to highly dissimilar. When viewed in this way, waveform similarity can be used as a tool to gain insight into heterogeneity in the stress field and local fault network over short length scales (< 1km). In this work, we characterize waveform similarity for a dataset of tens of thousands earthquakes near Ridgecrest, California, focusing in particular on resolving changes in similarity in space and in time. To do this, we combine a high-precision relocated catalog with the cross-correlation of full waveforms across multiple stations to measure how similar each earthquake is to its nearest neighbors. The occurrence of the July 2019 Ridgecrest mainshocks causes a sharp and persistent reduction in waveform similarity throughout the region, implying complexity in the stress field and activated faults on length scales of hundreds of meters or less. Among the Ridgecrest aftershocks, we observe coherent variations of waveform similarity along the rupture trace of the M7.1 mainshock. We also find a selection of anti-similar aftershock pairs, which have waveforms that are nearly identical at multiple stations except with reversed polarity. Taken together, these methods and observations lay the foundation for new approaches into understanding faulting and stress heterogeneity during complex earthquake sequences.

Presenting Author: Daniel T. Trugman

Student Presenter: No

Authors