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Novel Location Method for ETS Tremor in Northern Cascadia

Episodic tremor and slip (ETS) in Cascadia is characterized by a transient reversal of long-term crustal movement and low-frequency, semi-continuous seismic signals. These near-annual episodes are generally considered to be related to subduction processes; however, the depths of tremor sources and their relation to the subduction interface remain uncertain. This study presents a modified version of the Seismicity-Scanning based on Navigated Automatic Phase-picking (S-SNAP) method (Tan et al., 2019), which is used to examine tremor source distribution. The modified S-SNAP method includes a sequence of the Source Scanning Algorithm (Kao and Shan, 2004), cross-correlation-based onset-time determination, the maximum intersection location technique (Font et al., 2004), and a maximum likelihood inversion. The modified S-SNAP method produces a selective catalogue of high-quality location solutions, each of which are represented by a 4D probability distribution. Tremor from select recent episodes are located using all available seismic stations, including the PGC/IOS Seismic Array (PISA), and analyzed with respect to independent tremor locations and the subduction plate interface. The goal of this research is to locate ETS tremor with improved spatial resolution using no a priori information about source locations. Understanding the nature of tremor may improve our understanding of the Cascadia subduction zone structure and its potential for megathrust earthquakes.

Presenting Author: Madison Bombardier

Student Presenter: Yes

Day: 4/21/2021

Time: 5:00 PM - 6:15 PM Pacific

Additional Authors