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TitleNovel location method for ETS tremor in northern Cascadia
AuthorBombardier, M; Cassidy, J FORCID logo; Kao, HORCID logo; Dosso, S
Source2021 Annual Meeting, Seismological Society of America, technical sessions; Seismological Research Letters vol. 92, no. 9B, 2021 p. 1461,
Alt SeriesNatural Resources Canada, Contribution Series 20200698
PublisherSeismological Society of America
MeetingSeismological Society of America 2021 Annual Meeting; April 19-23, 2021
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
Subjectsgeophysics; tectonics; Science and Technology; Nature and Environment; Health and Safety; earthquakes; earthquake risk; seismic risk; seismicity; crustal movements; seismic waves; seismic data; seismological network; seismic arrays; plate margins; crustal structure; Cascadia Subduction Zone; Seismicity-Scanning based on Navigated Automatic Phase-picking (S-SNAP); Source Scanning Algorithm; PGC/IOS Seismic Array (PISA); Methodology
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2021 04 01
AbstractEpisodic 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.
Summary(Plain Language Summary, not published)
This document highlights improvements to the methodology of locating tremors that occur during Episodic Tremor and Slip events in the Cascadia subduction zone. These tremors are not earthquakes, and have complicated waveforms - where seismic energy builds up slowly and drops off slowly. They are challenging to locate. We are using waveform correlations and improving the technique to provide more accurate locations and better depth estimates. The goal of this work is to better map out ETS events to improve our understanding of subduction earthquake hazards.

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