Does Episodic Tremor and Slip Influence Seismicity in Northern Cascadia?

Authors

  • Madison Bombardier School of Earth and Ocean Sciences, University of Victoria, Victoria, Canada
  • Johh F. Cassidy Geological Survey of Canada-Pacific, Natural Resources Canada, Sidney, Canada
  • Stan E. Dosso School of Earth and Ocean Sciences, University of Victoria, Victoria, Canada

DOI:

https://doi.org/10.26443/seismica.v5i1.1953

Keywords:

Cascadia, episodic tremor and slip, tectonic tremor, b-value, Earthquake Statistics

Abstract

This paper presents a spatial-temporal analysis of potential links between episodic tremor and slip (ETS) and seismicity in northern Cascadia. We define spatial-temporal clusters of tremor episodes to represent ETS between 2006 and 2024, and we merge six earthquake catalogues to represent regional seismicity. The statistical analysis focuses on seismicity rates and magnitude distributions of earthquakes throughout the mid-lower forearc crust and within the subducting plate. We find that in time periods between ETS events there exist fewer M > 2.5 earthquakes in/near the ETS zone than are predicted by a best-fit Gutenberg–Richter law (GR). During ETS and shortly afterwards, M > 2.5 earthquakes in close proximity to ETS events are slightly more numerous, such that seismicity is accurately represented by the GR law. Variations in earthquake magnitudes before ETS and during/after ETS are shown to be statistically significant, although the overall average occurrence rate of M > 2.5 earthquakes per ETS event is low, at 0.8 earthquakes per ETS event. We find no statistical evidence for temporal variations in daily seismicity rates (regional and proximal to ETS) in association with ETS. We discuss several challenges in the study of this topic in Cascadia, and highlight some instances that may warrant further investigation.

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Published

2026-06-24

How to Cite

Bombardier, M., Cassidy, J. F., & Dosso, S. E. (2026). Does Episodic Tremor and Slip Influence Seismicity in Northern Cascadia?. Seismica, 5(1). https://doi.org/10.26443/seismica.v5i1.1953

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Vol. 5 No. 1 (2026)

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Copyright (c) 2026 Madison Bombardier, Johh F. Cassidy, Stan E. Dosso

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