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Compiled onshore and offshore paleoseismic data along the Cascadia Subduction zone

March 5, 2024

The USGS Powell Center Cascadia earthquake hazards working group compiled published onshore and offshore paleoseismic data along the Cascadia subduction zone, spanning sites from Vancouver Island to the Mendocino triple junction. Evidence for megathrust rupture includes coastal land-level change, tsunami inundation, onshore shaking proxies such as landslides or liquefaction, and offshore shaking proxies such as marine turbidites. The quality of paleoseismic data for megathrust rupture along the Cascadia subduction zone collected over the past three decades varies because analytical capabilities and data collection methodologies have evolved. Thus, as part of the compilation, we also present a ranking scheme to assess the quality of age estimates and evidence for great megathrust rupture. With the age ranking scheme, we ask: "How well is a proposed paleoseismic event dated?" based on the materials and methods used. With the evidence ranking scheme, we ask: "How confident are we that a proposed event is, in fact, the result of a Cascadia megathrust rupture?" based on the sedimentological characteristics, correlation, and mapping. The evidence ranking scheme also helps to evaluate possible alternative mechanisms for creating paleoseismic evidence such as crustal fault, intraslab, or distant tsunamigenic earthquake.

Publication Year 2024
Title Compiled onshore and offshore paleoseismic data along the Cascadia Subduction zone
DOI 10.5066/P13OJQYW
Authors Lydia M Staisch, Robert C Witter, Janet T Watt, Alex R Grant, Maureen A Walton, Daniel Brothers, Elizabeth Davis, Cristina Dura, Simon Engelhart, Randolf Enkin, Carolyn Garrison-Laney, Christopher Goldfinger, Tark S Hamilton, Andrea Hawkes, Jenna C Hill, Isabel Hong, Bruce E Jaffe, Harvey Kelsey, Sean R Lahusen, SeanPaul M. La Selle, Alan R Nelson, Nora M Nieminski, Jason S Padgett, Jason (Contractor) V Patton (Contractor), Jessie K Pearl, Jessica Pilarczyk, Brian Sherrod, Kelsay Stanton
Product Type Data Release
Record Source USGS Digital Object Identifier Catalog
USGS Organization Geology, Minerals, Energy, and Geophysics Science Center