The Role of Slow Slip Events in the Cascadia Subduction Zone Earthquake Cycle

Authors

Juliette P. Saux, Smith College
Elias G. Molitors Bergman, Smith College
Eileen L. Evans, California State University, Northridge
John P. Loveless, Smith CollegeFollow

Document Type

Article

Publication Date

2-1-2022

Publication Title

Journal of Geophysical Research: Solid Earth

Abstract

Slow slip events (SSEs) detected on the Cascadia Subduction Zone interface at 30–50 km depth imply a release of accumulated strain. However, studies of interseismic deformation in Cascadia typically find coupling on the upper 30 km of the interface, which is generally accepted as defining the seismogenic zone. Estimates of coupling using net interseismic velocities (including SSE effects) and restricting coupling to the shallow interface may underestimate slip deficit accumulation at depths >30 km. Here, we detect reversals in GPS motion as indications of SSEs, then use SSE displacements to estimate cumulative slow slip from 2007 to 2021. We calculate pure interseismic velocities, correcting for SSE displacements, and use them to constrain an elastic block model, estimating slip deficit on the subduction interface down to 50 km. By evaluating slip deficit and slow slip independently, we examine SSEs’ effect on interseismic strain accumulation, and the effect of inter-SSE slip deficit and slow slip on vertical deformation of the forearc. We find that moderate to high coupling extends to 40 km depth, and while shallow coupling is consistent with previous estimates of the seismogenic zone, a deeper region of slip deficit beneath the Olympic Peninsula may be partially (61%) relieved aseismically by SSEs. Patterns of surface uplift suggest that complete relief of deep coupling over multiple decades may be accomplished by time-varying rates of aseismic slip.

Keywords

Cascadia, coupling, GPS, slow slip, subduction

Volume

127

Issue

2

DOI

10.1029/2021JB022425

ISSN

21699313

Rights

© 2022. American Geophysical Union.

Comments

Archived as published.

Recommended Citation

Saux, Juliette P.; Molitors Bergman, Elias G.; Evans, Eileen L.; and Loveless, John P., "The Role of Slow Slip Events in the Cascadia Subduction Zone Earthquake Cycle" (2022). Geosciences: Faculty Publications, Smith College, Northampton, MA.
https://scholarworks.smith.edu/geo_facpubs/184