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

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