Earthquakes generated from bedding plane-parallel reverse faults above an active wedge thrust, Seattle fault zone

A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, bedding-plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the back-thrust. This earthquake also included slip on some of the