Abstract

The last great megathrust earthquake in the Cascadia subduction zone occurred in AD 1700, predating the instrumental record. While modern geodetic techniques capture the ongoing interseismic deformation, paleoseismic records provide estimates of the coastal subsidence over the AD 1700 event. Here, we connect these geodetic and paleoseismic observations using a 3D quasi-dynamic earthquake cycle model. The model includes a realistic slab geometry and simulates the earthquake cycle under the assumption that the coseismic rupture is consistent with the interseismic locking pattern. The model predictions agree well with both paleoseismic estimates of coastal subsidence during and after the earthquake, as well as geodetic data on the current interseismic surface velocity field. This suggests that our rupture-locking consistency assumption is realistic for the central Cascadia subduction zone, and the rupture patches in the AD 1700 event may be persistent in the next megathrust event.