Thomas B Thompson, Brendan J Meade

The Cascadia subduction zone hosts great $\mathrm{M}_\mathrm{W} > 8.5$ earthquakes, but studying these events is hindered by our short observational record. Earthquake cycle simulation provides an alternative window into the behavior of the subduction zone. Here, we present simulations over 3,800 years, 14 ruptures and hundreds of slow slip events on a high-fidelity geometric representation of the Cascadia subduction zone beneath surface topography. The boundaries of these ruptures are defined by ephemeral stress barriers that last for several cycles but are eliminated by a barrier-crossing rupture. Thus, it is possible that many real world rupture barriers are due to remnant stress shadows from previous slip events and may not persist over several earthquake cycles. In addition, we see ``fast slow slip events with $\mathrm{M}_\mathrm{W} \approx 8$. These events may occur in nature and reduce the seismically available moment or they may be a spurious feature of an unrealistic friction law.