Patch Interactions on a Heterogeneous Fault Drive Nearby Slow and Fast Earthquakes

Abstract Tectonic tremor and repeating/regular earthquakes off Iwate in the shallow Japan Trench occur episodically and in spatially overlapping areas, implying a common aseismic driver. We investigate how small aseismic slip triggers events across multiple slip‐rate regimes using fully dynamic earthquake‐cycle simulations governed by rate‐and‐state friction. Along‐fault heterogeneity is imposed by alternating velocity‐weakening (VW) and velocity‐strengthening (VS) patches, and events are classified based on peak slip velocity . A single VW patch produces only aseismic events, whereas a multi‐patch heterogeneous model generates sub‐seismic slip and earthquakes, often nearly synchronous across VW patches. Inter‐event transient slip in VS patches raises stress during subsequent VW nucleation. Transitions in and rupture properties are controlled by subtle stress differences between nucleating VW patches and surrounding VS patches. This mechanism provides a simple physical explanation for why slow and fast earthquakes can emerge from interacting fault patches with spatial overlap and close temporal proximity.