Hydro‐Mechanical Controls on Swarm Recurrence on the Westernmost Gofar Transform Fault, East Pacific Rise

Abstract Swarms are microearthquake clusters governed by aseismic deformation, fluid migration, and stress changes, but the underlying mechanisms for their recurrence remain elusive. In 2008, abundant swarms were observed on the westernmost Gofar transform fault. Microearthquake clustering reveals five distinct fluid chambers: three active before the September mainshock, generating quasi‐periodic swarms and inter‐chamber migration, and two new chambers that emerged afterward, exhibiting spatial independence and disrupted periodicity. A conceptual hydro‐mechanical fault model, incorporating creep‐driven compaction, shear‐induced dilatancy, elastic stress transfer, and rate‐and‐state friction, reproduces the main features of these swarms and perturbation by the mainshock. Results suggest that compaction‐dilatancy cycles within individual chambers, along with chamber interactions, control swarm periodicity. Mainshock‐induced stress resets the fault's hydro‐mechanical‐chemical state, and altered compaction rates could perturb swarm recurrence. This self‐organizing cycle links swarms to fluid overpressure and stress redistribution, offering an alternative physical framework for explaining various fault slip modes across active fault systems.