Migration diffusivity as a controlling factor in the duration of earthquake swarms

Abstract

Earthquake swarms exhibit highly uncertain temporal behavior. We investigated the relationship between the swarm duration and the diffusivity of hypocenter migration for triggered earthquake swarms in northeastern Japan. These parameters were systematically estimated by applying a diffusion model and using a unified definition of time windows for the initial and final stages of swarm activity. This approach detected a clear negative correlation between the diffusivity and swarm durations. The relation follows a power-law with an exponent of -0.5 to -1.0. Examination of published data confirmed that this relationship globally holds under various localities and tectonic environments. These results suggest that diffusivity, and by extension, crustal permeability and fluid viscosity play a key role in controlling the duration of the fluid-driven swarms. [Figure not available: see fulltext.]