Abstract

Anthropogenic fluid injections at depth induce seismicity which is generally organized as swarms, clustered in time and space, with moderate magnitudes. Earthquake swarms also occur naturally in different tectonic contexts. While some similarities between natural and injection-induced swarms have already been observed, whether they are driven by the same mechanism is still an open question. Indeed, they are commonly related to fluid pressure processes, while recent observations suggest the presence of aseismic slip driving seismicity. Based on such observations, we propose a simple model that combines fluid and aseismic processes, in which seismicity is triggered by fluid-induced aseismic slip. The model reconciles the seismicity migration observed in natural and anthropogenic swarms, and allows us to quantify the seismic-to-total moment ratio. By validating our approach using 22 earthquake swarms, both from natural and anthropogenic origins, our findings provide a generic explanation of the swarm driving process.