Prevalence of Aseismic Slip Linking Fluid Injection to Natural and Anthropogenic Seismic Swarms

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 in various geological contexts such as subduction zones, mountain ranges, volcanic, and geothermal areas. While some similarities between anthropogenic and natural swarms have already been observed, whether they are driven by the same mechanism, or by different factors, is still an open question. Fluid pressure diffusion or aseismic deformation processes are often proposed to explain observations of hypocenters migration during swarms, while recent models suggest that swarm seismicity is rather triggered by fluid‐induced aseismic fault slip. Here, using a global compilation of 22 natural and anthropogenic swarms, we observe that duration, migration velocity, and total moment scale similarly for all swarms. This supports a common driving process for both natural and induced swarms. The scaling relations are similar to those found for slow slip events. These observations highlight the prevalence of fluid‐induced aseismic slip as main driver of earthquakes migration during swarms. After quantifying aseismic slip released in the swarms, we propose an approach to estimate the seismic‐to‐total moment ratio, which we then compare to a theoretical estimation that depends on the migration velocity of the swarm and the effective stress drop. Our findings lead to a generic explanation of the process driving earthquake swarms that might open new possibilities to monitor seismic swarms.

Updip Fluid Flow in the Crust of the Northeastern Noto Peninsula, Japan, Triggered the 2023 Mw 6.2 Suzu Earthquake During Swarm Activity

“…Geodetic data analysis suggests that aseismic deformation occurred during this swarm (Nishimura et al, 2023), and the aseismic slip occurrence during fluid migration is consistent with predictions from numerical simulations of the response of a fault under fluid intrusion (Bhattacharya & Viesca, 2019;Eyre et al, 2019;Wynants-Morel et al, 2020;Yoshida et al, 2021). Recent observations support the occurrence of aseismic slip during fluid intrusion for both natural and fluid-injection-induced seismicity (Cornet et al, 1997;Danré et al, 2022;De Barros et al, 2020;Guglielmi et al, 2015;Hatch et al, 2020;Wei et al, 2015;Yoshida & Hasegawa, 2018b;Yukutake et al, 2022). Although these multiple influences likely contributed to the generation and migration of the present sequence, the fluid supply probably played a central role, given the above observations taken together.…”

Unraveling Earthquake Clusters Composing the 2014 Alto Tiberina Earthquake Swarm via Unsupervised Learning

“…We argue that the lack of scaling can be explained by the fact that in our approach, we solely measure the seismic moment of each cluster, without accounting for the aseismic moment. The existence of a significant aseismic moment is supported by the low 𝜎 eff observed for each cluster, which indicate low asperity density in the faults (Danré et al., 2022; Fischer & Hainzl, 2017), as well as by the large ratio between the released geodetic and seismic moment (Gualandi et al., 2017).…”

“…Furthermore, events directly driven by the injection of fluids would migrate in a distinct way (Shapiro et al., 1997) for which no evidence was found within the presented study. Additionally, recent models revealed the significant role of fluids in facilitating aseismic slip, the mechanism triggering seismicity (Danré et al., 2022; De Barros et al., 2021).…”

Prevalence of Repeating Earthquakes in the Continental Crust and Subducting Slabs: Triggering of Earthquakes by Aseismic Slip

“…Recently, Danre et al. (2022) proposed, based on a systematic survey of 22 natural and anthropogenic swarms, that a fluid‐induced aseismic slip triggers earthquake swarms at different scales. Here we propose that aseismic slip is a common triggering process for all the earthquakes independent of tectonic regimes, activity types, and focal depths.…”