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Influences of intrinsic fault characteristics and external processes on swarm migration and duration,

Xiaowei Chen, & Junle Jiang

Published December 2023, SCEC Contribution #13428

Most earthquake swarms exhibit spatial migration. Diffusive migration is often associated with fluid migration, while linear migration is often associated with slow slip processes. Recent studies compared relationships between and duration, as well as migration velocity with duration, and found a systematic scaling relationship. In this study, we expand the global compilation from Danre et al. 2022 and Amezawa et al. 2021 to include earthquake swarms in Southern California and Oklahoma. The expanded compilation reveals a similar scaling relationship, but it also shows a wider range of migration velocities up to two or three orders of magnitude for the same duration. The (faster velocity) is marked by examples of pre-existing faults with larger events (M4 or 5) from southern California and Nevada, while the lower limit is marked by examples of newly created faults involving potential aseismic deformation or hydraulic processes from volcanic and geothermal fields. For some swarms, multiple migration stages can be identified (e.g., the Mogul sequence in Nevada and the Guthrie sequence in Oklahoma). Within the same fault system, the product of velocity and duration for different migration stages remains approximately constant. Those observations suggest that intrinsic fault characteristics possibly control the velocity and duration scaling. Focusing on two well-recorded swarms: the Brawley swarm and the Guthrie swarm, alternating patches of lower and higher-stress drop patches can be identified from stress drop patterns. Larger events tend to occur near higher-stress drop patches. The aseismic-slip triggered Brawley swarm initiated with higher-stress drop events, while the fluid-induced Guthrie sequence initiated with lower-stress drop smaller events. Using numerical models of faults with heterogeneous properties, we explore the influences of intrinsic fault characteristics and external stress perturbations on swarm migration and evolution.

Chen, X., & Jiang, J. (2023, 12). Influences of intrinsic fault characteristics and external processes on swarm migration and duration,. Oral Presentation at AGU fall 2023.