Compact Seismicity Bursts Have Different Characteristics from Background Seismicity in both Southern California and Japan
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Nicolas DeSalvio
UC San Diego
- Date & Time
- Location
- Hybrid In-Person and Online seminar via Microsoft Teams
- Host
- Jeanne Hardebeck
- Summary
Sequences of earthquakes are driven by stress perturbations and time-dependent geophysical processes. Understanding these earthquake clustering patterns and how they change in time and space can provide insights into the evolution of fault zone processes and conditions. Here we systematically identify seismicity bursts throughout southern California and Japan using new statistical methods, and examine their causes with other independent geophysical observations. We find frequent seismicity bursts across both regions. These seismicity bursts are highly compact in space and time, showing low b-values, low stress drops, and varied stress ratios compared to background seismicity. These observations indicate that the seismicity bursts may be explained by a combination of transient processes acting frequently across fault networks. Further, we observe a significant, widespread increase in seismicity bursts along the active volcanic front in Japan’s northeastern Honshu arc after the Tohoku-oki earthquake. This systematic change in behavior extends beyond 10 years, reflecting lasting changes in the stress state and local fault-zone conditions. The seismicity bursts in southern California and Japan suggest that transient fault zone processes are sensitive to perturbations, and these seismicity bursts are likely an intrinsic feature of evolving fault systems and can provide a new dynamic window into resolving short-term earthquake nucleation processes.