Constraining Earthquake Nucleation using Response of Seismicity to Transient Slow-slip Event and Hydrological Surface Load
The seismicity rate often fluctuates with varying effective stress in the Earth’s crust. Common sources of stress perturbations include spontaneous slow-slip events, large-scale hydrological loading, solid Earth tides, and anthropogenic factors related to fluid injection or gas extraction. By studying how the driving stress relates to variations in seismicity rate, we can better understand the earthquake nucleation process. Here, we consider two case studies from different spatial and temporal scales. The first case study is the 2020 Westmorland, California earthquake swarm that lasted approximately five days. 5-min sampled GPS and InSAR reveal a shallow Mw 5.19 slow-slip event that started 12 hours prior to the onset of seismicity. Using a stress-driven model based on rate-and-state friction, we can explain the overall spatial and temporal evolution of seismicity using the transient stress from the slow-slip event, including the time lag between the slow-slip event and the onset of seismicity. The second case study considers the annual modulation of the seismicity rate in California. We decluster the catalog using the nearest-neighbor approach and search for periodicities using the Schuster spectrum. For areas with detectable seasonal modulation of seismicity, we find a correlation between the amplitude of seismicity rate modulation and the amplitudes of driving stress due to seasonal changes in surface hydrological loads. Furthermore, the peak seismicity rate occurs approximately one month after the peak stressing rate. Both case studies reveal that earthquake nucleation is not instantaneous. The constrained frictional-stress parameter is also consistent with one another at a few kPa, suggesting a smaller rate-and-state direct effect than those typically measured in the laboratory, the prevalence of high fluid pore pressure, or a combination, at least for the areas where the earthquakes occurred.
Session: Learning Across Geological, Geophysical & Model-Derived Observations to Constrain Earthquake Behavior [Poster Session]
Type: Poster
Room: Exhibit Hall
Date: 5/1/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Krittanon Sirorattanakul
Student Presenter: Yes
Additional Authors
Krittanon Sirorattanakul Presenting Author Corresponding Author ksirorat@caltech.edu California Institute of Technology |
Jean-Philippe Avouac avouac@caltech.edu California Institute of Technology |
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Constraining Earthquake Nucleation using Response of Seismicity to Transient Slow-slip Event and Hydrological Surface Load
Category
Learning Across Geological, Geophysical & Model-Derived Observations to Constrain Earthquake Behavior
Description