Fluids are well known to influence earthquakes, yet rarely are earthquakes convincingly linked to precipitation. Weak modulation or limited data often leads to ambiguous interpretations. In contrast, here we find that shallow seismicity in the Sierra Nevada range near Long Valley Caldera is strongly modulated by snowmelt. Over 33 years, shallow seismicity rates were ~37 times higher during very wet periods versus very dry periods. Relative earthquake relocations from a swarm in 2017 reveal downward migration from ~1- to 3-km depth along a steeply inclined plane. Steeply dipping strata may provide high-permeability pathways and faulting plane. Here we combine the correlated seismicity and hydrologic time series with the propagation observed in the relatively relocated earthquakes. From this combined evidence, we infer that pressure diffusion from groundwater recharge dramatically accelerated shallow seismicity rates, causing seismic swarms unrelated to volcanic processes.
|Publication Subtype||Journal Article|
|Title||Snowmelt-triggered earthquake swarms at the margin of Long Valley Caldera, California|
|Series title||Geophysical Research Letters|
|Publisher||American Geophysical Union|
|Contributing office(s)||Volcano Science Center|
|Other Geospatial||Long Valley Caldera|
|Google Analytic Metrics||Metrics page|