Untangling the Web of Fluids and Faulting in Earthquake Swarms

Date: 4/26/2019

Time: 02:30 PM

Room: Cascade I

Earthquake swarms are common signatures of unrest in both volcanic and tectonic environments. Their interpretation in the broader system depends upon determining the underlying physical processes driving the swarm, which can be difficult. Seismic recordings of earthquakes provide the most direct constraints on active processes in the source region, yet the limited resolution of routine processing obscures much of this valuable information. Using large-scale waveform cross-correlation between cataloged events and the continuous data stream, it's possible to detect and precisely locate many times more events than are included in standard catalogs. We have recently extended this technique to estimate relative polarities between events, facilitating robust focal mechanism estimation for large populations of tiny earthquakes, addressing a common shortcoming in microseismicity analyses (Shelly et al., JGR, 2016). Here, I explore high resolution views of recent earthquake swarms at Yellowstone and Long Valley Calderas and consider their implications for source zone physics. This analysis reveals a dramatic migration of earthquake activity with time, with complex faulting geometries. Together, these patterns imply strong interactions between fluid diffusion and faulting processes in the crust.

Presenting Author: David R. Shelly

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