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Dr. David Shelly, Research Geophysicist at the US Geological Survey, presents "Earthquake swarms in high definition: migrating seismicity and fluid-faulting interactions beneath Long Valley Caldera, California" at the MIT Earth Resources Laboratory.

"Earthquake swarms are common signatures of unrest in both volcanic and tectonic environments. Their interpretation rests upon an understanding of underlying physical processes, yet routine network processing typically provides limited information in this regard. To address this issue, we have developed waveform-based processing that leverages the existing catalog of earthquakes to detect and characterize events absent in routine catalogs.  Using large-scale waveform cross-correlation between cataloged events with 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 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).  Application to a 2014 swarm in Long Valley Caldera, California, illuminates complex patterns of faulting that would have otherwise remained obscured.  Together, these patterns imply strong interactions between fluid diffusion and faulting processes in the crust."