Fluid-faulting interactions: Fracture-mesh and fault-valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm

David R. Shelly; Taka’aki Taira; Stephanie G. Prejean; David P. Hill; Douglas S. Dreger

doi:10.1002/2015gl064325

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Fluid-faulting interactions: Fracture-mesh and fault-valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm

David R. Shelly·Taka’aki Taira·Stephanie G. Prejean·David P. Hill·Douglas S. Dreger

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Abstract

Faulting and fluid transport in the subsurface are highly coupled processes, which may manifest seismically as earthquake swarms. A swarm in February 2014 beneath densely monitored Mammoth Mountain, California, provides an opportunity to witness these interactions in high resolution. Toward this goal, we employ massive waveform-correlation-based event detection and relative relocation, which quadruples the swarm catalog to more than 6000 earthquakes and produces high-precision locations even for very small events. The swarm's main seismic zone forms a distributed fracture mesh, with individual faults activated in short earthquake bursts. The largest event of the sequence, M 3.1, apparently acted as a fault valve and was followed by a distinct wave of earthquakes propagating ~1 km westward from the updip edge of rupture, 1–2 h later. Late in the swarm, multiple small, shallower subsidiary faults activated with pronounced hypocenter migration, suggesting that a broader fluid pressure pulse propagated through the subsurface.

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Source-reported bounding extent: 37.59° to 37.66° latitude; -119.09° to -119° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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David R. Shelly, Taka’aki Taira, Stephanie G. Prejean, David P. Hill, Douglas S. Dreger. 2015-07-23. Fluid-faulting interactions: Fracture-mesh and fault-valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm. https://doi.org/10.1002/2015gl064325

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