Evidence of Aseismic and Fluid‐Driven Processes in a Small Complex Seismic Swarm Near Virginia City, Nevada

Abstract

AbstractAnalysis of a small earthquake swarm near Virginia City, NV, reveals complex structural features, including an interplay of both fluid‐driven and aseismic‐driven earthquake migration within a naturally occurring tectonic sequence. The Virginia City earthquake sequence occurred over ~10 days in January 2014. We relocate 305 events to reveal three separate, well‐defined planar structures. The earthquakes initially migrate at a rate consistent with pore fluid diffusion, outlining a moderately dipping plane. The earthquakes then jump to a vertical plane and migrate at a higher rate; the sequence continues to migrate rapidly onto a third, shallowly dipping plane, consistent with rates observed elsewhere associated with aseismic creep. Focal mechanisms indicate right‐lateral strike slip on the vertical plane and both normal and left‐lateral strike slip movement on the other planes, and the newly imaged structures illuminate the orientation of active faults at depth in the Walker Lane tectonic region.