资源环境科技发展态势分析平台

Analysis 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 similar to 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.

Plain Language Summary Earthquake swarms remain an intriguing phenomenon as the characteristics and mechanics controlling their progression are poorly understood. In this work, we study a small seismic swarm in western Nevada to better understand both the progression of the swarm and the active faults in the region. The Virginia City Earthquake sequence occurred for similar to 10 days in January 2014 with over 300 events. Our analysis shows these events occurred across three distinct planes, with two different mechanisms driving the earthquake activity: pore fluid diffusion and aseismic slip. Our study demonstrates the presence of these mechanisms in this part of the Walker Lane tectonic region. Additionally, our study provides information on fault structures at depth.