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Seismogenic Depth Variation across the Transtensional Northern Walker Lane
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  • Christine J. Ruhl,
  • Rachel E. Abercrombie,
  • Rachel Lauren Hatch,
  • Kenneth D. Smith
Christine J. Ruhl
The University of Tulsa

Corresponding Author:[email protected]

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Rachel E. Abercrombie
Boston University
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Rachel Lauren Hatch
University of Nevada, Reno
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Kenneth D. Smith
University of Nevada Reno
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We calculate high-precision absolute and relative earthquake relocations to investigate the relationship between seismicity and major active faults, and to explore variation in seismogenic depths across the Northern Walker Lane. We first compute datum-adjusted and station-residual-corrected absolute relocations, before relocating events using waveform cross-correlation. Of 40,581 routinely located earthquakes between 2002 and 2018, we relocate 27,132 (66.9%) with resulting median horizontal and vertical location uncertainties less than ~100 m. We then compute 95thpercentile depths as a proxy for seismogenic depth and compare to published Moho depths. Microseismicity occurs in large highly clustered source areas, often consisting of many short, distinct fault structures. Activity concentrates near the ends of mapped Quaternary faults rather than along them. Microseismicity-defined structures in transition zones between major surface faults may identify active fault networks that link faults at the depth. Seismogenic depth shallows away from the Sierra Nevada to the east-northeast over approximately 80 km, from an approximate depth of 17 km to 13 km. This follows, to scale, the decrease in Moho depth across the same region from about 35 km to 30 km. We compare seismogenic and Moho depths to topographic relief and heat flow measurements to discuss controls on the depth of seismicity in the region. Heat flow increases smoothly over the same region of the decreasing seismogenic and Moho depth, increasing by as much as 20 mW/m2.