Abstract
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.