Complex Fault Geometry of the 2020 Mww6.5 Monte Cristo Range, Nevada Earthquake Sequence
Session: Intermountain West Earthquakes in the Spring of 2020 II
Type: Oral
Date: 4/20/2021
Presentation Time: 05:30 PM Pacific
Description:
On 15 May 2020 an M6.5 earthquake occurred beneath the Monte Cristo Range in the Mina Deflection region of western Nevada. Rapid deployment of eight temporary seismic stations enable detailed analysis of its productive and slowly decaying aftershock sequence (p=0.8) which included ~18,000 autodetected events in 3.5 months. Double-difference, waveform-based relative relocation of 16,714 earthquakes reveals a complex network of faults, many of which cross the inferred east-northeast-striking, left-lateral mainshock rupture. Seismicity aligns with left-lateral, right-lateral, and normal mechanism moment tensors of 128 of the largest earthquakes. The mainshock occurred near the middle of the aftershock zone at the intersection of two distinct zones of seismicity. In the western section, numerous subparallel, shallow, north-northeast-striking faults form a broad flower-structure-like fault mesh that coalesces at depth into a near-vertical, left-lateral fault. We infer this to be a region of significant slip in the mainshock and an eastward extension of the left-lateral Candelaria fault. Near the mainshock hypocenter, seismicity occurs on a northeast-striking, west-dipping structure which extends north from the Eastern Columbus Salt Marsh normal fault. Together, these two intersecting structures bound the Columbus Salt Marsh tectonic basin. East of this intersection and the mainshock hypocenter, seismicity occurs in a narrow, near-vertical, east-northeast-striking fault zone through to its eastern terminus. At the eastern end, the aftershock zone broadens and extends northwest towards the southern extension of the northwest-striking, right-lateral Petrified Springs fault system. The eastern section hosts significantly fewer aftershocks than the western section, but has more moment release. We infer that shallow aftershocks throughout the system highlight fault-fracture meshes that connect mapped fault systems at depth. Comparing earthquake data to surface ruptures and a simple geodetic fault model sheds light on the complexity of this recent M6.5 Walker Lane earthquake.
Presenting Author: Christine J. Ruhl
Student Presenter: No
Authors
Christine Ruhl Presenting Author Corresponding Author cruhl@utulsa.edu The University of Tulsa |
Emily Morton emilymorton@unr.edu Nevada Seismological Laboratory, University of Nevada, Reno |
Jayne Bormann jbormann@unr.edu Nevada Seismological Laboratory, University of Nevada, Reno |
Rachel Hatch-Ibarra rhatch@unr.edu Nevada Seismological Laboratory, University of Nevada, Reno |
Kenneth Smith ken@unr.edu Nevada Seismological Laboratory, University of Nevada, Reno |
Gene Ichinose ichinose1@llnl.gov Lawrence Livermore National Laboratory |
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Complex Fault Geometry of the 2020 Mww6.5 Monte Cristo Range, Nevada Earthquake Sequence
Category
Intermountain West Earthquakes in the Spring of 2020