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No abstract

On 15 May 2020 an Mww 6.5 earthquake occurred beneath the Monte Cristo Range in the Mina Deflection region of western Nevada. Rapid deployment of eight temporary seismic stations enabled 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 35-km-long 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 the near-vertical fault 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 that 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 toward 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 with surface ruptures and a simple geodetic fault model sheds light on the complexity of this recent M 6.5 Walker Lane earthquake.

No abstract

The Nevada Seismological Laboratory (NSL) at the University of Nevada, Reno, installed eight temporary seismic stations following the 15 May 2020 Mww 6.5 Monte Cristo Range earthquake. The mainshock and resulting aftershock sequence occurred in an unpopulated and sparsely instrumented region of the Mina deflection in the central Walker Lane, approximately 55 km west of Tonopah, Nevada. The temporary stations supplement NSL’s permanent seismic network, providing azimuthal coverage and near-field recording of the aftershock sequence beginning 1–3 days after the mainshock. We expect the deployment to remain in the field until May 2021. NSL initially attempted to acquire the Monte Cristo Range deployment data in real time via cellular telemetry; however, unreliable cellular coverage forced NSL to convert to microwave telemetry within the first week of the sequence to achieve continuous real-time acquisition. Through 31 August 2020, the temporary deployment has captured near-field records of three aftershocks ML≥5 and 25 ML 4–4.9 events. Here, we present details regarding the Monte Cristo Range deployment, instrumentation, and waveform availability. We combine this information with waveform availability and data access details from NSL’s permanent seismic network and partner regional seismic networks to create a comprehensive summary of Monte Cristo Range sequence data. NSL’s Monte Cristo Range temporary and permanent station waveform data are available in near-real time via the Incorporated Research Institutions for Seismology Data Management Center. Derived earthquake products, including NSL’s earthquake catalog and phase picks, are available via the Advanced National Seismic System Comprehensive Earthquake Catalog. The temporary deployment improved catalog completeness and location quality for the Monte Cristo Range sequence. We expect these data to be useful for continued study of the Monte Cristo Range sequence and constraining crustal and seismogenic properties of the Mina deflection and central Walker Lane.