S041-08
The 2020 M6.5 Monte Cristo Range Earthquake and Aftershock Sequence
Friday, 11 December 2020: 11:00
Virtual
Christine J Ruhl, University of Tulsa, Department of Geosciences, Tulsa, OK, United States, Emily Morton, University of Nevada Reno, Nevada Seismological Laboratory, Reno, NV, United States, Kenneth D Smith, University of Nevada Reno, Reno, NV, United States, Jayne M Bormann, University of Nevada, Reno, Reno, United States, Rachel Lauren Hatch Ibarra, California State Polytechnic University Pomona, Pomona, CA, United States, Gene Ichinose, Lawrence Livermore National Laboratory, Livermore, CA, United States and Cleat Philip Zeiler, Mission Support and Test Services, Defense Nuclear Nonproliferation, North Las Vegas, NV, United States
Abstract:
The M6.5 Monte Cristo Range (MCR) earthquake occurred on 15 May 2020 at 11:03:27.176 UTC near Tonopah, NV within the Mina Deflection structural domain of the central Walker Lane. No apparent foreshocks have been noted. The earthquake was felt as far away as the San Francisco Bay area, CA (~410 km), Salt Lake City, UT (~600 km), and Portland, OR (~890 km). Since 1852, 26 earthquakes M6 or greater have occurred in Nevada, 23 within the Walker Lane/Eastern CA Shear Zone, with an average recurrence interval of ~6.5 years and ~7.5 years, respectively (the recurrence intervals range 0-41 years). The most recent M6 Nevada earthquake was the 2008 Mw6.0 Wells, Nevada earthquake. The MCR earthquake occurred about 195 km NE of the 2019 M7.1 Ridgecrest, 125 km E of the 1993 M6.1 Eureka Valley and 85 km NE of the Mw 6.3 Chalfant, California Walker Lane earthquakes. The MCR earthquake shows left-lateral strike slip motion striking ENE. The ~35 km long aftershock zone lies along a similar trend.
Here we present analysis of correlation-based relocations of MCR aftershocks and corresponding moment tensors to isolate mainshock, fault orientations, and overall sequence behavior. As of 14 July, 10,748 aftershocks (automatic locations only) have occurred with a median depth of 6.4 km; 43 aftershocks are M4 or larger, and 4 are M5 or larger. Eight temporary broadband and strong motions stations were operating within days of the earthquake. Also, 48 3-channel Nodal instruments, covering most of the aftershock zone, were installed on day-two of the sequence in addition to USGS nodal deployments. The aftershock distribution appears to occur on an eastward extension of the mapped surface portion of Candelaria Fault, intersecting the Benton Springs Fault at the eastern end. Preliminary relocations of the sequence indicate numerous activated structures at depth. Aftershocks through 14 July have a b-value of 0.83, and mechanisms are primarily strike slip and normal faulting.
