Utilizing Automated Picks from the 2020 Mw 6.5 Monte Cristo Range Earthquake Sequence to Image the Aftershock Region

Joses B. Omojola, Patricia Persaud, Chiara Nardoni, & Rufus D. Catchings

Submitted September 11, 2022, SCEC Contribution #12075, 2022 SCEC Annual Meeting Poster #014

The 2020 Mw 6.5 Monte Cristo Range earthquake is the largest earthquake to occur in Nevada in 66 years. It ruptured a previously unmapped Quaternary fault in the ~80-km wide Mina Deflection region. This zone of complex faulting is interpreted to transfer slip from southern to central Walker Lane and is a major bend in pre-Cenozoic structural trends in the Walker Lane. We utilized data from a USGS rapid-response deployment of 60 nodal seismometers to develop a catalog of aftershocks with the goal of producing high-resolution images of the fault zone structure and the spatial and temporal evolution of the seismicity. Neural networks have detected smaller magnitude events than traditional methods in several studies resulting in significantly larger earthquake catalogs. However, the quality of P- and S-phase picks from such automated catalogs and the suitability of the picks for developing local earthquake tomographic models require evaluation. We first apply the EQTransformer model for event detection and locate the >19,400 events using HYPOINVERSE. The events were relocated using the double-difference method and analysis of the relocated catalog improves identification of rupture surfaces associated with the sinistral faults of the Monte Cristo Range. We further refine the initial set of phase picks by simulating synthetic travel-times with a representative initial velocity model of the area and select only phase picks that occur within 20% of the synthetic travel-times. This helps eliminate outlier picks but retains picks associated with local velocity heterogeneities. The refined catalog is then used as input for 3D body-wave tomographic and attenuation models of the Monte Cristo Range that together will improve the imaging of fault zones and the structural complexity of the aftershock region.

Key Words
Central Walker Lane, Local Earthquake Tomography, Monte Cristo Range, Seismic Attenuation

Omojola, J. B., Persaud, P., Nardoni, C., & Catchings, R. D. (2022, 09). Utilizing Automated Picks from the 2020 Mw 6.5 Monte Cristo Range Earthquake Sequence to Image the Aftershock Region. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups