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Using Dense Nodal Geophone Data to Refine Rock Valley Fault Zone Earthquake Locations

Description: 

Analysis of earthquake locations using spatially distributed broadband seismic network stations provides well constrained hypocenters but can produce uncertainties of a few kilometers. To refine earthquake locations in the Rock Valley Fault Zone (RVFZ), we leverage a dense 3 component nodal geophone array to augment the regional seismic network operated by the University of Nevada, Reno (UNR). The geophone array is configured with 2 north-south trending lines approximately 5 km long, and 3 east-west trending lines ranging from 1 to 2 km in length. Geophone timing is evaluated against the permanent seismic station RTPP, located within 100 meters of the nodal array. Geophone arrivals are auto-picked using the Machine Learning (ML) application Earthquake Transformer (ET) for events, and event times from the UNR regional earthquake catalog. Quality metrics are applied to the ET geophone picks, including omitting stations with unfavorable noise characteristics or where the pick time deviates substantially from those made manually at station RTPP. Since this data set includes earthquakes as small as ml -0.5+ in the RVFZ, relatively fewer geophone picks are available for small events. Locations using both network and geophone array picks provide refined depth estimates and reduced error ellipses relative to locations using only network picks. Results are integrated into the Geologic Framework Model (GFM) of Rock Valley, a 3D earth model that includes seismo-stratigraphic surfaces and 3D fault models.

This work was done by Mission Support and Test Services, LLC, under Contract No. DE-NA0003624 with the U.S. Department of Energy and the NNSA Office of Defense Nuclear Nonproliferation. DOE/NV/03624--1539.

Session: It’s All About Relocation, Relocation, Relocation

Type: Oral

Date: 4/20/2023

Presentation Time: 05:30 PM (local time)

Presenting Author: Michelle E. Scalise

Student Presenter: No

Invited Presentation: 

Authors