Observations of Seismicity in the Rock Valley Fault Zone, Southern NNSS, from deep core-hole DAS and Geophone Data

Ken Smith, Jacob Gochenour, A. Christian Stanciu, Colin N. Pennington, Reagan Turley, Maia Zhang, Abigail Travers, & Michelle Scalise

Submitted August 30, 2026, SCEC Contribution #15645, 2026 SCEC Annual Meeting Poster #TBD

The Rock Valley Direct Comparison (RV/DC) experiment, Phase III of the Source Physics Experiment (SPE), will detonate a conventional explosive near the hypocenter of the unusually shallow 1993 Mw 3.8 Rock Valley earthquake (~2 km depth) at the Nevada National Security Site (NNSS). The goal is to obtain key observations that discriminate natural earthquakes from explosive sources at regional and local scales. While a monitoring network has been active in the southern NNSS (Rock Valley) since the late 1970s, portable instruments deployed during the 1993 sequence confirmed shallow source depths. Since 2012, telemetered instrumentation has supplemented central Rock Valley monitoring in direct support of RV/DC. Special deployments include a 48-station nodal array (in continuous operations since early 2022). Initial drilling operations in 2025 successfully recovered continuous geologic core and a comprehensive suite of geophysical logs to 2 km depth. A DAS fiber optic cable and a 105 m length 8-level 3-component geophone string (at ~2 km depth) were installed in the corehole. From local earthquake monitoring, ~32K earthquakes have been included in the Nevada Seismological Laboratory’s earthquake catalog in NNSS since 2000 - the modern digital recording period. This activity spans the entire length of the Rock Valley Fault Zone, although the catalog is dominated by aftershocks of the 1992 M5.7 Little Skull Mountain earthquake. We present waveforms from earthquakes shallower than the 2 km deep geophone array, unequivocally confirming shallow source depths. High-quality cross-correlation based event locations, applying various velocity models, image shallow structures in the central Rock Valley Fault Zone to characterize the planned source region of the Phase III RV/DC experiment.

Key Words
Rock Valley Fault Zone, Distributed Acoustic Sensing (DAS), Earthquake Monitoring, Source Physics Experiment (SPE), Nevada National Security Site (NNSS)

Citation
Smith, K., Gochenour, J., Stanciu, A., Pennington, C. N., Turley, R., Zhang, M., Travers, A., & Scalise, M. (2026, 08). Observations of Seismicity in the Rock Valley Fault Zone, Southern NNSS, from deep core-hole DAS and Geophone Data. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology