The Rock Valley Direct Comparison: Deep Core Drilling in a Unconstrained Fault Zone and Seismometer Emplacement
Colin N. Pennington, William Walter, Catherine M. Snelson, Robert Abbott, A. Christian Stanciu, Andrew Miller, Jessie Pine, C Freimuth, Ken Gaynor, Chris Carr, Jonathan Falliner, C Jewell, Ethan Alger, Matthew C. Dietel, Jessie Bonner, Ken Smith, & Moira PyleSubmitted September 7, 2025, SCEC Contribution #14416, 2025 SCEC Annual Meeting Poster #TBD
The Rock Valley Direct Comparison (RV/DC) project seeks to understand the differences between the seismic waves generated by earthquakes and explosions. To achieve this goal the experiment plans for a chemical explosion at the same depth and location as prior shallow earthquakes, recorded on common stations to allow for a direct comparison between sources. The initial step involves characterization of the site via a 2-km-deep continuously cored borehole (“Corehole”) which was completed in the spring of 2025 at the Nevada National Security Sites (NNSS). This Corehole was drilled directly through a seismically active flower structure posing a high risk for core loss.
Despite this risk, nearly 98% of core was successfully recovered. This successful drilling campaign provided important insight into previously poorly constrained subsurface geology in the area, as well as physical samples for material properties testing and structural analysis. The drilling revealed several findings including the depth of important interfaces and the intersection of multiple interpreted faults. Within the retrieved core from these sections fault structures are frequent, and contain brecciated sections, fractured core, gouge, slickenlines, and visible displacement.
Following core retrieval and detailed geophysical logging of nearly the entire borehole, and groundwater sampling at depth, a borehole seismometer array of 8 geophones with 15-m spacing was deployed at the bottom of the Corehole. Above this array, multi-mode and single-mode optical fibers allow for the collection of downhole Distributed Acoustic Sensing (DAS) and Distributed Temperature Sensing (DTS) data across the entire 2-km deep borehole. This recent deployment has already recorded shallow microseismicity occurring above the geophone array’s deployment depth. We will present an overview of the RV/DC goals along with preliminary findings from the interpretation of the core and downhole seismic recordings from the Corehole.
Prepared by LLNL under Contract DE-AC52-07NA27344; LANL contract #89233218CNA00000, and NNSS contract DE-NA0003642. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. This is LLNL abstract LLNL-ABS-2009331.
Key Words
Drilling, Borehole, Earthquake Source, Shalllow Seismicity,
Citation
Pennington, C. N., Walter, W., Snelson, C. M., Abbott, R., Stanciu, A., Miller, A., Pine, J., Freimuth, C., Gaynor, K., Carr, C., Falliner, J., Jewell, C., Alger, E., Dietel, M. C., Bonner, J., Smith, K., & Pyle, M. (2025, 09). The Rock Valley Direct Comparison: Deep Core Drilling in a Unconstrained Fault Zone and Seismometer Emplacement. Poster Presentation at 2025 SCEC Annual Meeting.
Related Projects & Working Groups
Seismology