Analysis of Three-Component Rotational and Translational Ground Motions from Source Physics Experiment Chemical Explosions and Local Earthquakes

Technical Report · Thu Dec 06 04:00:00 EST 2018

DOI:https://doi.org/10.2172/1490947· OSTI ID:1490947

Ichinose, Gene A. ^[1]; Ford, Sean R. ^[1]; Mellors, Robert ^[1]

---

1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Igel et al. (2005) demonstrated that using single point measurements of translational displacement and rotational strain can reconstruct the long-period teleseismic wavefield including wave-type, apparent velocity and propagation direction. We examine if this also holds true for higher frequencies at local distances. Four co-located three-component (3C) Eentec R-1 rotational velocity sensors and Kinemetric 3C accelerometers were deployed at the Nevada National Security Site (NNSS) to record 3 Source Physics Experiment (SPE) chemical explosions with yields of 90kg (SPE-1), 997kg (SPE-2), and 905kg (SPE-3) equivalent TNT. The four sensors were deployed 1-km from the source on granite, sedimentary, and alluvium outcrops. Three small earthquakes were also recorded, a Ml 3.3 at 28 km, a Ml 2.6 at 58 km, and Ml 3.5 at 123 km distance from SPE site. From the 3C rotational and translational motions, we measured the horizontal phase velocity of 450 m/s and 1125 m/s along two separate directions from the source consistent with near-surface geology. In contrast, the horizontal phase velocity measured for the Ml 3.3 earthquake is 5.4 km/s in the 0.1 to 10 Hz band with a propagation direction consistent with the epicenter location. While the earthquake exhibited very high coherency between 3C rotational and translational motions, the explosions exhibited more coherency with P-SV waves but less for SH-waves. This may be due to explosion SH waves originating from motions along joints or scattering near the source. This difference could be exploited as a discriminant between explosions and earthquakes.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: AC52-07NA27344
• OSTI ID: 1490947
• Report Number(s): LLNL-TR--763703; 953436
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES