The Source Physics Experiments Large N Array

Seismological Research Letters2018Vol. 89(5), pp. 1618–1628

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R. J. Mellors, Arben Pitarka, E. Matzel, S. A. Magana-Zook, Douglas Knapp, W. R. Walter, Ting Chen, Catherine Snelson, Robert Abbott

Abstract

To improve the understanding of S wave generation from an explosion, a temporary deployment of 996 geophones, including both one component (Z) and three component sensors (3C), was installed from April 15 to May 23, 2016 at the Nevada National Security Site (NNSS). Sensor spacing varied from 25 to 100 m and consisted of 500 Z and 496 3C 5-Hz geophones. Data were continuously recorded during the deployment at low-gain (0 db) from April 15 to April 28 and high-gain (36 db) from April 29 to May 23. A buried (76.5 m depth) 5035 kg TNT equivalent chemical explosion (SPE-5) was recorded on April 26. It was situated in a weathered granite body surrounded by volcanic tuffs, Paleozoic carbonates, and alluvium. The array was deployed approximately 400 to 3000 m from the explosion. A set of large weight-drop shots (13,000 kg source) at 53 locations both inside and outside the geophone array were also recorded, as were local, regional, and teleseismic earthquakes. Data recovery was good, with 95% of data recovered from the chemical explosion and up to 99% in the following weeks, including both the weightdrop shots campaign and the continuous data. Important initial results from the deployment include estimates of the spatial correlation length of velocity heterogeneities and a higher resolution velocity model. Observations of the data and synthetics, indicate that some far-field (elastic) S wave energy is generated by scattering and conversion outside the near-field (inelastic) region. Interferometric processing was conducted on a Hadoop ‘big-data’ cluster.

Citations Over TimeTop 11% of 2018 papers

Abstract

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