Catherine Mary Snelson

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 15 April to 23 May 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 15 April to 28 April and high gain (36 dB) from 29 April to 23 May. A buried (76.5 m depth) 5035 kg trinitrotoluene (TNT) equivalent chemical explosion (Source Physics Experiments [SPE]-5) was recorded on 26 April. It was situated in a weathered granite body surrounded by volcanic tuffs, Paleozoic carbonates, and alluvium. The array was deployed approximately 400-3000 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 weight drop 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.

Energy and natural resources are crucial to the sustainability of worldwide economies, security, and overall well-being. However, the future workforce in the energy and natural-resources sector is at risk, and meeting the challenges of this dwindling workforce requires well-educated geoscientists in exploration and applied geophysics and related geoscience and technology disciplines. Programs such as geophysical field courses that are supported by SEG and industry, in partnership with academic institutions and government laboratories, are important approaches to maintaining and enhancing expertise in exploration geophysics. One example of a geophysical field course devoted to educating our future workforce is the Summer of Applied Geophysical Experience (SAGE), a four-week program based in Santa Fe, New Mexico, designed to actively engage students in all phases of applied geophysical research. SAGE is a unique educational experience that combines teaching and research as a partnership among universities, industry, government agencies, and professional societies. SAGE teaches the principles and applications of refraction and reflection seismology, magnetics, gravity, GPS, heat flow, several electromagnetic (EM) methods, and ground-penetrating radar (GPR) in a field-based, hands-on setting. More than 850 students and qualified professionals have attended SAGE, many of whom have gone on to become leaders in academia, industry, and government. SAGE students are exposed to the exciting challenges that face earth scientists today, and they develop skills that are necessary to address the world's growing energy demands. Examples of SAGE research projects include mapping archaeological sites and tectonic structure and investigating water and geothermal resources in the Rio Grande rift.

As you receive this issue of The Leading Edge the Summer of Applied Geophysical Experience (SAGE) will be starting our 30th field season. SAGE is a unique educational program that combines teaching and research as a partnership between universities, industry, government agencies and professional societies. SAGE includes a four-week period based in Santa Fe, New Mexico and one-week workshop in the following January for undergraduates, at San Diego State University, which allows us to enhance their research experience. We teach the principles and applications of refraction and reflection seismics, magnetics, gravity, GPS, several electromagnetic (EM) methods and ground-penetrating radar (GPR) in a field-based, hands-on setting. The central research activity of SAGE is the acquisition and interpretation of geophysical field data. Students learn geophysics by doing geophysics—a discovery oriented approach.