Chapter 12: Void Detection Using Near-surface Seismic Methods
Steven D. Sloan, Shelby L. Peterie, Julian Ivanov, Richard D. Miller, Jason R. McKenna, 2010. "Void Detection Using Near-surface Seismic Methods", Advances in Near-surface Seismology and Ground-penetrating Radar, Richard D. Miller, John H. Bradford, Klaus Holliger
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Detection of anomalies such as voids in the shallow subsurface using noninvasive geophysical techniques has proved to be challenging at best. Three near-surface seismic methods are introduced, including diffracted body waves, backscattered surface waves, and changes in reflection moveout velocities to detect voids directly or their effects on surrounding material properties using different parts of the wavefield. Examples are presented, including modeled and field data sets to demonstrate each technique. Body-wave diffractions were used to identify and locate man-made tunnels in multiple geologic settings. Variations in shear-wave reflection velocities are shown to correlate to changes in stress over known void locations; backscattered surface waves are shown to correlate with a known void location. Results of the studies show that the field data correlate well with the synthetic, and these methods show promise in furthering the ability to locate subsurface voids and their effects on the surrounding media.
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Near-surface seismology and ground-penetrating radar (GPR) have enjoyed success and increasing popularity among a wide range of geophysicists, engineers, and hydrologists since their emergence in the latter half of the twentieth century. With the common ground shared by near-surface seismology and GPR, their significant upside potential, and rapid developments in the methods, a book bringing together the most current trends in research and applications of both is fitting and timely. Conceptually, near-surface seismology and GPR are remarkably similar, and they share a range of attributes and compatibilities that provides opportunities to integrate processing and interpretation workflows, which makes them a perfect pair to share pages in a book.
With growth in numbers and professional emphasis have come sections, focus groups, and even professional societies specifically promoting near-surface geophysics. The emergence of near-surface geophysics groups, beginning in the late 1990s and extending into the early twenty-first century, has fueled a diversity of opportunities for professional collaborations. A range of workshops and shared publications has been the fruit of collaborative efforts. The near-surface community continues to extend and develop methods and approaches necessary to satisfy increasing demands in some of the socioeconomically pertinent disciplines such as civil and environmental engineering and hydrology. This book represents the first formal cooperative effort undertaken by the near-surface communities of the Society of Exploration Geophysicists, the American Geophysical Union, and the Environmental and Engineering Geophysical Society.