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Published August 2011 | Published
Journal Article Open

Velocity and Attenuation Characterization of the LIGO Site near Livingston, Louisiana

Abstract

In April of 2009 a seismic survey utilizing explosive charges took place in Livingston parish, Louisiana. The area of the survey encompassed the location of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Livingston interferometer. In this paper, we present an analysis of seismic data recorded with three of the LIGO seismometers and a geophone array that was deployed during the time of the survey. In particular, the geophone-array data are used to study the propagation of surface waves, whereas first-arrival measurements with the LIGO seismometers provide estimates of the speed of compressional seismic waves as a function of depth. We find that fundamental Rayleigh waves have a speed close to 205 m/s consistent with results from previous borehole tests and that speed of compressional waves is 1650 m/s at 25 m depth, increasing to 2300 m/s at 1 km depth. Blast spectra are further investigated to determine the Q value of the ground medium experienced by Rayleigh waves (f > 1 Hz) and body waves deeper underground. The estimated Q value is approximately 50 for the surface waves and exceeds a value of 190 for body waves propagating at depths below 100 m.

Additional Information

© 2011 Seismological Society of America. Manuscript received 12 April 2010. J. H. thanks the Laser Interferometer Gravitational-Wave Observatory Laboratory for the unique opportunity to be involved in the geoseismic survey and the analysis of the blast data. We are deeply indebted to Nancy Erickson, who helped us with the setup of the geophone array during her spring vacation. Thanks to Juan M. Lorenzo for many fruitful discussions and for providing the geophones and to Danny Sellers and Carl Adams, who operated the geophone array for the last couple of days.

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August 19, 2023
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