Comparison of seismic reflection and ground‐penetrating radar imaging at the controlled archaeological test site, Champaign, Illinois

Abstract

AbstractShallow seismic reflection and ground‐penetrating radar images were collected at a replicated burial mound in the Controlled Archaeological Test Site (CATS) in Champaign, Illinois. The CATS mound contains a pig burial within a wood‐lined crypt at a depth of 1.6–2.4 m. Seismic reflection data were collected from two different energy sources: a small (0.5 kg) hammer for an impulsive source, and a vibrator for a frequency swept source. Seismic data were collected at densely spaced points (5 cm) along a line of 48 geophone receivers. These data were stacked in a common mid‐point gather, band‐pass filtered, and processed with frequency–wavenumber migration. The seismic image produced by the hammer source was dominated by bodywaves at 120 Hz, whereas the vibrator source image was dominated by surface waves at 70 Hz. Both seismic sources revealed clear reflections from the burial crypt, and placed the top of the crypt at the correct depth with a seismic velocity of 120 m s−1. The bottom of the crypt was poorly defined by the seismic data owing to multiple reflections within the crypt. The vibrator source also revealed a high‐frequency (360 Hz) reflector at 2.7 m depth within the mound, perhaps due to a resonant cavity within the pig's body. Single channel ground‐penetrating radar data were processed with the same approach, including band‐pass filtering and migration. The radar data reveal clear reflections from the burial crypt. Extremely fast radar velocities (260 mm ns−1) are required in the upper portion of the burial mound to place the top of the crypt at its correct depth. The bottom of the crypt was well defined by ground‐penetrating radar, and was located accurately with respect to the top of the crypt with a moderate radar velocity (170 mm ns−1). The application of both seismic reflection and ground‐penetrating radar to the same site may be beneficial for improved understanding of their abilities for shallow subsurface imaging. Copyright © 2002 John Wiley & Sons, Ltd.