Detecting near-surface objects with seismic waveform tomography

摘要

Three shallow, high-velocity, rubble-filled targets are imagedusing waveform tomography in an engineering-scaleclay embankment at Seven Sisters Falls, Manitoba, Canada,to locate targets buried at approximately 7 mas a blind test ofgeophysical imaging methods. Previous studies use near-offsetreflection methods to image the targets; however, this testuses waveform tomography of the long-offset, refracted arrivalsto image P-velocity and seismic attenuation. The targetsare invisible to standard traveltime tomography. Usingweight-drop data, with frequencies of 20–150 Hz, the subwavelengthtargets are resolved in the velocity images andcomplementary images of seismicQ are produced. The interpretedtarget locations are consistent with limited survey informationfrom the embankment construction. Multiple quality-control efforts, paired with a very good fit between modeland observed data, indicate the reliability of the results.