The USGS conducted a seismic-refraction survey in the Mono Craters-Long Valley region of eastern California during the months of July and August, 1983, as part of a multi-disciplinary investigation of the Mono Craters area sponsored by the Office of Basic Energy Science of the Department of Energy. This experiment is part of a continuing investigation to evaluate the Mono Craters structure as a possible site for deep scientific drilling and, in particular, to assess the possibility that a youthful magma chamber may reside in the upper curst beneath the Mono Craters structure. Full size version of plates available in additional file with the report.