Results of a VSP experiment at the Resurgent Dome, Long Valley caldera, California

A vertical seismic profiling experiment has been conducted at the DOE well LVF 51-20 at the resurgent dome at Long Valley caldera, California. The current paper is intended to report the velocity results derived from this experiment to seismically constrain the area around the resurgent dome. We report the results of velocity logs, V-p/V-s ratios, and VpVs products for the depth interval from 880-1980 m. The Bishop tuff can be divided into three zones (top-to-bottom) of intermediate velocities (V-p approximate to 4.0 km/s, V-s approximate to 2.3 km/s), followed by higher velocities (V-p = 4.7 km/s, V-s = 2.9 km/s) in the lower-central part, and a decrease back to the lower values at the bottom of the sequence. The analysis of VpVs data suggested a decrease in porosity in the lower-central section of the tuff as a possible explanation, which was supported by direct density measurements from a nearby location.