Orbital vibrator seismic source for simultaneous P‐ and S‐wave crosswell acquisition

Abstract

A recently developed borehole seismic source, the orbital vibrator, was successfully deployed in a crosswell survey in a fractured basalt aquifer. This seismic source uses a rotating eccentric mass to generate seismic energy. Source sweeps with clockwise and counter‐clockwise rotations are recorded at each source location. Because this source generates circularly polarized waves, unique processing algorithms are used to decompose the recordings into two equivalent linearly oscillating, orthogonally oriented seismic sources. The orbital vibrator therefore generates P‐ and S‐waves simultaneously for all azimuths. A coordinate rotation based on P‐wave particle motion is used to align the source components from various depths. In a field experiment, both P‐ and S‐wave arrivals were recorded using fluid‐coupled hydrophone sensors. The processed field data show clear separation of P‐ and S‐wave arrivals for in‐line and crossline source components, respectively. A tensor convolutional description of the decomposition process allows for extension to multicomponent sensors.