Seismic time reversal mirror experiment

Abstract

Time Reversal Mirror (TRM) is a method for refocusing recorded waves (including seismic) to their initial source location. Using different observation geometries, we demonstrate how seismic P- and S- energy is successfully focused back to its original location in a field experiment. Focusing resolution is within the theoretical range of half the dominant wavelength. Although the field experiment is done in controlled conditions, a-priori knowledge of seismic velocities of the medium is not necessary. In the first step the seismic wave is generated by a sub-surface point source and recorded by a surface array (the mirror). In the second step, time-reversed traces are back-propagated from the original receiver positions and recorded at locations near and at the original source location. The ability to carry out seismic TRM is dependent on a new vibrator based on a linear synchronous motor (LSM). As opposed to standard hydraulic-based seismic vibrators, the LSM-based vibrator can generate an arbitrary signal and thus re-emit recorded seismic traces back into the sub-surface. Various applications of the TRM in seismic data can be considered: enhance oil recovery by wave stimulation, fracking intensification, target oriented data acquisition etc.