Signal enhancement with ‘‘Mach–Čerenkov’’ waves

Abstract

A novel tool is introduced into acoustic and seismic exploration, the primary aim of which is to enhance the amplitudes of seismic signals interacting with material discontinuities and structural contrasts in sedimentary formations. This is achieved by creating a moving source with supershear or even superdilatational velocity, and recording the ensuing Mach waves on arrays of sensors. The theory shows that the spectral enhancement factor of a single sensor equals kΔ, where k=ω/C0 and Δ is the horizontal separation of the moving-source line and the sensor line. For Δ=120 ft, f=100 Hz, and C0=8000 ft/s, this factor is about 10. This ratio can be further increased by summing the output of a sensor array. A number of field experiments are suggested to test the theory.