Time Lapse Monitoring of Acoustic Emissions With Coda Wave Interferometry

Gre⁁t, Alexandre (Department of Geophysics and Center for Wave Phenomena, Colorado School of Mines) | Snieder, Roel (Department of Geophysics and Center for Wave Phenomena, Colorado School of Mines) | Scales, John (Department of Geophysics and Center for Wave Phenomena, Colorado School of Mines) | Batzle, Mike (Center for Petrophysics, Colorado School of Mines)

OnePetro 

Summary

The coda of a waveform consists of that part of the signal after the direction arriving phases. At late times the coda is dominated by multiply scattered waves. Small changes in a medium, which would have no detectable influence on the first arrivals, are amplified by the multiple scattering and may be seen readily in the coda we have exploited ultrasonic coda waves to study the non-linear temperature dependence on velocity in granite. This non-linear is irreversible and is related to acoustic emission during thermal cracking. With the coda waves interferometer we can measure velocity difference of the order of 0.1% with an error of 0.02%.