Coda Wave Interferometry (CWI) is a potential source of new information on simultaneous changes in seismic velocity and the locations of earthquakes induced by subsurface engineering projects. Here we investigate the sensitivity of CWI to the contamination of recorded signals by measurement noise, and the robustness of estimates of simultaneous changes in the medium’s velocity and the locations of induced acoustic emissions, as analogues of larger scale earthquakes. We conduct numerical experiments with finite-difference modelling in media constructed using real-rock x-ray micro-tomography volumes, and generate realistic synthetic ambient noise based on the frequency-domain characteristics of laboratory-measured noise. CWI is shown to be more accurate and reliable in estimating changes in velocity and source location compared to conventional phase picking methods in heterogeneous media, particularly in the presence of noise. When simultaneous perturbations of velocity and source locations occur, CWI estimates of source perturbation remain accurate in the presence of a velocity perturbation. However, estimates of velocity perturbation exhibit errors of up to 0.5% in the presence of source perturbations of around one wavelength. These results demonstrate the potential of CWI to be used to characterize the response of rocks to stress during laboratory deformation experiments, and with suitable scaling to field-scale applications.
Presentation Date: Monday, October 15, 2018
Start Time: 1:50:00 PM
Location: 208A (Anaheim Convention Center)
Presentation Type: Oral