Rock Deformation Monitoring Using Monte Carlo Waveform Inversion. Issue 10 (5th October 2021) - Lai, Ssu‐Ting
Abstract: We estimate elastic and anelastic parameters and their evolution during laboratory rock deformation experiments, while developing a Monte Carlo waveform inversion. The transducer‐to‐transducer one‐source one‐station active seismic data of dry and water‐saturated samples are obtained from Zaima and Katayama (2018), https://doi.org/10.1029/2018JB016377 . We first performed a trial‐and‐error estimate of the boundary conditions in order to suppress its influence on waveforms. The synthetic seismic data were generated using equivalent homogeneous models with different combinations of elastic and anelastic parameters with the aid of spectral element method. We compared them with the laboratory experimental data. Based on the comparisons, we obtained the time‐lapse variations of seismic velocities and attenuation of rock samples during deformation experiments, which we interpreted as crack developments. Our simultaneous estimation of elastic and anelastic parameters allowed us to detail the dynamics prior to the rock failure. Plain Language Summary: We developed a novel methodology to monitor the rock deformation in the laboratory using active seismic waveforms, comparing them against 3D synthetic seismograms. Our methodology can invert for the P‐ and S‐wave velocity changes as well as their attenuation quality factors. Changes in velocity and attenuation show the different trends especially just before rock failure, indicating the complexity of microcracks' evolution. Key Points: 3D numerical modeling with proper physical setting can simulate the waveforms in laboratory rock experiments Monte Carlo waveform inversion for velocity and attenuation structure can image velocity and attenuation changes during rock deformation Changes in velocity and attenuation show the different trends especially before rock failure