Time-Lapse Elastic Properties of Cracked Granite During Deformation Inferred from Laboratory Experiments Using 2-D Waveform Modelling
S. Lai, N. Fuji and I. Katayama
Event name: 81st EAGE Conference and Exhibition 2019
Session: Poster: Seismic Modelling B
Publication date: 03 June 2019
Info: Extended abstract, PDF ( 3.35Mb )
Price: € 20
In order to understand the physics of earthquake generation, we study the microscopic weakening process in a centimetre-scale laboratory experiment. A series of deformation experiment was performed to the granite sample from Aji region, Japan. During the experiments, active seismic wave propagation was measured. This study numerically models the observed waveform in order to infer to the time-lapse elastic structure changes. We first modify the finite difference code on collocated Cartesian introducing zig-zag free-surface discontinuities. We applied response function estimation to the synthetic waveform to consider all the effect (i.e. 3-D effect, instrumental response, attenuation). We use trial-and-error method to find the best-fit velocity models using full waveform synthetics with response. Then we use the same method to make a series of velocity models for the automated Monte Carlo scheme. Comparing automated velocity models using different methods, we find that L1 norm is the best fitting method. We further tested fault models that we find the trend of the changes of the velocity model after the creation and during the thickening of the fault. This method will detail a microscopic weakening process during the nucleation of earthquakes using full waveforms, which have an impact on fundamental understanding of earthquake physics.