A Review of Methods for Measuring Dynamic Characteristics of Fault Gouge
Seong-Woo MOON#+, Yong-Seok SEO
Chungbuk National University, Korea, South

The methods for measuring P- and S-wave velocities were reviewed to obtain the dynamic characteristics of fault gouge, calculated from the P- and S-wave velocities. Ultrasonic tests employ a higher frequency source than in seismic surveys, which can reduce the accuracy of the measured data via scattering and attenuation losses in porous fault gouge. Borehole surveys, such as down-hole, up-hole, and cross-hole surveys, as well as suspension P-S (SPS) logging, measure the velocities of the surrounding rocks, including fault gouge. The measured velocities can also be somewhat high or low due to the borehole casing, which is installed to prevent the collapse of weak fault gouge in the borehole wall. Seismic survey using direct waves and multichannel analysis of surface waves (MASW) surveys were conducted on a trial basis to obtain the dynamic characteristics of fault gouge. The elastic wave velocities from the seismic survey are reliable based on the first arrival calculations, and the S-wave velocity was verified by identifying the polarity reversal. Meanwhile, a low S-wave velocity was measured during the MASW survey. It is regarded as the reason why the analyzed surface wave was produced in a near-surface zone that contains different geological structures like faults, which lower the S-wave velocity by inducing the reflection of ground roll.This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2021R1I1A1A01040298).