Profiles of volumetric water content in fault zones retrieved from hole B of the Taiwan Chelungpu‐fault Drilling Project (TCDP)

Abstract

To determine the distribution pattern of water content in the three major fault zones penetrated by the Taiwan Chelungpu‐fault Drilling Project (TCDP) hole B, and to assess a rapid, nondestructive water content measurement technique, time domain reflectometry (TDR), we determined the volumetric water content of sequential core samples and found that water content increased toward the center of each of the three fault zones, except in the disk‐shaped black material. We observed distinct anomalies in the water content and resistivity profiles, particularly in the shallowest major fault zone (FZB1136), supporting the hypothesis that FZB1136 ruptured during the 1999 Chi‐Chi earthquake. This study, the first successful application of the TDR technique to determine water content of core samples, including fault zone samples, collected by an active‐fault drilling project, showed that this technique is suitable for measuring water content of fault core samples.