A trial to reveal stress recovery at Nojima fault after the 1995 Kobe earthquake by core-based measurement methods

摘要

In order to reveal stress recovery at Nojima fault after the 1995 Mw 6.9 Kobe earthquake, Japan, we carried out in-situ stress measurements by using core samples obtained from a vertical scientific drilling penetrated through the Nojima fault which ruptured during the Kobe earthquake. The drilling operations were conducted from 2016 to 2017, therefore the measured stress data using the core samples should be as the time of stress relief i.e. the same as the drilling time, ～22 years passed after the earthquake. We applied two core-based stress measurement methods called Anelastic Strain Recovery (ASR) and Diametrical Core Deformation Analysis (DCDA). Although we are continuously working on core re-orientation and discussions on how interpret the measured stress state, and have not reached conclusions, we believe that a useful data set of the current state of stress around Nojima fault has been obtained by using the two core-based stress measurement methods.