In-situ stress measurement by the anelastic strain recovery method in WFSD-1

Abstract：The in-situ stress state of seismogenic fault after a strong earthquake is one of the important parameters for understanding the mechanism of the earthquake. The Wenchuan earthquake Fault Scientific Drilling project (WFSD) is a rapid response to the 2008 Ms 8.0 Wenchuan earthquake, which provided the test rock core for recognizing the stress state of the depth of Longmenshan fault on the eastern margin of the Tibetan Plateau. This paper focuses on the measuring instruments and processes of the anelastic strain recovery method (ASR) for the deep in-situ stress measurement. The anelastic recovery strains of seven different deep cores are in the range of 424-1173m in WFSD-1. The direction and magnitude of principal stress were determined and estimated, respectively. The dominant azimuths of maximum principal stress are between NW69° and NW35°, and the magnitude of principal stress increases with the increasing depth.