Determining In-Situ Stress State by Anelastic Strain Recovery Method Beneath Xiamen: Implications for the Coastal Region of Southeastern China

• Published in: Rock mechanics and rock engineering Vol. 55; no. 9; pp. 5687 - 5703
• Main Authors: Zhang, Chongyuan, Lin, Weiren, He, Manchao, Tao, Zhigang, Meng, Wen
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.09.2022; Springer Nature B.V
• Subjects: Anelasticity; Boreholes; Civil Engineering; Coastal zone; Compressive properties; Cores; Crack propagation; Earth and Environmental Science; Earth Sciences; Earthquakes; Fracture mechanics; Geological faults; Geophysics/Geodesy; Geothermal resources; Original Paper; Palaeomagnetism; Paleomagnetism; Recovery; Resource development; Rock; Rock mechanics; Rocks; Seismic activity; Seismicity; Strain; Stress; Stress distribution; Stress propagation; Stress state; Stress tensors; Subduction; Subduction (geology); Tensors; Philippine Sea; China; Coastal region of Southeastern China (CRSC); Anelastic strain recovery; In-situ stress; Extensional stress state; Geothermal exploration
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-022-02915-7

The in-situ stress state in the shallow crust of the coastal region of Southeastern China (CRSC) remains poorly understood. We conducted anelastic strain recovery measurements in a 2 km deep geothermal borehole to investigate the in-situ stress state. Four high-quality granite core samples were employed to successfully estimate the full stress tensors. The results show that the maximum principal stress σ 1 is nearly vertical, implying an extensional shallow crust that is controlled by normal faulting. From ~1865 to ~1959 m in depth, the maximum and minimum horizontal principal stresses ( S Hmax and S hmin ) are 36.1–48.7 MPa and 34.0–38.5 MPa, respectively. Based on the paleomagnetic analysis, the orientation of the maximum horizontal compressive stress S Hmax is determined as N43° ± 19°W and aligned with the subduction direction of the Philippine Sea plate. According to the compiled stress data, the S Hmax orientations in the CRSC rotate counterclockwise towards the Chinese mainland, which are consistent with those of the earthquake focal mechanisms and regardless of earthquake type, indicating a heterogeneous stress field dominancy in the CRSC. Our findings manifest that there is a lower horizontal compressive stress state in the upper crust in the study region. We also discussed the possible influence of in-situ stress on wellbore stability and fracture propagation in hot dry rock exploration and further quantitatively analyzed the reactivation possibility of natural fractures under different injection pressures. This study will provide scientific data for geodynamic research, fault seismicity, and geothermal development in the region in the future. Highlights We used the anelastic strain recovery (ASR) method to obtain the in-situ stress state at 2 km depth in Xiamen, Fujian, China, indicating that Xiamen is controlled by normal-faulting stress. In ASR experiments, rock mechanics and rock compliance experiments were conducted to help better constrain the in-situ stress state. The collision of the Eurasian and Philippine Sea plates controls shallow crustal stress pattern and shows a relatively low horizontal compressive stress state in the coastal region of Southeastern China. Implications of in-situ stresses on geothermal resource development were discussed and quantitatively analyzed.