[S-IT20] New perspectives on accretion and exhumation processes during oblique plate convergence

[SIT20-12] Influences of Stress Variation on the Evolution of 3D Fracture System: An Example in NE Taiwan

*En-Chao Yeh¹、Huong Pham¹、Ping-Chuan Chen¹、Yu-Chang Chan²、Chih-Hsiang Yeh³、Kuo-Jen Chang³、Yu-Chung Hsieh⁴ (1.Department of Earth Sciences, National Taiwan Normal University, Taipei, Taiwan、2.Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan、3.Department of Civil Engineering, National Central University, Taoyuan, Taiwan、4.Central Geological Survey, MOEA, Taipei, Taiwan)

キーワード：Fracture Instability, 3D Fracture System, Stress Variation, NE Taiwan

Fractures can be nucleated and/or reactivated by appropriated stress state. It is well established that NE Taiwan has been experienced the tectonic evolution from oblique collision to backarc extension in the view of stress variation during late Cenozoic. In this study, we aim to verify whether fractures in NE Taiwan can be manipulated by the stress change along the NE coastline of Taiwan.
3D fracture maps and stress state are two essential elements in this experiment. We recognized 120 of 187 reliable fractures based on DEM analysis and interpretation and further calculated their attitudes. Stress inversion was conducted from focal mechanism data of 1991 to 2016. Inferred stress state can be divided into 3 domains with 12 cells from north to south. After evaluating the fracture instabilities with corresponded stress path, it is realized that surface fractures in DEM could be nucleated with the applied stress field in the evolution of the tectonic setting from the south to the north along the coastline area at NE Taiwan. We also examined the slip tendency to explore the reactivation tendency of nucleated surface fractures. The results confirmed the important role of the back-arc extension of Okinawa Trough opening to reactivate surface fractures in NE Taiwan. Therefore, correlation between 3D fracture map and stress state can afford vital applications in terms of the landslide, groundwater, site characteristics and scientific research issues.