在地震滑移速率下，含水斷層帶會因滑動而產生大量摩擦熱，其導致的高溫，可能引發熱相關物理化學過程，並影響材料的滑移行為，同時孔隙水壓也會因此過程，持續受影響而變化，繼而改變斷層的摩擦強度。因此了解溫度和孔隙水壓動態演化將對深入了解斷層的摩擦行為相當有幫助。本研究結合高速旋剪實驗的剪應力數據和微觀構造觀察之證據 (如黏土礦物的熱崩解)，並以實驗過程量測的溫度作為制約，建立耦合熱水力化的溫度與孔隙水壓數值模型，探討滑移過程的動態弱化機制。同時研究究與過去發展的模型比較，透過熱源幾何設定和重新界定吸熱作用的發生範圍，改善了過去模型有初期溫度低估和後期摩擦面異常高溫等現象。本研究模擬顯示，在高嶺土、伊萊石和石英混合的斷層泥為材料的高速實驗中，不排水條件下摩擦熱引發孔隙水壓在滑移初期迅速飆升，熱增壓作用極為顯著，主導了斷層的急遽弱化。在排水條件下，滑動開始後4秒，可能水的逸散而導致樣品變得乾燥，有較劇烈碰撞形成細小顆粒，並引發顆粒流產生，主導後期弱化。滑移過程中溫度、孔隙水壓與礦物化學作用、水的相態變化等存在著強烈關聯，顯示了多物理場耦合模擬對於評估動態弱化機制與斷層穩定性具有重要性。;Under earthquake slip rates， a large amount of frictional heat can be generated along the localized slip plane in a saturated fault zone. The high temperature (T) and thermal-physicochemical processes affect the slip behaviors. At the same time， pore fluid pressure (Pf) changes during this process， which also varies the fault strength. Therefore， understanding the dynamic evolution of T and Pf is helpful for understanding the frictional behavior of faults. By combining the mechanical data and microstructure observations from high-velocity rotary shear experiments in Nguyen et al. (In revision)， this study built a numerical model. This model couples thermal-hydro-mechanical-chemical (THMC) processes and uses measured temperature as a constraint to help understand the dynamic weakening mechanism. Compared with previous models， we improved the underestimation of initial T and the abnormally high T on the slip surface in the later stage by adjusting the heat source geometry and redefining the zone of endothermic reactions. Also， by coupling the axial displacement data， we tried to add the effect of the axial strain for Pf. For the ternary minerals， under undrained conditions， the rapid rise in Pf caused by frictional heat is significant. Thermal pressurization is the main mechanism triggers the rapid weakening of the fault. Under drained condition， at 4 s of the slip， the sample may become dry due to the drainage of water， resulting in more grain crushing and comminution that form fine grains and trigger granular flow， which dominates the weakening in the later stage. The significant relationships among T， Pf ， thermal decomposition of clay minerals， and water phase changes during the slip show the importance of multiphysics coupling simulations in evaluating dynamic weakening mechanisms and fault stability.
