Hosokawa Takahiro, Hashimoto Yoshitaka
Department of Global Environment and Disaster Prevention, Faculty of Science and Technology, Kochi University, Akebonocho 2-5-1, Kochi, 780-8520, Japan.
Sci Rep. 2022 Aug 30;12(1):14789. doi: 10.1038/s41598-022-19083-x.
Fluid pressure along faults plays a significant role in fault behaviors in seismic cycles in subduction zones. When a thermal pressurization event occurs, the fluid pressure rises; conversely, when a fault-valve behavior event occurs, the fluid pressure falls. The stress state changes with seismic cycles from a reverse fault regime to a normal fault regime, as observed in both geophysical observations and geological records. Fluid pressure has been estimated for both modern accretionary prisms and exhumed accretionary complexes. However, changes in fluid pressure on seismogenic faults have not been connected to seismic cycles. Here, we quantitatively show the dynamic change in fluid pressure in a seismogenic fault with geological evidence from an exhumed accretionary complex. We found extensional veins related to seismogenic fault records that exchanged stress states the during seismic cycles. We also constrained the fluid pressure quantitatively, both at an increasing stage during an event and at a decreasing stage after an event. In this procedure, we propose new methods to constrain the magnitude of vertical stress and rock tensile strength.
俯冲带地震周期中断层的流体压力对断层活动起着重要作用。当发生热增压事件时，流体压力升高；相反，当发生断层阀行为事件时，流体压力下降。正如在地球物理观测和地质记录中所观察到的，应力状态随地震周期从逆断层状态转变为正断层状态。现代增生楔体和出露的增生杂岩的流体压力都已得到估算。然而，发震断层上流体压力的变化尚未与地震周期联系起来。在此，我们利用一个出露的增生杂岩的地质证据，定量展示了发震断层中流体压力的动态变化。我们发现了与发震断层记录相关的张性脉体，它们在地震周期中交换了应力状态。我们还定量地约束了事件期间压力增加阶段和事件后压力下降阶段的流体压力。在此过程中，我们提出了新的方法来约束垂直应力的大小和岩石抗拉强度。
