IODP Expedition 405 drilled the Japan Trench subduction fault in autumn 2024 to investigate its hydraulic structure following the 2011 Tohoku-Oki earthquake. Initial results indicated that the fault rocks may have re-cemented, limiting fluid movement and potentially storing energy for future seismic events. This research enhances understanding of fluid dynamics within faults, contributing to tsunami-earthquake preparedness efforts.
In autumn 2024, the International Ocean Discovery Program (IODP) Expedition 405 undertook drilling operations at the Japan Trench subduction fault to examine the hydraulic structure of this significant geological feature. This study was driven by the devastating impacts of the 2011 Tohoku-Oki earthquake and the resultant tsunami, which reached heights of 40 meters and demonstrated the unpredictability of subduction zone behavior. Initial findings suggest that the fault rocks, affected by the earthquake, may have primarily re-cemented, impeding fluid movement and potentially storing mechanical energy—a characteristic that could amplify the magnitude of future seismic events. Consequently, insights from this expedition aim to improve our understanding of the role of fluids in fault healing and the seismic cycle, enhancing preparedness for subsequent tsunami-generating earthquakes.
The 2011 Tohoku-Oki earthquake, classified as a magnitude 9.0 event, was unprecedented in scale and led to significant tsunamis impacting Japan’s northeast coast. This disaster underscored the limitations in current scientific understanding regarding the mechanical dynamics of subduction zone earthquakes, particularly in terms of fault slip and fluid dynamics. Current research indicates that post-earthquake fluid pressure can increase slip along faults, yet direct examination of these deep-seated faults has been limited due to their inaccessibility. Through deep-ocean drilling, scientists at IODP Expedition 405 sought to recover valuable data on these elusive structures, particularly their hydraulic conditions years after the catastrophic event.
The findings from IODP Expedition 405 present a pivotal step in understanding the hydraulic environment of subduction faults, particularly in relation to fault healing mechanisms. The potential for re-cementation of fault rocks to inhibit fluid flow raises critical questions about the storage of energy and the conditions leading to future earthquakes. This research not only aims to deepen the scientific community’s comprehension of fault dynamics but also serves as a foundational approach in formulating strategies to mitigate the risks associated with underwater seismic activity and ensuing tsunamis.
Original Source: www.nature.com
