Into the deep: Insights and challenges associated with subduction zone drilling
Tamara Jeppson
Earthquake Science Center, USGS
- Date & Time
- Location
- Online-only seminar via Microsoft Teams
- Summary
The largest magnitude earthquakes we have observed occur along subduction zone thrust faults. However, the subseafloor location of these faults makes them incredible difficult to study. One useful method for studying these zones is scientific ocean drilling, which has helped to characterize the structure, composition, physical properties, role of fluids, temperature, and stress state in subduction zones. We discuss some of the challenges that faced the recent IODP Expedition 358’s quest to drill the deep megathrust fault at the Nankai Trough and lessons learned in the process.
Previous subduction zone drilling has focused on the relatively shallow part of the subduction zone, ~ 1 km below the seafloor. IODP Expedition 358 was the first attempt to drill into a subduction zone fault at seismogenic depths. The expedition occurred over 167 days and attempted to extend existing IODP Hole C0002P by over 2 km to reach a depth of ~ 5200 mbsf. Multiple operational challenges prevented this goal from being accomplished. However, borehole did reach 3262.5 mbsf making it the deepest scientific ocean drilling hole to date. The lessons learned from Expedition 358 could be useful for planning future deep drilling projects.
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