Subduction Zones: Structure and Deformation History

摘要: Abstract In the first decade of Integrated Ocean Drilling Program (IODP) 2003–2013, drilling expeditions in Nankai Trough Kumano transect, Costa Rica Osa Peninsula and Japan Trench provided great insights into deformation processes subduction zone forearcs. pursuit IODP's objective investigating onset seismogenic locking rupture, overarching aim all these transects was to drill plate boundary fault systems, both at shallow, presumed aseismic levels greater, depths study faults their immediate environment. Closely allied objectives included determination ages tectonic stratigraphic events marginal wedges, elucidation hydrogeologic diagenetic active margins, monitoring stress conditions seismic activity. Taken together, important results from this work include following: (1) Rapid localized slip can sometimes extend way trench even where hosted porous, poorly consolidated marine sediments. This may be due frictional properties shallow material; (2) Sediment supply high erosive accretionary as recorded by sedimentation rates forearc basins, but locus timing versus forearc/slope basin settings profoundly impact wedge evolution; (3) Observed principal orientations are governed convergence relative magnitudes exhibit a more complex relationship with tectonics than previously anticipated; (4) Strong fluid overpressures not observed upper mid-wedge although reflection data suggest that elevated pore pressure play an role strength depth. Finally, long-term borehole observatories installed steps toward goal systems over time.