Tectonics, Fluids, and the Seismogenic Zone: Four Decades of Drilling at Convergent Margins (Invited)
Abstract
Investigations of Tectonics, Fluids, and the Seismogenic Zone are three disciplines that have driven convergent margin drilling. Each of these major themes sequentially evolved as centerpieces of drilling as the intellectual framework and the requisite technologies developed. Each remains active today. In the 1970s and early 1980s, initial results from testing plate tectonic theory defined the nature of progressive accretion, and conversely, tectonic erosion at convergent margins. With the more robust D/V JOIDES Resolution, investigation of fluid pressure, compositions, migration paths, and sediment/rock permeability became possible. 3D seismic data, first available in the early 1990s, detailed fluid migration paths inferred from porewater geochemical anomalies, emphasizing the importance of faults as fluid conduits. 3D seismic volumes also resulted in extraordinary insights on the structure and tectonics of convergent margins. In the mid 1990s packer testing and long-term monitoring of fault zones provided the first estimates of in situ fluid pressures, permeabilities, and variation of the latter with effective stress. Experimental studies, and hydrological and geomechanical modeling have provided critical perspectives on the observational data. During the late 1990s and 2000s the convergent margin community focused on earthquake processes in the Seismogenic Zone Experiment (SEIZE). Understanding of tectonics and fluids, plus monitoring, 3D seismic imaging, Logging While Drilling technology, and D/V Chikyu riser drilling capability have all contributed to emergent accomplishments of SEIZE. Some key results of this program include 1) estimates of material flux into the seismogenic zone, 2) measurement of stress orientation and magnitude across the margin of SW Japan, 3) recognition of high velocity fault slip at shallow depths, 4) correlation of monitored variations in fluid pressure and composition with seismic events, and 5) the initiation of a deep riser hole. Currently the SEIZE program across SW Japan is the best active margin transect ever. Completion of the deep riser hole and associated monitoring will make this effort truly transformative.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.U42A..03M
- Keywords:
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- 3060 MARINE GEOLOGY AND GEOPHYSICS / Subduction zone processes;
- 7240 SEISMOLOGY / Subduction zones