Bangs, Nathan L.; Shipley, Thomas H.; Gulick, Sean P. S.; Moore, Gregory F.; Kuromoto, Shinichi; Nakamura, Yasuyuki (2004): Evolution of the Nankai Trough decollement from the trench into the seismogenic zone; inferences from three-dimensional seismic reflection imaging. Geological Society of America (GSA), Boulder, CO, United States, Geology (Boulder), 32 (4), 273-276, georefid:2004-060769
Abstract:
We mapped the amplitude of the Nankai Trough subduction thrust seismic reflection from the trench into the seismogenic zone with three-dimensional seismic reflection data. The decollement thrust forms within the lithologically homogeneous Lower Shikoku Basin facies along an initially nonreflective interface. The reflection develops from a porosity contrast between accreted and underthrust sedimentary material because of accretionary wedge consolidation and rapid loading and delayed consolidation of the underthrust section. A decollement-amplitude map shows a significant decline from high amplitudes at the trench to barely detectable levels 25-30 km landward. Three other observations coincide with the amplitude decline: (1) the decollement initially steps down to deeper stratigraphic levels, (2) the wedge taper increases dramatically, and (3) the thrust becomes seismogenic. The amplitude decline and the coincident decollement and accretionary-edge tectonic and seismogenic behavior are attributed to the loss of fluids and potentially loss of excess fluid pressures downdip along the subduction thrust.
Coverage:
West: 133.0000 East: 135.3000 North: 34.0000 South: 32.0000
Relations:
Supplemental Information:
Univ. Texas, Inst. Geophys., Contrib. No. 1680
Data access: