georefid:2004-060769SEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.1130/G20211.2<gco:CharacterString>Evolution of the Nankai Trough decollement from the trench into the seismogenic zone; inferences from three-dimensional seismic reflection imaging</gco:CharacterString>2004-01-01publicationgeorefid:2004-060769doi:10.1130/G20211.2Bangs, Nathan L.University of Texas, Institute for Geophysics, Austin, TX, United StatesauthorShipley, Thomas H.University of Hawaii at Manoa, United StatesauthorGulick, Sean P. S.Japan Marine Science and Technology Center, JapanauthorMoore, Gregory F.University of Tokyo, JapanauthorKuromoto, ShinichiauthorNakamura, YasuyukiauthorGeological Society of America (GSA), Boulder, CO, United StatespublisherdocumentHardcopyGeology (Boulder)32 (4)273-276We 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.completedSolid-earth geophysicsApplied geophysicsaccretionary wedgesdecollementearthquakesfaultsfluid pressuregeophysical methodsgeophysical profilesgeophysical surveysLeg 196mappingmarine sedimentsNankai TroughNorth PacificNorthwest PacificOcean Drilling Programocean floorsPacific Oceanplate tectonicspore waterporosityreflection methodssedimentsseismic methodsseismic profilesseismicityShikoku Basinsubductionsubduction zonessurveystrenchesunderthrust faultsWest Pacificurn:org.iodp:exp:196urnlargerWorkCitationcampaignEnglishgeoscientificInformation133.0000135.300032.000034.0000Univ. Texas, Inst. Geophys., Contrib. No. 1680