Geomorphological study on a clastic accretionary prism: The Nankai Trough

Okino, Kyoko; Kato, Y.

doi:10.1111/j.1440-1738.1995.tb00142.x

Cited by 28 publications

(11 citation statements)

References 27 publications

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“…The thermally controlled interseismic locked zone of Hyndman et al (1995) defines the updip limit of the aseismic-to-seismic transition as coinciding with the 150 ЊC isotherm, which is shallow along the Muroto transect because of the young (ca. 16 Ma) age of the subducting oceanic crust (Okino and Kato, 1995). The interseismic locked zone extends updip 4 km subseafloor and ϳ35 km landward from the trench, coincident with the updip extent of microseismicity.…”

Section: Aseismic-to-seismic Transition Off Southeast Shikokumentioning

confidence: 97%

Evolution of the Nankai Trough décollement from the trench into the seismogenic zone: Inferences from three-dimensional seismic reflection imaging

Bangs

Shipley

Gulick

et al. 2004

Geol

131

112

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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 décollement 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 décollement-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 décollement 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 décollement and accretionarywedge tectonic and seismogenic behavior are attributed to the loss of fluids and potentially loss of excess fluid pressures downdip along the subduction thrust.

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Section: Aseismic-to-seismic Transition Off Southeast Shikokumentioning

confidence: 97%

Evolution of the Nankai Trough décollement from the trench into the seismogenic zone: Inferences from three-dimensional seismic reflection imaging

Bangs

Shipley

Gulick

et al. 2004

Geol

131

112

View full text Add to dashboard Cite

show abstract

“…In deeper water, a fault-controlled ridge-and-trough landscape characterizes the frontal accretionary prism (Ashi & Taira 1992;Okino & Kato 1995). Two ODP sites (1175 and 1176) penetrated one of the small 'piggyback' basins on the lower slope (Fig.…”

Section: Tectonic and Stratigraphic Settingmentioning

confidence: 99%

Late Cenozoic evolution of the Nankai trench-slope system: evidence from sand petrography and clay mineralogy

Underwood

Fergusson

2005

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Submarine slope systems in subduction zones evolve in response to a combination of tectonic and sedimentary forcing. It can be difficult to determine how and when tectonic forcing affects sedimentation, especially when investigating ancient rock successions, but one of the more reliable indicators is a change in sediment composition. During Leg 190 of the Ocean Drilling Program, sandy turbidites were recovered from a Quaternary trench wedge (Nankai Trough), a Pliocene-Pleistocene slope basin, the underlying Pliocene-Miocene accretionary prism, and a Miocene turbidite facies in the Shikoku Basin. Differences in detrital provenance between the sand and clay-sized fractions indicate that turbidity currents did not follow pathways of suspended-sediment transport during the past 10 Ma. During the middle and late Miocene, the sand probably was eroded from a newly exposed accretionary complex (Shimanto Belt). In contrast, high contents of detrital smectite in Miocene mudstones (> 50 wt% of the <2 fxm size fraction, relative to illite, chlorite + kaolinite, and quartz) point to a strong volcanic component of suspended-sediment input (Izu-Bonin island arc). The sand in accreted Pliocene turbidites was also eroded from the Shimanto Belt and transported by transverse flow down the insular slope. The trench-wedge facies then switched to axial flow during the Quaternary, when the sand supply tapped a mixed volcanicmetasedimentary provenance in the rapidly uplifted Izu-Honshu collision zone. Progressive depletion of smectite during the Pliocene and Pleistocene (<20 wt%) points to increased movement of illite-and chlorite-rich clay toward the east and NE from sources on Kyushu and Shikoku. That shift in mud composition coincides with intensification of the North Pacific western boundary current (Kuroshio Current) at approximately 3 Ma. Overall, the depositional system in the Nankai Trough and Shikoku Basin shifted its sand sources because of regional tectonics, whereas the suspendedsediment budget was modulated by hemispheric changes in ocean-water circulation.

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“…The slip on the thrust below this ridge may indicate shortening of the oceanic plate in this region (e.g., Mazzotti et al 2002). Northwest of this ridge, seafloor morphologic data (Lallemand et al 1992;Okino and Kato 1995) and geomagnetic data (Le Pichon et al 1996) show a structure below the Kumano forearc basin that represents a subducting seamount. This seamount is part of the Paleo-Zenisu ridge, which was also formed by a chain of seamounts that is almost parallel to the trough axis, 20-30 km wide, about 200 km long, and with a maximum height of 2.5 km.…”

Section: Introductionmentioning

confidence: 99%

Seismic activity beneath the Nankai trough revealed by DONET ocean-bottom observations

2013

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We conducted a detailed investigation of seismic activity from January 2011 to February 2013 along the Nankai trough off the Kii Peninsula, central Japan, by using data obtained from the DONET ocean-bottom observation network. The hypocenters are mostly within the subducting Philippine Sea (PHS) plate, although a few are along the plate boundary or in the sedimentary wedge below the Kumano forearc basin. The seismic activity can be separated into events above and below 20 km depth, which corresponds approximately to the Moho. The hypocenter distributions are distinctly different for these groups. The seismic activity in the oceanic crust can be further separated into three clusters. Most of the seismic activity recorded in our data represents aftershocks of the 2004 off the Kii Peninsula earthquakes (M JMA = 7.1, 7.4, and 6.5), which occurred in the PHS plate. The hypocenter distribution in the oceanic crust correlates well with the location of the Paleo-Zenisu ridge, which is formed by a chain of seamounts that is subducting beneath the forearc basin. The hypocenters in the uppermost mantle are aligned on a plane dipping to the southeast, consistent with the existence of a thrust fault cutting through the lithosphere of the oceanic plate. The focal mechanisms of the earthquakes show that the axis of compressive stress in the PHS plate is oriented N-S, almost perpendicular to the direction of plate convergence, indicating a complex tectonic regime in this region. These results suggest that intraplate shortening may be occurring in the subducting oceanic plate.

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Geomorphological study on a clastic accretionary prism: The Nankai Trough

Cited by 28 publications

References 27 publications

Evolution of the Nankai Trough décollement from the trench into the seismogenic zone: Inferences from three-dimensional seismic reflection imaging

Evolution of the Nankai Trough décollement from the trench into the seismogenic zone: Inferences from three-dimensional seismic reflection imaging

Late Cenozoic evolution of the Nankai trench-slope system: evidence from sand petrography and clay mineralogy

Seismic activity beneath the Nankai trough revealed by DONET ocean-bottom observations

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