Targeted 3‐D prestack depth imaging at Legs 190‐196 ODP drill sites (Nankai Trough, Japan)

Pisani, P. Costa; Reshef, Moshe; Moore, Gregory F.

doi:10.1029/2005gl024191

Cited by 23 publications

(34 citation statements)

References 18 publications

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“…For several margins, it has been suggested that at the onset of subduction, the décollement preferentially localizes in weak strata (e.g., Moore, 1989;Deng and Underwood, 2001;Kopf and Brown, 2003). This is inferred from mechanical data, and often corroborated by seismic reflection data in which the plate boundary proto-décol-lement can be correlated with negative-polarity reflectors in the incoming sequence (e.g., MacKay, 1995;Moore et al, 1995Moore et al, , 1998Costa Pisani et al, 2005).…”

Section: Introductionmentioning

confidence: 67%

Lithologic control of frictional strength variations in subduction zone sediment inputs

et al. 2018

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At convergent margins, marine sediments deposited seaward of the subduction zone forearc on the incoming plate (the "subduction inputs") represent the initial condition for geomechanical processes during subduction. The frictional strength of these sediments is a key parameter governing deformation during subduction, which is controlled to first order by lithologic composition. We combine here the results of laboratory friction experiments and quantification of mineral assemblage for scientific drilling samples recovered from three particularly well-studied subduction zones: the Nankai Trough (southwestern Japan), the Japan Trench (northeastern Japan), and Costa Rica. In the Japan Trench, frictionally weak smectite-rich pelagic clay contrasts sharply with stronger, more siliceous hemipelagic material. This strength contrast dictates the stratigraphic position of initial plate boundary formation and influences slip behavior of the shallow megathrust. In the Costa Rica subduction zone, relatively weak clay-rich hemipelagic sediment overlies frictionally strong pelagic nannofossil oozes and chalks, which could be a factor for the development of features such as a small amount of offscraping near the toe and subduction erosion where ooze or chalk dominates. In the Nankai Trough, however, a wide range of frictional strength values is observed that does not correlate with clay mineral content. In this case, mechanical behavior at Nankai is likely influenced by other factors related to diagenesis or fluid overpressuring.

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Section: Introductionmentioning

confidence: 67%

Lithologic control of frictional strength variations in subduction zone sediment inputs

et al. 2018

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“…Because of the great water depths (>6,000 m), the water velocity (which does not vary greatly) has a large effect on the migrations. We estimate that within the sediment section, which is less than 1,000-mthick, our velocity errors are no more than approximately 200 to 400 m s −1 based on PSDM sediment velocity sensitivity in the high-resolution lines (e.g., Tsuru et al 2000;Costa Pisani et al 2005). Such velocity errors would result in a maximum of approximately 5% to 10% error in depth that would not affect our structural interpretations.…”

Section: Methodsmentioning

confidence: 91%

Outer-rise normal fault development and influence on near-trench décollement propagation along the Japan Trench, off Tohoku

Boston

Moore

Nakamura

et al. 2014

Earth, Planets and Space

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Multichannel seismic reflection lines image the subducting Pacific Plate to approximately 75 km seaward of the Japan Trench and document the incoming plate sediment, faults, and deformation front near the 2011 Tohoku earthquake epicenter. Sediment thickness of the incoming plate varies from <50 to >600 m with evidence of slumping near normal faults. We find recent sediment deposits in normal fault footwalls and topographic lows. We studied the development of two different classes of normal faults: faults that offset the igneous basement and faults restricted to the sediment section. Faults that cut the basement seaward of the Japan Trench also offset the seafloor and are therefore able to be well characterized from multiple bathymetric surveys. Images of 199 basement-cutting faults reveal an average throw of approximately 120 m and average fault spacing of approximately 2 km. Faults within the sediment column are poorly documented and exhibit offsets of approximately 20 m, with densely spaced populations near the trench axis. Regional seismic lines show lateral variations in location of the Japan Trench deformation front throughout the region, documenting the incoming plate's influence on the deformation front's location. Where horst blocks are carried into the trench, seaward propagation of the deformation front is diminished compared to areas where a graben has entered the trench. We propose that the décollement's propagation into the trench graben may be influenced by local stress changes or displacements due to subduction of active normal faults. The location and geometry of the up-dip décollement at the Japan Trench is potentially controlled by the incoming outer-rise faults.

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“…About 200 km north of the Muroto Transect, NanTroSEIZE established 13 drilling sites along the Kumano Transect off the Kii Peninsula where the plate boundary fault system is within reach of the Chikyu's riser drilling technology. In the course of numerous seismic and bathymetric surveys, the structure of the Nankai Trough off Shikoku was imaged extensively (e.g., Aoki et al, 1982;Ashi and Taira, 1992;Costa Pisani et al, 2005;Kodaira et al, 2000;Le Pichon et al, 1987;Moore et al, 1990Moore et al, , 1991Okino and Kato, 1995;Park et al, 1999Park et al, , 2000Stoffa et al, 1992;Taira and Ashi, 1993). A large volume of 3-D seismic reflection data was acquired in 1999 (R/V Ewing Cruise 9907/8) in an effort to image the décollement from the trench into the seismogenic zone (e.g., Bangs et al, 1999Bangs et al, , 2004Bangs and Gulick, 2005;Gulick et al, 2004).…”

Section: Geological Settingmentioning

confidence: 99%

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2017

Proceedings of the International Ocean Discovery Program

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International Ocean Discovery Program (IODP) Expedition 370 explored the limits of the biosphere in the deep subseafloor where temperature exceeds the known temperature maximum of microbial life (~120°C) at the sediment/basement interface ~1.2 km below the seafloor. Site C0023 is located in the protothrust zone in the Nankai Trough off Cape Muroto at a water depth of 4776 m, in the vicinity of Ocean Drilling Program (ODP) Sites 808 and 1174. In 2000, ODP Leg 190 revealed the presence of microbial cells at Site 1174 to a depth of ~600 meters below seafloor (mbsf ), which corresponds to an estimated temperature of ~70°C, and reliably identified a single zone of elevated cell concentrations just above the décollement at around 800 mbsf, where temperature presumably reached 90°C; no cell count data was reported for other sediment layers in the 70°-120°C range because the detection limit of manual cell counting for low-biomass samples was not low enough. With the establishment of Site C0023, we aimed to detect and investigate the presence or absence of life and biological processes at the biotic-abiotic transition utilizing unprecedented analytical sensitivity and precision. Expedition 370 was the first expedition dedicated to subseafloor microbiology that achieved time-critical processing and analyses of deep biosphere samples, conducting simultaneous shipboard and shore-based investigations.Our primary objective during Expedition 370 was to study the relationship between the deep subseafloor biosphere and temperature. We comprehensively studied the controls on biomass, activity, and diversity of microbial communities in a subseafloor environment where temperatures increase from ~2°C at the seafloor tõ 120°C and thus likely encompasses the biotic-abiotic transition zone. This included investigating whether the supply of fluids containing thermogenic and/or geogenic nutrient and energy substrates may support subseafloor microbial communities in the Nankai accretionary complex. To address these primary scientific objectives and questions, we penetrated 1180 m and recovered 112 cores of sediment and across the sediment/basalt interface. More than 13,000 samples were collected, and selected samples were transferred to the Kochi Core Center by helicopter for simultaneous microbiological sampling and analysis in laboratories with a superclean environment. In addition to microbiological measurements, we determined the geochemical, geophysical, and hydrogeological characteristics of the sediment and the underlying basement and installed a 13-thermistor sensor borehole temperature observatory into the borehole at Site C0023.

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Targeted 3‐D prestack depth imaging at Legs 190‐196 ODP drill sites (Nankai Trough, Japan)

Cited by 23 publications

References 18 publications

Lithologic control of frictional strength variations in subduction zone sediment inputs

Lithologic control of frictional strength variations in subduction zone sediment inputs

Outer-rise normal fault development and influence on near-trench décollement propagation along the Japan Trench, off Tohoku

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