10+ years continuous downhole pore pressure record from the decollement zone at Nankai Trough off Muroto

Masataka Kinoshita, Keir Becker, Earl E. Davis

Research output: Contribution to conferencePaper

Abstract

Since 2001, borehole pore pressure data have been continuously logged near the toe of Nankai accretionary prism off Muroto, by usingtwo 'ACORK'borehole observatories installed during the Ocean Drilling Program (ODP) Leg 196. Pore pressure are recorded at multiple intervals from the seafloor to the plate interface. Data have been retrieved once every year using the Remotely-Operated Vehicle KAIKOor manned submersibleShinkai 6500of JAMSTEC. We now have over 10-year-long continuous pressure records, and present here a preliminary data. The overpressure of up to 100 kPa was observed just above the décollementzone, although the reliability of the pressure data there is yet to be tested in the future. Pressure oscilationsfrom multiple depths,corresponding to the tidal modulations,show systematic decrease with increasing depth.Transient changes were observed at the time of several earthquakes, including a swarm of very-low-frequency events (VLFE) in 2003 and 2004.We believe that continuous pressure data can make an essential reference to the possible pressure anomalies prior to the near-future great subduction zone earthquake.

Original languageEnglish (US)
StatePublished - Jan 1 2012
Event18th Formation Evaluation Symposium of Japan 2012 - Chiba, Japan
Duration: Sep 27 2012Sep 28 2012

Other

Other18th Formation Evaluation Symposium of Japan 2012
CountryJapan
CityChiba
Period9/27/129/28/12

ASJC Scopus subject areas

  • Economic Geology
  • Geochemistry and Petrology
  • Geology
  • Geotechnical Engineering and Engineering Geology
  • Energy Engineering and Power Technology

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    Kinoshita, M., Becker, K., & Davis, E. E. (2012). 10+ years continuous downhole pore pressure record from the decollement zone at Nankai Trough off Muroto. Paper presented at 18th Formation Evaluation Symposium of Japan 2012, Chiba, Japan.