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Episodic seafloor mud brecciation due to great subduction zone earthquakes

Arito Sakaguchi, Gaku Kimura, Michael Strasser, Elizabeth J. Screaton, Daniel Curewitz and Masafumi Murayama
Episodic seafloor mud brecciation due to great subduction zone earthquakes
Geology (Boulder) (October 2011) 39 (10): 919-922


The Nankai Trough off southwest Japan has an approximately 1300 yr historical record of great earthquakes, including the most recent, the A.D. 1944 Tonankai (M = 8.2) earthquake. Evaluation of the activity of an individual submarine fault is difficult when only onland observations are available. Submarine core records can pinpoint individual fault activity. Here we present Integrated Ocean Drilling Program (IODP) Nankai Trough Seismogenic Zone Experiment data from the shallow portion. IODP Expedition 316 drilled and cored several holes in the shallow portion of the offshore Tonankai earthquake area, including sites in the hanging wall of a margin-dominating splay fault that has previously been interpreted to have ruptured coseismically during megathrust earthquakes. X-ray computed tomography scanning revealed that the uppermost core at one site contains repeated occurrences of mud breccia. Radioisotope dating of the uppermost mud breccia indicates a deposition time consistent with the 1944 Tonankai earthquake, suggesting that the mud-breccia layers result from episodic brecciation caused by seismic shaking. Mud brecciation provides a potential new tool to reconstruct ancient earthquake history in subduction zones.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 39
Serial Issue: 10
Title: Episodic seafloor mud brecciation due to great subduction zone earthquakes
Affiliation: JAMSTEC (Japan Agency for Marine-Earth Science and Technology), IFREE (Institute for Frontier Research on Earth Evolution), Yokohama, Japan
Pages: 919-922
Published: 201110
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 36
Accession Number: 2011-097142
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. sects., sketch maps
N33°01'00" - N33°13'60", E136°43'00" - E136°48'00"
Secondary Affiliation: University of Tokyo, JPN, JapanUniversity of Bremen, DEU, GermanyUniversity of Florida, USA, United StatesSyracuse University, USA, United StatesKochi University, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201150
Program Name: IODPIntegrated Ocean Drilling Program
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