Sediment provenance and controls on slip propagation; lessons learned from the 2011 Tohoku and other great earthquakes of the subducting northwest Pacific Plate

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doi: 10.1130/GES01099.1
Author(s): Moore, J. Casey; Plank, Terry A.; Chester, Frederick M.; Polissar, Pratigya J.; Savage, Heather M.
Author Affiliation(s): Primary:
University of California, Santa Cruz, Earth and Planetary Sciences, Santa Cruz, CA, United States
Lamont-Doherty Earth Observatory, United States
Texas A&M University, United States
Volume Title: Geosphere (Boulder, CO)
Source: Geosphere (Boulder, CO), 11(3), p.533-541. Publisher: Geological Society of America, Boulder, CO, United States. ISSN: 1553-040X
Note: In English. 43 refs.; illus., incl. sketch maps
Summary: The ∼50 m slip of the Tohoku earthquake occurred along a very fine grained red-brown smectitic clay horizon subducting in the Japan Trench. This clay, cored in the plate boundary fault at Integrated Ocean Drilling Program Expedition 345, Site C0019, correlates with similar pelagic clay recovered seaward of the trench at Deep Sea Drilling Project Sites 436 and 1149. Comparable clays occur throughout the northwest Pacific Basin. Backtracking of ocean drilling Sites 436, C0019, and 1149 indicates that they formed during the Early Cretaceous at the Kula-Pacific Ridge. These sites traveled northwestward through the equatorial zone, accumulating siliceous and calcareous oozes until ca. 100∼85 Ma. Sites 436, C0019, and 1149 then entered the realm of pelagic clay deposition where they remained until ca. 15 Ma. From ca. 15 Ma to the present, Sites 436, C0019, and 1149 accumulated clays and silty clays with variable amounts of siliceous microfossils and volcanic ash, representing the transition from deep-sea conditions to a continental margin sedimentary environment. The predicted backtracked vertical sequence of sediments fits well with the cores at Sites 436, 1149, and C0019, after accounting for structural complications in the latter.Pelagic clay occurs in numerous boreholes penetrating the relatively smooth ocean floor of the Pacific plate north and northeast of the Tohoku earthquake. Here the widespread pelagic clay apparently fosters tsunami and tsunamigenic earthquakes. Seamounts rising above the normal oceanic crust accumulated sequences of calcareous sediments as their crests remained above the calcite compensation depth for most of their history. A seafloor including pelagic clay and carbonate-covered seamounts occurs south and southeast of the southern extent of the Tohoku earthquake rupture zone. This area has no historic tsunami or tsunamigenic earthquakes along the Japan and Izu-Bonin Trenches with the possible exception of the poorly located Enpo earthquake of A.D. 1677. We believe that the seamounts incoming on the oceanic plate to the south and southeast of the Tohoku rupture zone interfere with long-distance propagation of slip in the pelagic clay, limiting earthquake magnitude, shallow slip, and tsunami generation.
Year of Publication: 2015
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; 07 Marine Geology and Oceanography; Arctic Ocean; Carbonates; Clastic sediments; Clay minerals; DSDP Site 346; Deep Sea Drilling Project; Earthquakes; East Pacific; Expedition 345; Expeditions 343/343T; Geophysical methods; Geophysical surveys; Hess Deep; IODP Site C0019; Igneous rocks; Integrated Ocean Drilling Program; Izu-Bonin Arc; Jan Mayen Ridge; Japan Trench; Japan Trench Fast Drilling Project; Kula Plate; Kula-Pacific Ridge; Leg 185; Leg 38; Marine geology; Marine sedimentation; Marine sediments; Microfossils; Mineral composition; North Pacific; Northeast Pacific; Northwest Pacific; Norwegian Sea; ODP Site 1149; Ocean Drilling Program; Ocean floors; Pacific Ocean; Pacific Plate; Plate tectonics; Propagation; Provenance; Pyroclastics; Reflection methods; Rupture; Sedimentation; Sediments; Seismic methods; Sheet silicates; Silicates; Siliceous composition; Smectite; Subduction zones; Surveys; Tohoku-Oki earthquake 2011; Tsunamis; Volcanic ash; Volcanic rocks; West Pacific
Coordinates: N375619 N375620 E1435449 E1435447
Record ID: 2015052316
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