International Ocean Discovery Program; Expedition 362 scientific prospectus; the Sumatra subduction zone; the role of input materials in shallow seismogenic slip and forearc plateau development

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doi: 10.14379/iodp.sp.362.2016
Author(s): McNeill, Lisa C.; Dugan, Brandon E.; Petronotis, Katerina E.
Author Affiliation(s): Primary:
University of Southampton, National Oceanography Centre-Southampton, Southampton, United Kingdom
Rice University, United States
Texas A&M University, United States
Source: Scientific Prospectus (International Ocean Discovery Program), Vol.362, 21p. Publisher: International Ocean Discovery Program, College Station, TX, United States. ISSN: 2332-1385
Note: In English. 80 refs.
Summary: The 2004 Mw 9.2 earthquake and tsunami that struck North Sumatra and the Andaman-Nicobar Islands devastated coastal communities around the Indian Ocean and was the first earthquake to be analyzed by modern techniques. This earthquake and the Tohoku-Oki Mw 9.0 earthquake and tsunami in 2011 showed unexpectedly shallow megathrust slip. In the case of North Sumatra, this shallow slip was focused beneath a distinctive plateau of the accretionary prism. This intriguing seismogenic behavior and forearc structure are not well explained by existing models or by relationships observed at margins where seismogenic slip typically occurs farther landward. The input materials of the North Sumatran subduction zone are a distinctive, thick (up to 4-5 km) sequence of primarily Bengal-Nicobar Fan-related sediments. This sequence shows strong evidence for induration and dewatering and has probably reached the temperatures required for sediment-strengthening diagenetic reactions prior to accretion. The correspondence between the 2004 rupture location and the overlying prism plateau, as well as evidence for a strengthened input section, suggests the input materials are key to driving the distinctive slip behavior and longterm forearc structure. The aim of Expedition 362 is to begin to understand the nature of seismogenesis in North Sumatra through sampling these input materials and assessing their evolution, en route to understanding such processes on related convergent margins. Properties of the incoming section affect the strength of the wedge interior and base, likely promoting the observed plateau development. In turn, properties of deeper input sediment control decollement position and properties, and hence hold the key to shallow coseismic slip. During Expedition 362, two primary, riserless sites (proposed Sites SUMA-11C and SUMA-12A) will be drilled on the oceanic plate to analyze the properties of the input materials. Coring, downhole pressure and temperature measurements, and wireline logging at these sites will constrain sediment deposition rates, diagenesis, thermal and physical properties, and fluid composition. Postexpedition experimental analyses and numerical models will be employed to investigate the mechanical and frictional behavior of the input section sediments/sedimentary rocks as they thicken, accrete, and become involved in plate boundary slip system and prism development. These samples and downhole measurements will augment the internationally collected site survey bathymetric, seismic, and shallow core data that provide the regional geological framework of the margin.
Year of Publication: 2016
Research Program: IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; 18 Geophysics, Solid-Earth; Accretionary wedges; Asia; Basins; Boreholes; Drilling; Earthquakes; Expedition 362; Far East; Faults; Fore-arc basins; Indian Ocean; Indonesia; International Ocean Discovery Program; Marine drilling; Marine sediments; Planning; Plate tectonics; Sediments; Subduction zones; Submarine fans; Sumatra
Coordinates: N024500 N030600 E0915200 E0913700
Record ID: 2016043043
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