Provenance of Nicobar Fan sediments from IODP Expedition 362, offshore Sumatra

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Subduction zones, where one plate is forced beneath another, are the locations of the largest-magnitude earthquakes, often associated with the generation of tsunamis that pose a natural hazard. Such tsunamigenic earthquakes are caused by slip events along the upper part of the subducting plate in the so-called "seismogenic zone". The material properties of the incoming plate and its sediment cover ("subduction inputs"), likely linked to changing sediment types over time from different sediment sources or provenances (the focus of this research proposal), play a critical role inthe generation of tsunamigenic earthquakes. The sediment types and the way in which they are stacked in three dimensions (called "lithostratigraphy") exerts a first-order influence over the material properties and tectonic behaviour of subduction zones2. The 3D location and proportion of coarse- versus fine-grained deep-marine sediments are appreciated among geotechnical engineers and geologists to affect coefficients of friction and permeability of the subduction inputs. This proposed research will contribute significantly to an improved understanding of these problems by focussing on the thick sedimentary pile entering a subduction zone3, and provide a comparative study to that of IODP Expedition 322, offshore Japan (on which the PI was a shipboard scientist), that investigated input materials transported by subduction toward and beneath the frontal so-called Nankai accretionary prism.