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

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 in
the 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.

The results from this project can be viewed within the wider societal relevance of understanding tsunamigenic earthquakes. This depends upon a full understanding of the material properties of
subduction inputs, with any future modelling of these inputs requiring an understanding of the 3D distribution of sediment types, their sediment routing and any temporal changes in sediment
provenance, something that can only be achieved by investigating the range of sediment sources (provenance) and their likely contribution to the stratigraphic record. The wider general public, including college students and school children, interested in plate tectonics and natural hazards. (Benefits on a 1-5 year timescale)