Geology & Geophysics Group
Convergent margins & subduction processes
Subduction zones are areas of the Earth where two tectonic plates collide. The return of plate material into the mantle results in potential for major geohazards: large earthquakes such as those in 2004 and 2005 offshore Sumatra can cause tsunami; volcanoes such as Krakatoa have also been linked with short-term changes in global climate. The fluxes of material are associated with transfer of chemicals between the oceans, crust, mantle and atmosphere. Accumulation and deformation of sediments can make convergent margins important locations for gas hydrate reservoirs and chemosynthetic communities.
Key areas of research include:
- What are the main active fault structures within a subduction zone forearc, and how do forearcs evolve through time? How do these structures relate to earthquake potential and location?
- How structures that we can map at the seafloor (the geomorphology) relate to the plate boundary at depth - this may be important as a control on the tsunami hazard, but the seafloor structures might also act as an indication of the physical state of the main fault between the two plates.
- Controls on the size of earthquakes at subduction zones - the main plate boundary faults rupture as individual segments, but are there relationships between physical properties and earthquake rupture that we can measure and determine how and where active faults break?
- What are the similarities and differences between subduction zones around the world?
- What is the distribution of gas hydrates at subduction zones? Are the total volumes significant?
Above: Swath bathymetry collected by HMS Scott offshore of Sumatra over the December 26, 2004, fault rupture zone.
Recent projects related to subduction zones include:
- Geomorphology and structure of the Sumatran forearc, links between structure and earthquake rupture
- Forearc structure, evolution and interpretation of past earthquake records from the Cascadia subduction zone
- Deep ocean drilling of subduction zone forearc sediments to determine physical properties, deformation, fluid flow, seismogenic zone properties and forearc evolution, e.g. Nankai and Sumatra
- Large-scale structure and evolution of the Mendocino Triple Junction
- Seismic imaging, properties and modelling of gas hydrates.
- Composition and crustal structure of the Aleutian island arc.
G&G personnel working on this area of research:
