Fully Funded Leverhulme PhD Scholarship: What controls seismic behaviour at subduction zones? Resolving the physical properties of slowly slipping fault zones
Dr R Bell
Prof JV Morgan
Prof M Warner
No more applications being accepted
Funded PhD Project (European/UK Students Only)
Fully-funded Leverhulme Scholarship available to home/EU students from October 2019
Deadline for applications- August 15th 2019
Project PDF can be found here: https://www.imperial.ac.uk/media/imperial-college/faculty-of-engineering/earth-science-and-engineering/phd-opportunities/2019-20-phd-intake/Info-Sheet---Leverhulme-funded---Seismic-behaviour-at-subduction-zones.pdf
Subduction margins produce some of the largest and most destructive earthquakes and tsunami on Earth. Since 2004 >250,000 people have been killed as the direct or indirect result of subduction zone earthquakes. Recent earthquakes (e.g., 2011 Tōhuku-oki, Japan and 2004 Sumatra-Andaman) have demonstrated our poor understanding of the complex behaviour of these fault zones and underestimation of their impact. The discovery of a completely new style of slip mechanism, episodic slow slip events, in which slip occurs faster than the plate motion rate but too slowly to produce seismic waves, is one of the most exciting discoveries in the field of Earth Science of the last two decades. In order to understand how subduction zone earthquakes rupture and to effectively manage and mitigate the hazards they pose, we need to improve our understanding of the processes that govern different styles of subduction zone seismic behaviour.
The Hikurangi subduction zone, along the east coast of the North Island of New Zealand is an ideal place to investigate the physical properties of fault zones which host slow slip, because slow slip events here occur at depths less than 2 km below the seabed, meaning it is possible to image the slowly slipping fault zone with active-source seismic reflection methods (Fig. 1, Bell et al. 2014). Although seismic reflection data can tell us about the geometry of faults, a high-resolution model of the P-wave velocity would provide greater insight into the lithology and fluid properties of the fault zone and overriding plate. A new technique, called full-waveform inversion (FWI), has recently become computationally feasible in 3D, which now allows velocity models to be produced with a very high level of detail (Fig. 2, Morgan et al. 2013).
In 2017-2018 a 3D onshore-offshore seismic dataset was collected across the north Hikurangi margin, optimally for 3D FWI (Fig. 3). We are looking for a numerate geophysicist/computational scientist interested in developing and then interpreting models of P-wave velocity from the new active source 3D data. The goal of this PhD project is to (i) develop a 3D P-wave velocity model across the Hikurangi margin utilising Multi-channel seismic reflection, ocean bottom seismometer and land-seismometer data using conventional tomographic methods, (ii) use this as a starting model for FWI in order to recover high-resolution velocity information for the plate boundary in an area of slow slip and (iii) interpret the velocity model to reveal the structure, lithology and fluid presence within the slow slip zone and overriding plate, drawing on information from recent scientific drilling that has been done across the subduction zone.
Results will be published in high-profile journals and the PhD student will have the opportunity to present findings in at least one international conference. This is an international project and will involve project partners at JAMSTEC, Japan (Prof. Shuichi Kodaira, Dr. Ryuta Arai), the University of Southampton (Prof. Lisa McNeil), Cardiff University (Dr. Ake Fagereng), University of Birmingham (Prof. Tim Reston), University of Texas (Prof. Nathan Bangs) and GNS Science, New Zealand (Dr. Stuart Henrys). The PhD student will be expected to visit the project partners for meetings and discussion.
Please see the NZ3D FWI project website (https://nz3dfwi.weebly.com/home.html) and twitter feed (@NZ3D_FWI) for more information
To apply Please contact Rebecca Bell ([Email Address Removed]), including a CV with your course grades with your email.
- Bell et al. 2014, Hikurangi margin tsunami earthquake generated by slow seismic rupture over a subducted seamount, EPSL, v 397, p1-9
- Morgan et al. 2013, Next generation seismic experiments: Wide-angle, multi-azimuthal, 3D full-waveform inversion, Geophys. J. Int, doi: 10.1093/gji/ggt345