About the Project
Project Rationale:
Our understanding of the transition from the lithospheric plate to the weaker asthenosphere has recently been revolutionized by seismic imaging that finds a sharp, strong discontinuity at the base of the plate. These observations require a plate defined by partial melt. However, the dynamic implications of this have yet to be realized. For instance, climate change estimates over geologic timescales depend on estimates of the sea level, which depend not only on the size of the oceans, but the way that the plate sits on the underlying asthenosphere. Understanding the impact plate dynamics on paleoclimate has broad implications for our understanding of the evolution of Earth’s climate and its habitability in the geologic record with implications for the future. This is an exciting opportunity to fully explore the potential impact and interplay between plate tectonics and climate.
Methodology:
The student will play a vital role in a large international project to image and understand the properties that define a tectonic plate, using both newly acquired regional datasets and the global seismic database. The student will use a range of seismic imaging tools and compare to seafloor bathymetry and gravity and apparent subsidence and flexure. These could include characterizing seismicity, surface wave imaging, receiver function imaging, anisotropic investigations, seismic attenuation studies, full waveform modelling, joint seismic inversions, and joint seismic – MT imaging. The student will use the tight constraints on seismic velocity and discontinuity structure in numerical models to constrain the effect of a melt-defined lithosphere-asthenosphere boundary on past rates of seafloor subsidence base on existing multibeam swath and ship borne and gravity free air gravity estimates. Results of these analyses will then be linked to geologic observations from existing seafloor drilling cores to determine their effect on sea level- and elevation-driven climate change estimates over geologic time. A variety of approaches to the imaging and modelling are possible, including, machine learning to identify hidden correlations between geological and geophysical observables.
Interaction with international collaborators is key, since broad impact will be attained by integrating results and incorporating a wide range of seismic resolutions. The student will have the opportunity to travel and develop collaborations with colleagues in USA, France, and Germany.
Training:
All doctoral candidates will enrol in the Graduate School of NOCS (GSNOCS), where they will receive specialist training in oral and written presentation skills, have the opportunity to participate in teaching activities, and have access to a full range of research and generic training opportunities including geophysical field work. GSNOCS attracts students from all over the world and from all science and engineering backgrounds. There are currently around 200 full- and part-time PhD students enrolled (~60% UK and 40% EU & overseas). Specific training will include:
The student will develop skills and learn techniques from seismology and geophysics, with one of the most active geophysics groups in the UK. The student will learn to cull, process, and invert ocean bottom seismic data. The student will utilize excellent computational facilities and be trained in programming for Python, FORTRAN, Matlab, SAC, and UNIX operating system. The project will involve collaborative travel to France, Germany, and the United States. A wide range of opportunities to develop the range of general skills essential for successful completion of the PhD and their future career are available through the Graduate School NOCS. This training will prepare the student for career paths in either academia or industry.
References
Rychert, C. A. and P. M. Shearer (2009) A Global View of the Lithosphere-
Asthenosphere Boundary, Science, 324, doi:10.1126/science.1169754.
Rychert, C. A., N. Harmon, and S. Tharimena (2018), Scattered Wave Imaging of the Oceanic Plate in Cascadia, Science Advances, 4(2), DOI: 10.1126/sciadv.aao1908.
Tharimena, S., C. Rychert, and N. Harmon (2017), A unified continental thickness from seismology and diamonds suggests a melt-defined plate, Science, 357(6351), 580-583.