***This studentship is fully funded for UK students through COMET and the BGS***

Project Title: The dynamics of dip-slip faulting across multiple timescales

 Supervisory Team:

• Dr Tim Craig (University of Leeds – Primary Supervisor)
• Dr Ekbal Hussain (British Geological Survey)
• Prof. Tim Wright (University of Leeds)
• Dr Alex Copley (University of Cambridge)
• Dr Laura Gregory (University of Leeds)

Host Institution: University of Leeds, UK.

Deadline: Applications will close on Thursday 22nd April 2021

Project Summary:

This project aims to understand the factors that control the behaviour of dip-slip faults across a range of timescales, from individual stages of earthquake cycles, to their geological evolution over millions of years. This project will draw on a wealth of new geological and geophysical observations and data, and produce new numerical geodynamic models aimed at understanding the evolution and behaviour of dip-slip faults.

 The initial aim for this project will be to analyse geodetic (GPS, InSAR) data to determine the surface motions before, during, and after dip-slip earthquakes. We will then develop models that will allow us to use the observations to infer the rheology and dynamics of the brittle and ductile parts of the crust, using realistic structural and rheological parameters for the fault zone. Of particular interest is how the brittle (and potentially seismogenic) portion of the fault interacts with ductile shear zones at depth, how this interaction controls the geometry and rate of deformation at the timescale of individual earthquake cycles, and how this behaviour ultimately governs the longer-term geological evolution of the fault system and the bounding basins and mountain ranges. An underlying aim of the project will be to use this work to establish how to estimate the pattern of interseismic strain accumulation on active dip-slip fault systems, as a means to improving our understanding of the hazard posed by these faults.

As the project is aimed at understanding globally-applicable concepts, it is geographically unconstrained, but initial target fault systems of interest may include the active fault systems of western United States, eastern Africa, Greece, Italy, Papua New Guinea, and western Anatolia. The initial project is not planned to involve fieldwork, we expect there to be opportunities to participate in fieldwork on related projects in later years.

This initial work coupling geodetic observations to dynamic models of earthquake cycles will not only answer a number of fundamental scientific questions, but will also provide the opportunity for the student to develop relevant observational techniques and skills in numerical geodynamic modelling. Following this initial work, a number of avenues exist to focus on in the later years of the project, depending on the interests and skillset of the student and the nature of the initial results. These include, but are not limited to:

• Modelling the evolution of large-offset normal faults, and the impact that increasing footwall erosion and hangingwall sedimentation have on the dynamics of the system, and how this development of the fault system feeds into the longer-term landscape and geological structure.
• Constraining the along-strike segmentation of normal fault arrays, and how this may be controlled by shear-zone geometries at depth.
• Comparative studies investigating how varying crustal architecture and composition influence the rheological structure of the fault system, and how this impacts on the deformation patterns seen.
• Investigating the across-strike migration and transfer of strain amongst dip-slip fault arrays, where multiple faults are active at once.
• Modelling the rheological evolution of large-offset detachment faults, and how this impacts their earthquake behaviour.
• Should a major dip-slip earthquake of particular interest occur during the duration of the studentship, the student may have the opportunity to work on the scientific response to this event as part of the COMET team.
• Performing determinisitic or probabilistic hazard assessments for dip-slip faults, based upon our new results regarding the dynamic controls on their behaviour.

References:

• Craig and Parnell-Turner (2017). Depth-varying seismogenesis on an oceanic detachment fault at 13^o20’N on the Mid-Atlantic Ridge, EPSL, v479, pp60-70.
• Copley et al., (2018). Unexpected earthquake hazard revealed by Holocene rupture on the Kenchreai Fault (central Greece): implications for weak sub-fault shear zones. EPSL, v486, pp141-154.
• Biemiller et al., (2020). Mechanical implications of creep and partial coupling on the worlds fastest slipping low-angle normal fault in southeastern Papua New Guinea, JGR, v125, doi:10.1029/2020JB020117.
• Hussain et al, (2020). Contrasting seismic risk for Santiago, Chile, from near-field and distant earthquake sources, Natural Hazards and Earth System Sciences, v20, pp1533-1555.
• Walters et al., (2018). Dual control of fault intersections on stop-start rupture in the 2016 Central Italy seismic sequence. EPSL, v500, doi: 10.1016/j.epsl.2018.07.043.
• Weiss et al., (2020). High-resolution surface velocities and strain for Anatolia from Sentinel-1 InSAR and GNSS data. GRL, v47, pp:e2020GL087376.

Training: The student will work primarily in Leeds under the supervision of Dr Tim Craig, Prof. Tim Wright, and Dr Laura Gregory within the Institute for Geophysics and Tectonics. Regular collaboration with Dr Alex Copley and Dr Ekbal Hussain will be facilitated remotely and by regular visits to the partner institutions, with an expectation that the student would spend longer periods of time at the BGS in Keyworth and in Cambridge as the project requires. The student will receive training in satellite geodesy, observational earthquake seismology and numerical geodynamic modelling. The student will benefit from networking and training available through the NERC-funded Centre for the Observation and Modelling of Earthquakes and Tectonics (www.comet.nerc.ac.uk), with whom the student will be able to interact. Within Leeds, they will have the opportunity to interact with internationally-excellent research groups in Tectonics and Structural Geology, hosted within the Institute for Geophysics and Tectonics.

Applicant Background: This project would suit candidates with a background in quantitative geology, geophysics, or physics with an interest in solid-Earth processes. Prior skills in computer programming, observational geodesy, seismology or numerical geodynamic modelling are desirable, but not required.

To apply: For further information, and to discuss the project and applications, please contact t.j.craig@leeds.ac.uk, and include your current CV.