School of Earth and Environment

Institute of Geophysics and Tectonics (IGT) PhD Projects

Mapping and modelling spatial variation in strain accumulation along the North Anatolian Fault

Fully-funded NERC studentship available ASAP.

For eligibility visit www.nerc.ac.uk/funding/available/postgrad/eligibility.asp.

Supervisors: Tim Wright & Greg Houseman

The North Anatolian Fault (NAF) runs for 1300 km across Northern Turkey, and has been responsible for a series of major earthquakes in the 20th Century (Stein et al, 1997). These earthquakes began in eastern Turkey in 1939, and activity has moved progressively westwards, culminating in two M7+ earthquakes in 1999 (Wright et al., 2001a; Burgmann et al, 2002). The aim of this studentship is to measure the strain accumulating across the NAF along its entire length using satellite radar interferometry (InSAR; Wright, 2002). The student will use these data to test numerical models of earthquake cycle deformation and to assess the rheology of the lower crust under the NAF.

Figure 1: InSAR measurements of strain accumulation across the North Anatolian Fault, reproduced from Walters et al (2011).

Figure 1: InSAR measurements of strain accumulation across the North Anatolian Fault, reproduced from Walters et al (2011).

Simple models of earthquake cycle deformation have typically been developed in isolation, to study inter-seismic, co-seismic or post-seismic deformation observed at particular faults. The few models that exist that attempt to model the whole earthquake cycle usually suffer from poor observational constraints. In the rare cases where geodetic measurements of strain are available at different times in the earthquake cycle, simple models with uniform viscosities in the lower crust (e.g. Savage, 2000) are unable to match the observations at different time periods with the same viscoelastic constitutive law. As a result, more complex rheological models have been proposed (e.g. Hetland and Hager, 2005), but not rigorously tested.

Almost the entire length of the NAF ruptured in earthquakes in the 20th Century. If simple models of earthquake cycle deformation are correct, then the present-day strain rates should vary depending on the date of the last earthquake, which ranges from 10 to 70 years depending on location. Sparse GPS data are insufficient to test this hypothesis, expect in the densely instrumented region around the Sea of Marmara. The student will measure strain in a series of locations along the NAF using InSAR by combining multiple interferograms from the Envisat satellite using a network algorithm developed by Wright and collaborators. By combining all available data from the Envisat satellite, and using the latest codes, strain rates can be measured with higher accuracies than was possible when these techniques were being pioneered (Wright et al., 2001b). Furthermore, the network algorithm is optimised for areas of low coherence due to vegetation cover, so should enable reliable estimates to be obtained at multiple locations along the fault.

Specifically, the student will carry out the following tasks:

  1. Using all the available Envisat data, measure strain accumulation profiles at a series of locations along the fault corresponding to locations that ruptured in 1939, 1942, 1943, 1944, 1951, 1957, and 1967. These will be compared with estimates produced independently for the location of the 1999 earthquakes.
  2. Combine all the individual InSAR profiles with available GPS data into a complete velocity field for the whole North Anatolian Fault, using methods recently developed at Leeds (Wang and Wright, 2010).
  3. Test analytical and numerical models of earthquake cycle deformation to determine whether a single crustal creep law, with uniform properties, can explain all the observed deformation along the NAF.

The studentship is part of a large funded NERC proposal based at Leeds to investigate the “Deep crustal structure of the North Anatolian Fault Zone and the earthquake cycle”. The student will be expected to interact with the interdisciplinary team of geologists, geodesists and seismologists working on this project. They will also have the opportunity to be involved with the seismic field experiment in Turkey.

The project would suit a reasonably numerate physical scientist with a first degree in Earth Sciences, Physics or a related discipline. The student will be a member of a vibrant team of PhD researchers at the University of Leeds. They will also be part of the National Centre for Earth Observation, and be expected to attend and present their results at NCEO meetings as well as other national and international conferences and workshops.

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