Earthquakes and fault interaction in western Turkey

Primary supervisor: Dr Zoë Mildon (University of Plymouth)

Secondary supervisor: Dr Sarah Boulton (University of Plymouth)

Additional Supervisors:

Dr Ekbal Hussain, (British Geological Survey, BGS). Email: ekhuss@bgs.ac.uk

Dr Cengiz Yildirim, (Istanbul Technical University). Email: cyildirim@itu.edu.tr

Dr Ioannis Papanikolaou, (Agricultural University of Athens). Email: i.pap@aua.gr

Scientific background

Western Turkey and the eastern Aegean Sea is a tectonically active region of north-south orientated extension that forms a series of east-west trending graben structures, with a historical record of large and damaging earthquakes. 

Seismogenic normal faults are exposed at the surface as post-glacial faults scarps, thus the fault geometry and slip rates can be deduced from field measurements. 

Although active faults are well-constrained, potential fault interactions and the strain accumulation of the region is poorly quantified at present leading to potential errors in the understanding of the earthquake hazard. 

This project will address this knowledge gap and provide insights into the earthquake cycle that can be applied to other regions.

Research methodology

The student will use a combination of field mapping and computer-based modelling to understand earthquake interaction and strain accumulation in the region. 

Fieldwork will be conducted in western Turkey to map the geometry and slip rates of under-studied faults, to complement existing literature. Historical data of shaking and damage will be analysed to determine the location and magnitude of historical earthquakes. 

Using the field data and historical earthquake data, fault models with representative variable fault geometry will be built. These will be used to calculate static (Coulomb) stress transfer which is used to analyse whether the triggering of earthquakes and fault interaction. 

This approach will be used to model stress changes associated with historical earthquakes over time to analyse the interaction between faults and the seismic hazard in the region. Strain and therefore stress will accumulate on the faults due to tectonic loading in the time between earthquakes. 

This will be studied using Interferometric Synthetic Aperture Radar (InSAR) and GPS analysis.

Training

The student will gain practical fieldwork skills in an area of active tectonics. Training to use modelling software and in InSAR analysis will be provided by the supervisory team.

Person specification

We are looking for applicants with an undergraduate degree in Geology, Geophysics or Physics and an interest in earthquake hazard and neotectonics, who is willing to undertake fieldwork in Turkey. 

The student should be numerically literate, experience of using Matlab and familiarity with Linux is desirable but not essential.

Understanding the earthquake cycle is of fundamental importance for understanding how, why and where earthquakes might occur and the resulting seismic hazard. 

The earthquake cycle mainly comprises of interseismic (between earthquakes) loading, and coseismic deformation and stress transfer. This project will address both parts of the earthquake cycle, using a combination of field data, static (Coulomb) stress modelling of historical earthquakes and InSAR/GPS modelling of interseismic movement across the region. The study area will be the extensional region of western Turkey and the eastern Aegean Sea. 

This area is chosen based on the good exposure of fault scarps, information on historical earthquakes (magnitudes up to M7.0) and good InSAR coverage.

Coulomb stress transfer (CST) following a normal faulting earthquake typically transfers positive stress along-strike of the fault that moved and negative stress across-strike (Stein, 1999). 

In terms of triggering subsequent earthquakes, the along-strike CST is studied closely, but the role of the negative CST in delaying earthquakes is rarely studied in detail. The arrangement of normal faults in western Turkey, east-west faults forming a series of grabens aligned north-south, provides an ideal opportunity to investigate across-strike interactions more closely. 

CST from historical earthquakes will be summed together to calculate how the stress on faults evolves over time. The interseismic strain and loading of the faults (due to large-scale tectonic motions) will be investigated using InSAR/GPS analysis. This knowledge will be complementary to the stress transfer modelling of historical earthquakes and fault interaction and will be used to assess current models of the regional seismic hazard.

This project aims to address the gap in our knowledge of how across-strike fault interactions may affect earthquake clustering and how tectonic strain is accommodated across such faults. This will enable a better understanding of the seismic hazard in this region, which is typically understudied in comparison to the North Anatolian Fault in Turkey.

There are four key objectives of this project:

  • Compile a database of historical earthquakes in the region from historical data, including calculating earthquake magnitudes where necessary and assigning the earthquakes to known faults.
  • Undertake fieldwork in western Turkey to constrain fault geometry and slip rates on understudied faults.
  • Model Coulomb stress changes associated with historical earthquakes, investigate the importance of across-strike fault interaction and relate these findings to earthquake hazard.
  • Use InSAR and GPS to quantify the strain rate across the region to understand interseismic loading between earthquakes.

There will be the opportunity for the student to develop the Coulomb stress or the InSAR/GPS modelling and to apply the findings to seismic hazard and/or fault interaction and growth, depending on the particular interests of the student. The student will have the opportunity to work with a team of diverse and internationally-renowned supervisors. 

Project-specific training in modelling and fieldwork in regions of active faulting will be provided by the supervisory team, this will provide a complementary skill set for the personal development of the student.

Funding

This project has been shortlisted for funding by the ARIES NERC Doctoral Training Partnership. Undertaking a PhD with ARIES will involve attendance at training events.

ARIES is committed to equality & diversity, and inclusion of students of any and all backgrounds. All ARIES Universities have Athena Swan Bronze status as a minimum.  

Applicants from quantitative disciplines who may have limited environmental science experience may be considered for an additional 3-month stipend to take appropriate advanced-level courses.

Usually, only UK and EU nationals who have been resident in the UK for three years are eligible for a stipend. Shortlisted applicants will be interviewed on 26/27 February 2019.

For further information please see www.aries-dtp.ac.uk or contact us at aries.dtp@uea.ac.uk.