Deep crustal structure of the North Anatolian Fault Zone and the earthquake cycle
Principal investigators: Dr S Rost, Dr T Wright, Prof G Houseman, Dr D Cornwall, Dr G Lloyd, Dr R Phillips, Dr T Yamasaki
Sponsor: NERC
Value: £1,161,175.00
Dates: 01/10/2011 - 30/09/2015
Summary
Deformation of the Earth's upper crust is localised onto narrow fault zones, which may slip suddenly and catastrophically in earthquakes. Strain in the upper mantle is more broadly distributed and is typically thought to occur by continuous ductile creep. The transition in the lower crust from broad shear zone to a narrow structure in the upper crust is poorly understood but the properties of the lower crust are an important control on the behaviour of the system during the earthquake loading cycle. The properties of lower crustal rocks, and their spatial variation, cannot be measured directly; instead inferences are typically made from seismic observations, exhumed geological analogues, and simple modelling of surface deformation data. Existing seismic experiments have poor resolution in the lower crust; and current geodetic models do not reproduce observations of rapid post-seismic and focussed inter-seismic strain.
We propose a multi-disciplinary project with the aim of determining the lower crustal structure of the North Anatolian Fault Zone (NAFZ) in Turkey and explaining the geodetic data. We plan
- A novel seismic experiment that will provide high-resolution images of lower-crustal structure beneath the NAFZ,
- Analysis of geodetic measurements of surface displacement, and
- Petrofabric analysis of an exhumed shear zone that has exposed rocks representative of the mid to lower crust under the fault.
We will use these data to constrain geodynamic models of the earthquake cycle using 3D visco-elastic continuum mechanics simulations. Computational experiments simulatingthe visco-elastic deformation of a faulted block driven by boundary forces will be constrained by geodetic and finite strain observations (seismic images and petrofabric analysis) in order to determine the variation of creep viscosity within and around the fault zone. We aim in this project to explain how the earthquake loading cycle for this major fault system is affected by the lower crustal structure, and ultimately to contribute to better assessment of the seismic hazard associated with it. The resulting synthesis of data and model will guide future investigations for other major strike-slip fault zones.