The Department of Earth Sciences is seeking to fill two PhD positions of in total 11 within the EU TREAD doctoral network: 'Data and Processes in Seismic Hazard'. The two positions at Utrecht University offer a four-year PhD track with help of additional non-EU funding, in contrast to the other 3-year tracks in the network. A personalised training programme will be set up, reflecting your training needs and career objectives. About 20% of your time will be dedicated to this training component, which includes training on the job in assisting in the BSc and MSc teaching programs of our department.

The two Utrecht-based projects are:

• Project #5: Flow to friction transition and back in carbonate rocks.

Main supervisor: Dr André Niemeijer (Experimental Rock Deformation group / High Presssure & Temperature Lab)

Objectives: The rheology of carbonates during the seismic cycle, especially in the presence of pressurized fluids and at the viscous-plastic to elasto-frictional transition, remains poorly understood.

In the project, we will perform experiments on both intact carbonate rocks as well as fault gouges under conditions where the transition from crystal-plastic flow to frictional behaviour might be activated. Detailed microstructural analyses down to the nanoscale (UU & UNIPD) of the experimental products and comparison with natural fault rocks from the deep roots of fault zones exposed in the Apuan Alps (Italy) and Western Alps (Switzerland) (UNIPD) will allow us to:

1. test whether the deformation mechanisms activated in the experiments occur in natural faults,
2. test and update existing calcite paleo-piezometers to estimate the state of stress at earthquake nucleation depths and beyond,
3. define the conditions under which the transition from volume-conservative crystal-plastic deformation to volume-dependent frictional deformation occurs (i.e., viscous-plastic to elasto-frictional transition).

Additionally, existing flow laws for creep in fine-grained calcite aggregates that have been used to predict shear strength during seismic sliding will be tested and updated, also for their utilization in other fellow projects on the modelling of the seismic cycle proposed in TREAD.

Expected Results:

1. Identification of the dominant deformation mechanisms across the transition from friction to flow behavior in experimental and natural carbonate fault rocks?
2. Updated and tested microphysical models (laws) for the full range of velocities encountered in the seismic cycle? (3) Critical assessment of existing paleopiezometers for wet calcite rocks.

• Project #7: How tectonics affects seismic hazard parameters in complex continental settings.

Main supervisor: Dr Ylona van Dinther (Tectonics group)

Objectives: Recent 2D tectonic earthquake sequence modelling of the Northern Apennines reveals that realistic tectonic loading and deep structures and rheology have a major impact on earthquake sequences in the upper continental crust. Specifically, the stress field and the type, distribution and rate of earthquakes in Northern Apennines are significantly affected by slab pull and lower crustal rheology, although these are not taken into account in earthquake sequence modelling or seismic hazard assessment. To understand these key features this doctoral candidate will:

1. extend 2D/3D visco-elasto-plastic, seismo-thermo-mechanical models, simulating earthquake sequences following millions of years tectonic, topography and fault evolution, down to milliseconds of earthquakes from strike slip to complex continental settings. To computationally efficiently simulate wave-mediated stress transfer in 3D, faults stress states will be coupled to the dynamic rupture model following recent achievements.
2. apply these new state-of-the-art models to spontaneously simulate and understand seismic hazard parameters (i.e., Mmax and b-value) as a function of important tectonic and rheological parameters (e.g., loading by mantle and lower crust, carbonate rheology, fluid flow).
3. tightly constrain a scenario in the Betics by observations from field studies, geodesy, seismology and fault geometries, and microphysical friction laws, using instantaneous modelling to assess its seismic hazard and compare those outcomes to more traditional PSHA approaches to converge towards a more physics-inspired PSHA methods.

Expected Results:

1. 2D/3D coupled visco-elasto-plastic tectonic earthquake sequence models for complex continental settings?
2. Improved understanding of how key tectonic and rheological parameters affect seismic hazard parameters in complex continental settings?
3. Data-constrained physics-based scenario for seismic hazard assessment in the Betics.

Qualifications:

You must hold a Master's degree in Geophysics, Physics, Earth Sciences, Geology or an equivalent relevant degree. PhD recipients cannot be considered. You have a keen interest in pursuing geological/geophysical problems. You have excellent written and spoken English skills and be highly motivated to work in an international team.

• For Project #5, additional advantageous skills are: affinity with HPT lab work, microstructures and deformation mechanisms.
• For Project #7, additional advantageous skills are: programming, numerical modelling.

Terms of employment:

You will be offered a temporary position initially for one year with an extension to a total of four years upon a successful assessment in the first year, and with the specific intent that it results in a doctorate within this period. The gross salary ranges between €2,541 in the first year and €3,247 in the fourth year of employment (scale P according to the Collective Labour Agreement Dutch Universities) per month for a full-time employment. Filling the position 0.8 FTE is optional.

Salaries are supplemented with a holiday bonus of 8% and an end-of-year bonus of 8,3% per year. Utrecht University offers excellent secondary conditions, including an attractive retirement scheme, (partly paid) parental leave and flexible employment conditions (multiple choice model). For more information, please visit working at Utrecht University. Facilities for childcare and sports are available on campus.

About the organisation:

Utrecht University's Faculty of Geosciences studies the Earth from the Earth's core to its surface, including man's spatial and material utilisation of the Earth, always with a focus on sustainability and innovation. With a population of 3,400 students (BSc and MSc) and 720 staff, the Faculty is a strong and challenging organisation. The Faculty is organised in four Departments: Earth Sciences, Physical Geography, Sustainable Development, and Human Geography & Spatial Planning.

The Department of Earth Sciences conducts teaching and research across the full range of the solid Earth and environmental Earth sciences, with activities in almost all areas of geology, geochemistry, geophysics, biogeology and hydrogeology. The department hosts a highly international tenured staff of about 50 scientists and more than 110 PhD students and postdoctoral researchers. Our research programme spans four intertwined themes: Climate & Life, Earth interior, Earth materials, and Environmental Earth Sciences. We house or have access to a wide variety of world-class laboratories.

About Utrecht:

Utrecht is the fourth largest city in the Netherlands with a population of nearly 360,000 and forms a hub in the middle of the country. Its historic city centre and its modern central station can easily be reached from the Utrecht Science Park by public transport or by a 15-minute bicycle ride. Utrecht boasts beautiful canals with extraordinary wharf cellars housing cafés and terraces by the water, as well as a broad variety of shops and boutiques.

Additional information:

For informal questions, please contact Dr André Niemeijer (project leader) via a.r.niemeijer@uu.nl.

How to apply:

To apply, please go to the general vacancy page of the EU-TREAD doctoral network and follow the application guidelines there. The application deadline is April 15^th, 2023.

Please note that international candidates that need a visa/work permit for the Netherlands require at least four months processing time after selection and acceptance. This will be arranged with help of the International Service Desk (ISD) of our university. Finding appropriate housing in or near Utrecht is your own responsibility, but the ISD may be able to advise you therewith.

Online screening may be part of the selection. Commercial response to this ad is not appreciated.