Themes: Geological Sciences, Earth, Universe
location: Seismic Risk Assessment Section (BERSSIN) - Fontenay-aux-Roses (92)
Master degree in Earth Sciences or equivalent - Basic skills and strong interest in quantitative methods applied to geology: geodesy, geophysics, seismology, computer programming.
Age limit: 26 years old unless otherwise stated.
The objective of this thesis is to develop new methods for the integration of geodetic strain velocity data into the characterization of seismogenic sources. Geodetic data (GPS measurements) have been used for about two decades in comparison with the slip rates of faults and with seismicity. In tectonically “simple” regions with high seismic activity (eg, San Andreas fault), we observe a first order agreement between the geodetic strain rates, the fault rates measured by geological methods, and the rate of strong earthquakes known from catalogs. In recent years, developments in methods for analyzing geodetic data and the sharp increase in the density of GPS networks have made it possible to significantly improve the resolution of deformation rates. These developments thus make it possible to use this new data to test their role in the characterization of the seismogenic sources used in the probabilistic calculation of seismic hazard. In order to address these questions, this thesis project will aim to integrate geodetic deformation data and those from geology into fault system models allowing the generation of synthetic seismicity catalogs, which will be tested against instrumental, historical and paleoseismological seismicity catalogs. These studies will be based on the most recent methodological developments *. The target site for this thesis is the Central Apennines region in Italy. In particular, two major points must be tested: (1) What is the part of seismic and aseismic deformation (eg, post-seismic creep) in the estimates of deformation rates at the scale of a fault up to the regional scale? (2) Can we constrain and characterize seismic super-cycles (periods of intense activity on fault systems followed by periods of quiescence) as suggested by several researchers recently? The first challenge of the thesis will consist in developing a set of methodologies to extract differential velocities useful for the parameterization of seismogenic sources. This work will be based on recent doctoral and master’s work in host laboratories, in particular in order to estimate fault rates with uncertainties (probability distribution) as precise as possible. The second challenge of the thesis will be to configure a model of seismogenic sources integrating both geological and geodetic data. The major questions addressed in this work will relate to the attribution of seismic and aseismic deformation at both the scale of the fault systems and at the scale of individual faults, the confrontation between the parameterization of models with geological data of long-term deformation (Quaternary), and more generally the characterization of possible seismic scenarios.
* Masson, C. et al . Solid Earth, 2019; Chartier et al. ,SRL ,2019