Michas, G; (2016) Generalized statistical mechanics description of fault and earthquake populations in Corinth rift (Greece). Doctoral thesis , UCL (University College London).

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Abstract

The aim of the present thesis is to provide new insights into fault growth processes and the evolution of earthquake activity in one of the most seismically active area in Europe, the Corinth Rift (central Greece). The collective properties of fault and earthquake populations are studied in terms of statistical mechanics and the generalized framework termed as Non-Extensive Statistical Mechanics (NESM). By compiling a comprehensive dataset for the fault network in the Rift, the scaling properties of fault trace-lengths are studied by applying the NESM framework. In the debate of power-law versus exponential scaling in natural fault systems, the analysis indicates the transition from the one end-member to the other as a function of increasing strain in the Rift, providing quantitative evidence for a combination of crustal processes in a single tectonic setting. The results further imply that regional strain, fault interactions and the boundary condition of the brittle layer may control fault growth and fault network evolution in the Rift. The fragment-asperity model, which is derived in the NESM framework, is further used to describe the frequency-magnitude distribution of seismicity and estimate the recurrence times of large earthquakes in the region, supplemented and compared with the empirical Gutenberg-Richter scaling relation. The NESM based analysis of the temporal properties of earthquakes in the Rift indicates that seismicity evolves in temporal clusters, characterized by multifractal structures and both short-term and long-term clustering effects, which indicate highly non-random behavior. Such properties further imply non-linear diffusion phenomena in the evolution of the earthquake activity, a hypothesis that is tested for two case studies of induced seismicity in the Rift. The spatiotemporal properties of the two earthquake sequences are studied in terms of the Continuous Time Random Walk (CTRW) theory and the NESM framework and indicate a non-linear sub-diffusion process in the spatial relaxation of the earthquake activity in the region. Overall, the present thesis, based on the principles of generalized statistical mechanics, provides a physical rationale for the scaling properties of fault and earthquake populations in the Corinth Rift and demonstrates how these properties can provide new insights into the evolution of the earthquake activity and the fault network in the region.

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