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Non Extensive Thermodynamics and Statistical Mechanics in Earthquake Physics & rock fracture

Final Report Summary - NEXT EARTH (Non extensive thermodynamics and statistical mechanics in earthquake physics & rock fracture)

In a wide range of problems in Earth Physics, from earthquake prediction to the driving forces of plate tectonics, it is necessary to understand how rocks deform. The rock physics approach to understanding these geophysical processes is based on the premise that the macroscale behavior of rocks is governed by microscale interactions. As in fracture, the physics of an ensemble of earthquakes (fractures) is a subject with many unknowns and has to be studied with a different approach than the physics of a single one. In this sense in NEXT EARTH we used the statistical physics principles not only as appropriate but as a necessary frame to understand the collective properties of earthquakes and fractures.

To answer the fundamental question on the type of statistical physics which is appropriate to commonly describe effects from fracture level to seismicity scale, within NEXT EARTH, we proposed the application of non-extensive thermodynamics, introduced by Tsallis, as the integrated pathway for the analysis of laboratory results along with earthquake events catalogues, contributing to improved methodologies for investigating the evolution of earthquakes and fracture events. Through the application of the first principles of non-extensive statistical physics we have provided insights into the fundamental behaviour of the Earth system.

The main results from the NEXT EARTH project have been to employ a universal methodology to describe the physics and mechanics of fracture from a laboratory scale, through to crustal fracturing, to a plate tectonics scale. The NEXT EARTH project has met its principal objective in demonstrating that non extensive statistical physics (NESP) can predict the observed common scaling in rock fracture and earthquake physics, interpreting this within a universal fundamental framework, leading to the hypothesis that non-extensive statistical physics is the methodological pathway through which fracture and earthquake physics should be interpreted. Furthermore acoustic emissions and electrical relaxation results in experiments on rocks under stress conditions were used to validate the applicability of NESP to physical phenonmena that could be used as earthquake forerunners at a geodynamic scale.

Within the concept of NEXT EARTH the following scientific questions were addressed:
- Is plate tectonics a case of non-extensive thermodynamics?
- A non-extensive statistical physics approach to the polarity reversals of the geomagnetic field.
- Non-extensive statistical physics approach to fault population distribution. A case study from the Southern Hellenic Arc (Central Crete).
- A non-extensive statistics of the fault-population at Valles Marineris province, Mars.
- Evidence of non-extensive thermodynamic lithospheric instability at the approach of the 2004 Sumatran- Andaman and 2011 Honshu mega-earthquakes.
- A spatiotemporal non-extensive investigation of seismicity surrounding the L'Aquila earthquake, ML5.8 on 6th April 2009.
- Non-extensivity of isothermal depolarization relaxation currents in compressed rock.
- Experimental evidence of a non-extensive statistical physics behaviour of fracture in triaxially deformed Etna basalt using acoustic emissions.
- Moving charged dislocations and pressure stimulated currents. From fracture processes to earthquake physics in a non-extensive thermodynamic view.
- Evidence of non-extensivity and application of natural time analysis in the Seismic activity in Eyjafjallajökull volcano.
- Non-extensivity in pressure sensitive currents (PSC) from rock sample.

The fellowship has been entirely successful in facilitating a senior European researcher to move to a top European university and initiate a new research strategy in Earth Physics.