Final Report Summary - GLASS (InteGrated Laboratories to investigate the mechanics of ASeismic vs. Seismic faulting)
The extent to which earthquake phenomena can be accurately assessed depends on how well the underlying physical conditions and processes are understood. But what methodologies are available to investigate processes occurring at a depth of several kilometres in the Earth’s crust? Seismologists characterize fast (seconds) and slow (days
to months) deformation processes but they cannot shed light on the nature of the fault rocks responsible for seismic behaviour. Geologists document long‐term processes (up to millions of years) that can alter fault structure and composition, but in most cases they are unable to relate geological features to specific slip phenomena. Experimentalists test the physical properties of fault rocks, but they have to face the complex problem of bridging the scaling gap between experimental and natural phenomena. Due to the impossibility of developing a comprehensive study of earthquake processes using only a single discipline, GLASS has tried to look at the mechanics of faulting from different angles since there is much learn by considering phenomena at the boundaries between different disciplines. In addition we think that to develop an innovative research a prerequisite is the availability of high-resolution infrastructures that allow the analyses of innovative and original data sets. For this reason we have spent the first half of the project working day by day with mechanical and electronic engineers to develop our research infrastructures: the BRAVA rock deformation apparatus and the three shallow (~250 meter) borehole seismometers within the TABOO research network.
Our interdisciplinary approach linked with the new state-of-the-art infrastructures allowed for a comprehensive understanding of the spectrum of fault slip behaviour from the crustal to the nano-scale and in the time-window spanning from the earthquake co-seismic phase (a few seconds) to the entire fault history (millions of years).
We have started from the characterization of fault zone structure of carbonate/phyllosilicate rich faults showing that fault zone structure (localized vs. distributed) and deformation mechanisms are mainly influenced by the protolith lithology. The one-to-one comparison between fault zone structure mapped at the surface versus the one reconstructed by high-resolution aftershock locations defines an image of active carbonate-bearing faults consisting of parallel and interacting slipping segments extending for a width of about 1.5 km.
We have discovered that frictionally induced grain sensitive superplastic behaviour can account for the onset of dynamic weakening and also thermal decomposition occurs on carbonate faults during earthquake propagation.
For carbonate/phyllosilicate rich faults we have documented the long-term frictional weakness in décollements of tectonic wedges, the fast healing of calcite induced by the interplay of numerous physico-chemical processes, and seismic vs. aseismic creep controlled by mineralogy and fault fabric.
We have characterized systematic variations of the physical properties of experimental faults across the transition from stable sliding, slow- to fast- slip earthquakes.
Apart for earthquake phenomena, results from GLASS have potential impact on the energy field (fault and permeability, the role of fluid pressure in induced seismicity), environment (characterization of host rocks for radioactive waste and natural examples of CO2 geological storage) and landslides (frictional stability of large landslides in the Alps).
GLASS has been a fantastic opportunity for enhancing our research environment: for example several PhD and Post-Doc students have developed their training through research activities on the different scientific topics of the project and researchers from different countries have come to Roma to use BRAVA facilities and for a scientific exchange.
Our interdisciplinary approach linked with the new state-of-the-art infrastructures allowed for a comprehensive understanding of the spectrum of fault slip behaviour from the crustal to the nano-scale and in the time-window spanning from the earthquake co-seismic phase (a few seconds) to the entire fault history (millions of years).
We have started from the characterization of fault zone structure of carbonate/phyllosilicate rich faults showing that fault zone structure (localized vs. distributed) and deformation mechanisms are mainly influenced by the protolith lithology. The one-to-one comparison between fault zone structure mapped at the surface versus the one reconstructed by high-resolution aftershock locations defines an image of active carbonate-bearing faults consisting of parallel and interacting slipping segments extending for a width of about 1.5 km.
We have discovered that frictionally induced grain sensitive superplastic behaviour can account for the onset of dynamic weakening and also thermal decomposition occurs on carbonate faults during earthquake propagation.
For carbonate/phyllosilicate rich faults we have documented the long-term frictional weakness in décollements of tectonic wedges, the fast healing of calcite induced by the interplay of numerous physico-chemical processes, and seismic vs. aseismic creep controlled by mineralogy and fault fabric.
We have characterized systematic variations of the physical properties of experimental faults across the transition from stable sliding, slow- to fast- slip earthquakes.
Apart for earthquake phenomena, results from GLASS have potential impact on the energy field (fault and permeability, the role of fluid pressure in induced seismicity), environment (characterization of host rocks for radioactive waste and natural examples of CO2 geological storage) and landslides (frictional stability of large landslides in the Alps).
GLASS has been a fantastic opportunity for enhancing our research environment: for example several PhD and Post-Doc students have developed their training through research activities on the different scientific topics of the project and researchers from different countries have come to Roma to use BRAVA facilities and for a scientific exchange.