Earthquakes are among the most catastrophic and least predictable of all natural hazards, with a potential for dramatic loss of life, colossal economic damage, and destabilization of countries. They also represent a fundamentally challenging scientific problem, with a great potential for new discoveries. In the last 15 years high-resolution geophysical investigations have documented that faults accommodate deformation via a spectrum of fault slip behaviour spanning from aseismic slow slip to regular earthquakes. In addition, earthquake ruptures seem to be very complex and lithology, inherited structures and fluid overpressure are a primary explanation for these complexities.
The aim of this project is to unravel the lithological, structural and mechanical conditions that control active faulting in the Apennines. In particular we will work to: a) determine the role played by the inherited Jurassic structures in the distribution and geometry of active normal faults; b) accurately describe the lithologies involved in active deformation; c) characterize the physical properties and potential fault slip behaviour of these lithologies.
Our proposed geological work will be the first systematic study that will provide a reference geological framework to constrain the role of inherited Jurassic structures on the mechanics of active faulting of the Apennines, with invaluable insights for understanding earthquake processes. The new comprehensive characterization of the frictional properties of materials such as carbonates, marls, clays and basement rocks under different levels of fluid pressure will open the door for a significant advancement of knowledge with direct impact for the mechanics of slow earthquakes and induced seismicity. Finally, the multidisciplinary team to be assembled will be a perfect environment to train PhD and Post-docs researchers interested in fault mechanics.
Starting from the Irpinia 1980 earthquake, the first instrumentally monitored seismic sequence in the Apennines, with time the increasing number of seismic station within the Italian national seismic network has allowed to monitor seismic sequences with increasing details. These details have depicted complex active fault structures for both geometry (e.g. Valoroso et al., 2014) and rupture dynamics (e.g. Chiaraluce et al., 2017); quite often, inherited fault structures have been invoked to explain these complexities. Our proposed geological work will be the first systematic study that will provide a reference geological framework to constrain the role of inherited Jurassic structures on geometry and location of active faulting with invaluable insights for understanding earthquake processes. In particular geological mapping projects in the Tyrrhenian side of the Apennines seem to indicate an unexpected (in that it does not imply a re-utilization of the fault plane itself) conceptual link between Jurassic and active faults, which is firmly rooted in our knowledge of the Mesozoic paleogeography. Based on preliminary surveys, this mechanism could have been at work in the areas hit by recent earthquakes (e.g. Colfiorito 1997 and Amatrice-Norcia 2016).
The planned rock deformation experiments, in general will allow a comprehensive characterization of the rheological properties of the active faults of the Apennines with strong impact for all the physical models aimed at the characterization of earthquake nucleation and related hazard. In addition, some of the proposed experiments will allow the characterization of friction parameters under different levels of fluid pressure, from hydrostatic to near lithostatic. These types of experiments have never been developed due to experimental limitations. In fact so far similar experiments have been developed only for marble (Scuderi and Collettini 2016) using the only apparatus worldwide capable of testing frictional properties up to near lithostatic fluid pressure. This apparatus, named BRAVA (Collettini et al., 2014), has been designed and constructed by Prof. Collettini and his research group within the ERC projects GLASS. The new comprehensive characterization of the frictional properties of materials such as marls, clays or basement rocks under different levels of fluid pressure will open the door for a significant advancement of knowledge with direct implications for the mechanics of slow earthquakes that seem to occur within pressurized fault patches (e.g. Audet, P. and Burgmann R., 2014; Goswami and Barbot, 2018) or the induced seismicity mainly nucleating in the basement below the injection wells (Hornbach, 2015).
References
Audet, P. and Burgmann R., 2014, Nature, 510, 389-393.
Chiaraluce et al., 2017. Seismological Research Letters, doi: 10.1785/0220160221
Collettini et al., 2014. Int. Journal of Rock Mechanics, doi.org/10.1016/j.ijrmms.2013.12.005.
Goswami and Barbot, 2018, Scientific Reports, DOI:10.1038/s41598-018-24637-z.
Hornbach, M.J. et al., 2015, Nat. Comm., 6, 6728.
Scuderi M.M. and Collettini C. 2016. Scientific Reports, doi: 10.1038/srep24852.
Valoroso et al., 2014. Geology, doi:10.1130/G35071.1