Paolo Galli

Low slip rates and multimillennial return times for Mw 7 earthquake faults in southern Calabria (Italy)

The Calabrian Arc is the epicentral region of one third of the strongest earthquakes of Italy (Mw ≥ 7.0). These are confined within a narrow peninsula which is the emerging portion of a slab-related accretionary wedge, and all occurred in the past four centuries. Therefore, here more than anywhere in Italy, historical seismicity alone is not sufficient for seismic hazard assessment. We carried out geological and paleoseismological studies in southern Calabria that allowed characterizing the seismogenic behavior of the Cittanova fault which was responsible for one of the most catastrophic earthquakes to ever occur in Europe, the Mw 7.0 5 February 1783 event. We have found out conclusive evidence for four Holocene earthquakes prior to 1783, with a recurrence time longer (~3.2 kyr) than the other Apennine faults (0.3–2.4 kyr). We have also estimated a robust slip rate for the late Upper Pleistocene (0.6 mm/yr) and an extension rate (0.4 mm/yr) that could reflect the residual back-arc opening of the Tyrrhenian Basin.

Quaternary geology and paleoseismology in the Fucino and L’Aquila basins

This 2 days-long field trip aims at exploring field evidence of active tectonics, paleoseismology and Quaternary geology in the Fucino and L’Aquila intermountain basins and adjacent areas, within the inner sector of Central Apennines, characterized by extensional tectonics since at least 3 Ma. Each basin is the result of repeated strong earthquakes over a geological time interval, where the 1915 and 2009 earthquakes are only the latest seismic events recorded respectively in the Fucino and L’Aquila areas. Paleoseismic investigations have found clear evidence of several past earthquakes in the Late Quaternary to Holocene period. Active tectonics has strongly imprinted also the long-term landscape evolution, as clearly shown by numerous geomorphic and stratigraphic features. Due to the very rich local historical and seismological database, and to the extensive Quaternary tectonics and earthquake geology research conducted in the last decades by several Italian and international teams, the area visited by this field trip is today one of the best studied paleoseismological field laboratories in the world. The Fucino and L’Aquila basins preserve excellent exposures of earthquake environmental effects (mainly surface faulting), their cumulative effect on the landscape, and their interaction with the urban history and environment. This is therefore a key region for understanding the role played by earthquake environmental effects in the Quaternary evolution of actively deforming regions, also as a major contribution to seismic risk mitigation strategies.

Testing geomorphic signal of active normal faulting: The case of the Cittanova Fault (Calabria, southern Italy): Testing geomorphic signal of active normal faulting (Cittanova Fault)

Extracting tectonic signals from the landscape is an important challenge for constraining the style and rate of deformation associated with active faults, especially where their displacement history cannot be independently determined. Based on previous paleoseismological data coupled with new geomorphological field work and C dating of geomorphic markers, we analysed the geomorphic signal of the along-strike differential throw of the Cittanova Fault in southern Calabria (Italy), the recent activity of which is already well documented and constrained. Through DTM-derived stream power law parameters (SL and χ), we provide evidence of drainage network disequilibrium and reorganization in response to fault growth and deformation style. Furthermore, a methodological test of the reliability of the χmetric as a proxy for the differential throw along the strike of active normal faults provided good preliminary results, consistent with a strong inverse linear correlation with fault throw. Copyright