Anna Maria Blumetti

Surface Faulting of the 6 April 2009 Mw 6.3 L’Aquila Earthquake in Central Italy

This paper documents evidence of surface faulting associated with the 6 April 2009 moderate-sized earthquake (ML 5.8, Mw 6.3) in the central Apennines of Italy, which caused major damage to the town of L’Aquila and its surroundings. Coseismic surface ruptures were mapped for a minimum distance of 2.6 km along the Paganica fault, a fault still poorly investigated relative to the other active faults nearby, which bound much wider range fronts. Surface rupture length (SRL) and maximum displacement parameters (2.6 km minimum and 10–15 cm, respectively) are in agreement with what is expected for an Mw 6.3 event in the Italian Apennines tectonic environment. Different viewpoints exist on the amount of SRL and the number of activated faults. We propose a pattern of sympathetic and secondary slip on an array of faults around the master seismogenic structure. Past seismicity and evidence for larger Holocene offsets on this and other capable faults nearby prove that the 2009 event is not a good reference event for assessing the seismic hazard of the region. Nevertheless, the 2009 L’Aquila earthquake once more confirmed the importance of detailed geological studies for a proper seismic hazard assessment, and it clearly illustrates the need to pay attention to moderate events and supposedly minor active faults. Indeed, this type of earthquake is rather frequent in the whole Mediterranean region and is potentially much more destructive than in the past, due to the expanding urban centers and infrastructures inside their epicentral regions and even right above the traces of capable faults.

Landslides Induced by Historical and Recent Earthquakes in Central-Southern Apennines (Italy): A Tool for Intensity Assessment and Seismic Hazard

Analysis of distribution of landslides (rock falls and coherent slides), induced by 12 moderate to strong earthquakes occurred in the last three centuries in Central–Southern Apennines, has permitted to investigate the relationship of their maximum distance versus magnitude and ESI epicentral intensity.

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.

Surface Faulting Hazard in Italy: Towards a First Assessment Based on the ITHACA Database

The Italian territory is characterized by a great number of capable faults (i.e., faults able to produce significant ruptures/deformations at or near the surface). However, the potential of tectonic surface rupture/deformation (Surface Faulting Hazard, SFH) is not properly considered in national seismic hazard maps and legislation. In this paper it is proposed an assessment of SFH in Italy based on the ITHACA database, where the shape and width along capable faults as well as maximum expected surface displacements are defined in function of the seismotectonic behaviour and the severity of maximum expected earthquake. The proposed assessment indicates where SFH is expected to be relevant. In this sense, it is an helpful tool for site selection of critical facilities but also for ordinary land planning. Of course, the evaluation of SFH at local scale in the setback areas requires a more detailed characterization through ad hoc seismotectonic and paleoseismic investigations.

Landslides Induced by the 1908 Southern Calabria: Messina Earthquake (Southern Italy)

Five hundred and two different testimonies of coseismic environmental effects of the 1908 Southern Calabria-Messina earthquake have been identified and catalogued, based on a careful screening of contemporary documents, i.e. technical and photographic reports, newspapers and other archive material. Out of the 348 independent occurrences, landslides are the most represented category with 150 cases (43 % of the whole set of effects). The area, which is prone to slope instability even without seismic triggering, due to its lithological characters and rugged topography, undergoes now a much higher seismic risk because of the unconcerned strong urban development of recent decades. So, the obtained scenario of landslides distribution triggered by the 1908 earthquake helps to evaluate the impact on this region of a 1908-like future event.