ALBERT

Description: We provide a database that embodies more than 7000 punctual observations of the coseismic surface geological effects following the 30 October 2016 Mw 6.5 earthquake that hit central Italy. This earthquake caused widespread surface ruptures over a 〉400 km2-wide mountainous area. The Open EMERGEO Working Group, originated by the collaboration of several European geological survey teams coordinated by the Istituto Nazionale di Geofisica e Vulcanologia, involved about 130 researchers to perform detailed geological field surveys in the epicentral region. These observations mostly include accurate description of the geometry and kinematics of ground breaks caused by primary surface faulting, and subordinately by landslides due to shaking. The database consists of georeferenced records containing both numeric and string fields in the form of a suitable .txt file.

Description: We provide a database of the coseismic surface ruptures produced by the 21 August 2017 Md 4.0 earthquake that struck the Casamicciola Terme village in the north of Ischia volcanic island (Italy). Despite its small size, the earthquake caused two fatalities and heavy damages in a restricted area of a few square kilometers. The shallow hypocentral depth of the earthquake caused a significant coseismic surface faulting, testified by a main alignment of ruptures mapped for a 2 km end-to-end length along the Casamicciola E-W trending normal fault system, bounding the northern slope of Mt. Epomeo. Casamicciola Terme has been recurrently destroyed in the last centuries by similar volcano-tectonic earthquakes (1762, 1767, 1796, 1828, 1881, and 1883). After the catastrophic 1883 Casamicciola event (2343 casualties), this is the first heavy damaging earthquake at Ischia that provides, for the first time, the opportunity of integrating historical seismicity, macroseismic observations, instrumental information, and detailed mapping of coseismic geological effects. We performed a detailed field surveys in the epicentral region of the 21 August earthquake to describe the ruptures geometry and kinematics of the seismogenetic fault responsible of the earthquake with the aim of contributing to the seismic hazard evaluation and land use planning in the Ischia island, one of the most crowded touristic destinations worldwide. Summarizing our study of ground effects for the 21 August 2017 earthquake is important for improving knowledge on surface earthquake in the volcanic area and contributing to complete the gap of empirical scaling relating to the surface-faulting mechanism due to small-size or moderate earthquakes in volcano-tectonic framework. The collected field observations result in a dataset of 88 georeferenced records describing coseismic ruptures/fractures by features as ID number, time of sample collection, location (latitude, longitude, elevation), type of rupture, type of affected substratum, attitude (dip angle, dip direction, strike), surface offset (opening, throw, strike slip, net slip), kinematics, slip vector attitude, width of the deformation zone.

Description: We provide a database of the coseismic surface ruptures produced by the 26 December 2018 Mw 4.9 earthquake that struck the eastern flank of Mt. Etna (southern Italy), the largest active volcano in Europe. Despite its small size, this shallow earthquake caused an impressive system of coseismic surface ruptures extending about 8.5 km, along the trace of the NNW-trending active Fiandaca Fault. We performed detailed field surveys were performed in the epicentral region to describe the ruptures geometry and kinematics. These exhibit a dominant right-oblique sense of slip with coseismic displacement peaks of 0.35 m. The Fiandaca Fault is part of a complex active faults system affecting the eastern flank of Mt. Etna. Its seismic history indicates a prominent surface-faulting potential, so our study is essential for unravelling the seismotectonics of shallow earthquakes in volcanic settings, and contributes updating empirical scaling laws relating moderate-sized earthquakes and surface faulting. The collected observations have been parsed and organized in a concise database consisting of 874 homogeneous georeferenced records. The main features describing the coseismic ruptures are the following: ID, time of sample collection, location (latitude, longitude, elevation), type of rupture, type of affected substratum, attitude (dip angle, dip direction, strike), surface offset (opening, throw, strike slip, net slip), kinematics, slip vector attitude, width of the deformation zone.

Description: The city of Naples (Campanian region, Southern Italy) has been hit by the strongest earthquakes located inside the seismogenic areas of the Southern Apennines, as well as by the volcano-tectonic earthquakes of the surrounding areas of the Campi Flegrei, Ischia and Vesuvius volcanic districts. An analysis of the available seismic catalogues shows that in the last millennium, more than 100 earthquakes have struck Naples with intensities rating I to III on the Mercalli–Cancani–Sieberg (MCS) scale over the felt level. Ten of these events have exceeded the damage level, with a few of these possessing an intensity greater than VII MCS. The catastrophic earthquakes of 1456 (I0 = XI MCS), 1688 (I0 = XI MCS) and 1805 (I0 = X MCS) occurred in the Campania–Molise Apennines chain, produced devastating effects on the urban heritage of the city of Naples, reaching levels of damage equal to VIII MCS. In the 20th century, the city of Naples was hit by three strong earthquakes in 1930 (I0 = X MCS), 1962 (I0 = IX MCS) and 1980 (I0 = X MCS), all with epicenters in the Campania and Basilicata regions. The last one is still deeply engraved in the collective memory, having led to the deaths of nearly 3000 individuals and resulted in the near-total destruction of some Apennine villages. Moreover, the city of Naples has also been hit by ancient historical earthquakes that originated in the Campanian volcanic districts of Campi Flegrei, Vesuvio and Ischia, with intensities up to VII–VIII MCS (highest in the Vesuvian area). Based on the intensity and frequency of its past earthquakes, the city of Naples is currently classified in the second seismic category, meaning that it is characterized by “seismicity of medium energy”. In this paper, we determine the level of damage suffered by Naples and its monuments as a result of the strongest earthquakes that have hit the city throughout history, highlighting its repetitiveness in some areas. To this aim, we reconstructed the seismic history of some of the most representative urban monuments, using documentary and historical sources data related to the effects of strong earthquakes of the Southern Apennines on the city of Naples. The ultimate purpose of this study is to perform a seismic macro-zoning of the ancient center of city and reduce seismic risk. Our contribution represents an original elaboration on the existing literature by creating a damage-density map of the strongest earthquakes and highlighting, for the first time, the areas of the city of Naples that are most vulnerable to strong earthquakes in the future. These data could be of fundamental importance to the construction of detailed maps of seismic microzones. Our study contributes to the mitigation of seismic risk in the city of Naples, and provides useful advice that can be used to protect the historical heritage of Naples, whose historical center is a UNESCO World Heritage site.

Description: We report a geophysical study across an active normal fault in the Southern Apennines. The surveyed area is the “Il Lago” Plain (Pettoranello del Molise), at the foot of Mt. Patalecchia (Molise Apennines, Southern Italy), a small tectonic basin filled by Holocene deposits located at the NW termination of the major Quaternary Bojano basin structure. This basin, on the NE flank of the Matese Massif, was the epicentral area of the very strong 26 July, 1805, Sant’Anna earthquake (I0 = X MCS, Mw = 6.7). The “Il Lago” Plain is bordered by a portion of the right-stepping normal fault system bounding the whole Bojano Quaternary basin (28 km long). The seismic source responsible for the 1805 earthquake is regarded as one of the most hazardous structures of the Apennines; however, the position of its NW boundary of this seismic source is debated. Geological, geomorphological and macroseismic data show that some coseismic surface faulting also occurred in correspondence with the border fault of the “Il Lago” Plain. The study of the “Il Lago” Plain subsurface might help to constrain the NW segment boundary of the 1805 seismogenic source, suggesting that it is possibly a capable fault, source for moderate (Mw 〈 5.5) to strong earthquakes (Mw ≥ 5.5). Therefore, we constrained the geometry of the fault beneath the plain using low-frequency Ground Penetrating Radar (GPR) data supported by seismic tomography. Seismic tomography yielded preliminary information on the subsurface structures and the dielectric permittivity of the subsoil. A set of GPR parallel profiles allowed a quick and high-resolution characterization of the lateral extension of the fault, and of its geometry at depth. The result of our study demonstrates the optimal potential of combined seismic and deep GPR surveys for investigating the geometry of buried active normal faults. Moreover, our study could be used for identifying suitable sites for paleoseismic analyses, where record of earthquake surface faulting might be preserved in Holocene lacustrine sedimentary deposits. The present case demonstrates the possibility to detect with high accuracy the complexity of a fault-zone within a basin, inferred by GPR data, not only in its shallower part, but also down to about 100 m depth.

Description: This paper aims to present, through a photographic reportage, the current state of rebuilding of the most devastated villages by the earthquake that hit the Southern Italy on 23 November 1980, in Irpinia-Basilicata. The earthquake was characterized by magnitude Ml = 6.9 and epicentral intensity I0 = X MCS. It was felt throughout Italy with the epicenter in the Southern Apennines, between the regions of Campania and Basilicata that were the most damaged areas. About 800 localities were serious damaged; 7,500 houses were completely destroyed and 27,500 seriously damaged. The photographic survey has been done in 23 towns during the last five years: Castelnuovo di Conza, Conza della Campania, Laviano, Lioni, Santomenna, Sant’Angelo dei Lombardi, Balvano, Caposele, Calabritto and the hamlet of Quaglietta, San Mango sul Calore, San Michele di Serino, Pescopagano, Guardia dei Lombardi, Torella dei Lombardi, Colliano, Romagnano al Monte, Salvitelle, Senerchia, Teora, Bisaccia, Calitri and Avellino. Forty years after the 1980 earthquake, the photographs show villages almost completely rebuilt with modern techniques where reinforced concrete prevails. Only in few instances, the reconstruction was carried out trying to recover the pre-existing building heritage, without changing the original urban planning, or modifying it. We argue that this photography collection allows to assess the real understanding of the geological information for urban planning after a major destructive seismic event. Even more than this, documenting the rebuilding process in a large epicentral area reveals the human legacy to the natural landscape, and our ability, or failure, to properly interpret the environmental fate of a site.

Description: Sediments infilling in intermontane basins in areas with high seismic activity can strongly affect ground-shaking phenomena at the surface. Estimates of thickness and density distribution within these basin infills are crucial for ground motion amplification analysis, especially where demographic growth in human settlements has implied increasing seismic risk. We employed a 3D gravity modeling technique (ITerative RESCaling—ITRESC) to investigate the Fucino Basin (Apennines, central Italy), a half-graben basin in which intense seismic activity has recently occurred. For the first time in this region, a 3D model of the Meso-Cenozoic carbonate basement morphology was retrieved through the inversion of gravity data. Taking advantage of the ITRESC technique, (1) we were able to (1) perform an integration of geophysical and geological data constraints and (2) determine a density contrast function through a data-driven process. Thus, we avoided assuming a priori information. Finally, we provided a model that honored the gravity anomalies field by integrating many different kinds of depth constraints. Our results confirmed evidence from previous studies concerning the overall shape of the basin; however, we also highlighted several local discrepancies, such as: (a) the position of several fault lines, (b) the position of the main depocenter, and (c) the isopach map. We also pointed out the existence of a new, unknown fault, and of new features concerning known faults. All of these elements provided useful contributions to the study of the tectono-sedimentary evolution of the basin, as well as key information for assessing the local site-response effects, in terms of seismic hazards.