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On December 26, 2018 (2:19 UTC), during a volcanic eruption on the Mt. Etna eastern flank (Sicily, southern Italy), the largest instrumental earthquake ever recorded in the volcano ruptured the Fiandaca Fault, with epicenter between Fleri and Pennisi villages (hypocenter at ca. 300 m a. s. l., Mw 4.9). This was the mainshock of an earthquake swarm and it was accompanied by widespread surface faulting and extensive damage along a narrow belt near the fault trace. Few hours after the mainshock, an episodic aseismic creep event occurred along the Aci Platani Fault, a SE extension of the Fiandaca Fault, which caused several damages in the Aci Platani village. We surveyed and mapped the coseismic and aseismic ground ruptures, and collected structural data on their geometry, displacement, and fault zone fabric. We compared the mapped surface ruptures with topography, lithology, and morphology of the buried top of the sedimentary basement. We conclude that the geometry of the volcanic pile influenced the surface expression of faulting during the December 26, 2018 event. The top surface of the marly clay basement should be considered as a detachment surface for shallow sliding blocks. The earthquake occurred on top of a depression of the sedimentary basement forcing the sliding eastward, causing at surface the re-arrangement of the fault strand pattern and deformation style, switching from shear faulting to a tensile failure. The Fleri earthquake therefore provides an unprecedented dataset for 1) understanding active faulting in the European largest onshore volcano, 2) modeling its complex dynamics, and 3) contributing to a more refined surface faulting hazard assessment at Mt. Etna. Results from this investigation might be useful for characterizing capable faulting in similar volcano-tectonic settings worldwide.

Earthquake Environmental Effects (EEEs) such as surface faulting, landslides, liquefaction and tsunamis are widely distributed following strong seismic events and may account for a significant part of the overall damage. Here, we investigate EEEs generated by two earthquakes with different source parameters, both occurring along the Mexican subduction zone: the Sept. 8, 2017, Mw 8.2, moderate depth, normal fault, intraslab event; and the June 23, 2020, Mw 7.0, shallow depth, thrust fault, interface event. We document all the EEEs for each event, assign an intensity value using the Environmental Seismic Intensity (ESI-2007) scale, and derive the macroseismic fields. Finally, we compute the attenuation of intensity with distance and we compare it with other subduction zone earthquakes worldwide, demonstrating the repeatability of EEEs. This work represents the first application of the ESI-2007 scale to an intraslab earthquake and documents its wide applicability in different seismotectonic settings. We argue that EEEs provide useful information that should not be neglected in seismic hazard assessment procedures.

Ground effects have been an integral part of intensity (I) assessment since introduction of the first scale by de Rossi and Forel in 1883. However during the first half of this century an enormous amount of work has been devoted to improving I scales through a detailed classification of the different types of buildings and expected damage. As an extreme culmination of this tendency, the recent up-dated EMS 92 macroseismic scale completely ignores ground effects, only listing them in a short Appendix. Although this approach is reasonable for densely urbanized areas, it does not reflect the full meaning of the I parameter, it docs not work for I assessment in the highest degrees of the scales, it is unsuitable in remote areas and cannot be used for comparison of historical events and seismic hazard evaluation in areas affected by strong events with return periods longer than the historical records. On the other hand, worldwide studies on the empirical relations between seismic parameters and ground effects demonstrate that, even if type and relevance of surface effects strongly depend on the local geomorphological setting, their definition allows a realistic estimation of the earthquake size. In this paper these relations are briefly discussed and preliminary proposals are given for the better use of ground effects in I assessment.

On 21 August 2017, a shallow earthquake of Md 4.0 struck the CasamicciolaTerme village in the north of Ischia volcanic island (Italy). It caused two fatalities and heavy damage in a restricted area of a few square kilometers. 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. Soon after the 2017 mainshock we surveyed the epicentral area to collect data on the coseismic ground effects, recording more than 100 geological field observations. Mapped effects define a belt which closely follows the trace of the Casamicciola E-W-trending normal fault system, bounding the northern slope of Mt. Epomeo, previously known as a Latest Pleistocene to Holocene normal fault with a slip rate of ~3:0 cm=yr. We found significant evidence for coseismic surface faulting, testified by a main alignment of ruptures for a 2 km end-to-end length and normal dip-slip displacement of 1-3 cm. The geometry and regularity of the structural pattern, together with constant kinematics of the coseismic ruptures with the north side down, strongly suggest a primary tectonic origin for the mapped ruptures and strongly supports an E-W normal-faulting focal mechanism for the 2017 Casamicciola earthquake.Macroseismic information supports the notion that previous historical events also had a similar style of faulting.

The earthquake environmental effects (EEEs) around the epicentral area of the Pohang earthquake (Mw-5.4) that occurred on 15 November 2017 have been collected and classified using the Environmental Seismic Intensity Scale (ESI-07 scale) proposed by the International Union for Quaternary Research (INQUA) focus group. The shallow-focus 15 November Pohang earthquake did not produce any surface rupture, but caused extensive secondary environmental effects and damage to life-line structures. This earthquake was one of the most damaging earthquakes during the instrumental seismic era of the Korean Peninsula. The EEEs included extensive liquefaction, ground cracks, ground settlement, localized rockfall, and variation of the water table. The main objective of this paper was to carry forward a comparative assessment of the Pohang earthquake&rsquo, s intensity based on traditional macroseismic scales and the ESI-07 scale. With that objective, this study will also make a substantial contribution to any future revision of the ESI-07 scale, which mostly comprises case studies from Europe and South America. The comparison of the ESI-07 scale with traditional intensity scales similar to the intensity scale used by the Korean Meteorological Administration for the epicentral areas showed 1&ndash, 2-degree differences in intensity. Moreover, the ESI scale provided a clearer picture of the intensity around the epicentral area, which is mostly agricultural land with a lack of urban units or buildings. This study urges the integration of the traditional and ESI-07 scale for such small magnitude earthquakes in the Korean Peninsula as well as around the world in future. This will predict seismic intensity more precisely and hence provide a more-effective seismic hazard estimation, particularly in areas of low seismic activity. The present study will also provide a useful and reliable tool for the seismic hazard assessment of similar earthquakes around the study area and land-use planning at a local scale considering the secondary effects.

The main objective of this paper was to introduce the Environmental Seismic Intensity scale (ESI), a new scale developed and tested by an interdisciplinary group of scientists (geologists, geophysicists and seismologists) in the frame of the International Union for Quaternary Research (INQUA) activities, to the widest community of earth scientists and engineers dealing with seismic hazard assessment. This scale defines earthquake intensity by taking into consideration the occurrence, size and areal distribution of earthquake environmental effects (EEE), including surface faulting, tectonic uplift and subsidence, landslides, rock falls, liquefaction, ground collapse and tsunami waves. Indeed, EEEs can significantly improve the evaluation of seismic intensity, which still remains a critical parameter for a realistic seismic hazard assessment, allowing to compare historical and modern earthquakes. Moreover, as shown by recent moderate to large earthquakes, geological effects often cause severe damage''; therefore, their consideration in the earthquake risk scenario is crucial for all stakeholders, especially urban planners, geotechnical and structural engineers, hazard analysts, civil protection agencies and insurance companies. The paper describes background and construction principles of the scale and presents some case studies in different continents and tectonic settings to illustrate its relevant benefits. ESI is normally used together with traditional intensity scales, which, unfortunately, tend to saturate in the highest degrees. In this case and in unpopulated areas, ESI offers a unique way for assessing a reliable earthquake intensity. Finally, yet importantly, the ESI scale also provides a very convenient guideline for the survey of EEEs in earthquake-stricken areas, ensuring they are catalogued in a complete and homogeneous manner

The application of the Environmental Seismic Intensity (ESI) scale 2007 to moderate and strong earthquakes, in different geological context all over the word, highlights the importance of Earthquake Environmental Effects (EEEs) for the assessment of seismic hazards. This Special Issue “New Perspectives in the Definition/Evaluation of Seismic Hazard through Analysis of the Environmental Effects Induced by Earthquakes” presents a collection of scientific contributions that provide a sample of the state-of-the-art in this field. Moreover the collected papers also analyze new data produced with multi-disciplinary and innovative methods essential for development of new seismic hazard models.

The aim of this study is to describe the modifications of the built environment that have occurred in 36 years following the Irpinia-Basilicata, 1980 earthquake. In particular, especially in the villages of the epicentral area, changes in the urban and territorial setting have been examined, as well as the consequences of ground effects that have influenced the choices of reconstruction, both in situ, and far from the original historical centers. The November 23, 1980 Irpinia-Basilicata earthquake (Mw = 6.9; Io = X MCS; Io = X ESI-07), killing 3000 people, hit 800 localities over a large area of Southern Italy; 75,000 houses totally collapsed and 275,000 were badly damaged. The earthquake induced primary and secondary environmental effects, over all slope movements. The total amount of surface faulting was 40 km in length with the maximum displacement of 100 cm; the total area affected by slope movements was estimated to be about 7400 km2, with 200 landslides classified. One of the largest landslides damaged Calitri village, in Avellino province. We have examined, as case histories, the reconstruction of Calitri and San Mango sul Calore villages, that were affected by severe landslides and were rebuilt in situ; we have also studied Conza della Campania that was reconstructed far from the original location. In the so-called Anthropocene age, the role of technical experts both in the built environment and in the social and ethical context is extremely important, for rebuilding the villages destroyed by earthquakes, especially in respect of the people resilience.

Viene illustrta brevemente la storia dei terremoti che hanno colpito la città di Napoli, a partire dal Xv secolo sino al XX secolo.

The 23 July 1930 earthquake (MS=6.7) in the Southern Apennines (Italy) was a catastrophic event that produced many effects such as surface faulting, fractures, landslides, settlements, hydrological changes, variations in chemical/physical activity related to the volcanic and/or thermal zones and also acoustic and optical phenomena. It is the first great earthquake of the twentieth century that was studied, thanks to the hydrological monitoring network of the Italian Hydrographic Survey (IHS) set up from 1925 to 1929. For this earthquake we analysed the initial IHS hydrometric and pluviometric data, looking for significant anomalies in springs, water wells and mountain streams. Hydrological data relative to rivers, springs and water wells indicate that some changes can be correlated with the earthquake: a post-seismic excess discharge in some streams, pre- and co-seismic decreases in stream flows and water levels in wells, pre- and post-seismic increases in discharges. The pre- and co-seismic stresses and the tectonic deformations were studied in order to find a possible model of interaction between stress state and hydrological variations. The anomalies found in this work can be considered "rebound anomalies", which are the most common precursor reported by many authors and related to increases in porosity and permeability caused by the fracturing that precedes an earthquake. An estimation of the total excess discharge (0.035 km3) caused by the MS=6.7 Irpinia earthquake is consistent with the excess discharge of about 0.01 km3 determined for the Mw=6.9 Loma Prieta earthquake.

A high-resolution (IKB-Seistec) seismic survey calibrated with gravity-core data, off the Amalfi coast, a rocky coastal area on the southern side of the Sorrento Peninsula (Italy), documents the internal stratigraphic architecture of a series of small fan-deltas that develop at the mouth of major bedrock streams. The fan-delta system mostly postdates the Plinian eruption of Vesuvius of AD 79 and displays various phases of development associated with periods of high sediment supply from the adjacent river basins. During these periods landscape-mantling loose pyroclastic deposits (mostly air-fall tephra from Vesuvius) were quickly eroded and delivered to the continental shelf by sheet wash and flash flood events. Depositional processes on the foresets were dominated by sediment gravity flows originating from hyperpycnal river flow and pyroclastic fall deposits. This in turn created favourable conditions for sea-floor instability, soft sediment failure, slumping and sliding, which characterize the deltaic stratigraphic architecture. The intermittently increased sediment yield during the various phases of the evolution of the fan-delta system was probably influenced also by the morphoclimatic regime. This may have resulted in varying rates of progradation of the delta foresets, tentatively correlated with the main climatic oscillations of the last 2000 years. The Amalfi fan-delta system represents a small-scale analogue for larger flood-dominated fan-deltas of the world and may be regarded as a useful example for a better understanding of inner-shelf, mixed siliciclastic-volcaniclastic fan-delta systems in the stratigraphic record. © The Geological Society of London 2009.

Documentary source materials are essential for retrospective reconstruction of flood events occurring in past centuries. This paper presents methods of research and archiving of historical data from the 16th century to the present. The quality and completeness of the various original sources were evaluated and carefully analysed in their historical context, to avoid serious mistakes. Systematic investigation of about 3000 documents, mainly found in national State Archives and libraries, allows us to identify and localize at least 106 flood events occurring along the Amalfi coast (southern Italy) for five centuries between the years 1500 and 2000. The collected data provide useful details on flood dynamics, size of flooded areas, flood duration, damage level, number of victims and induced geological effects. When available in sufficient quantity, the flood data allow determination of very useful parameters such as the severity class, to identify large floods and their recurrence interval.

Guatemala is one of the most seismically active countries of Central America. It has suffered several dramatic earthquakes during the last century, the most destructive of which was the event associated with the Motagua fault, occurred on 4, February 1976, that caused 23,000 deaths, and 77,200 injuries. Noteworthy were also the coseismic geological effects, either directly linked to the earthquake source, such as a remarkable displacement along a 230 km long strike-slip fault, or caused by the ground shaking, such as 50,000 landslides, numerous liquefaction phenomena, ground cracks and ground deformation over an area of about 18,000 km2. In spite of this, the estimated intensity was relatively low (Imax = IX MM, only in few localities). For this reason, in order to achieve a better definition of seismic hazard, we have conducted a re-evaluation of the 1976 earthquake taking into account the environmental effects that have contributed substantially to the dramatic level of recorded impact, both in terms of loss of human life and damage affecting housing and infrastructures. The analysis of primary and secondary effects has permitted a better evaluation of seismic intensity in 24 localities that were hit by the earthquake and allowed for establishing a new epicentral Intensity, characterized by XI ESI. The recalculated seismic intensity is consequently two degrees higher than previous estimates and definitely more consistent with the scenario of the actual damage caused by the earthquake.

Moderate to strong crustal earthquakes are generally accompanied by a distinctive pattern of coseismic geological phenomena, ranging from surface faulting to ground cracks, landslides, liquefaction/compaction, which leave a permanent mark in the landscape. Therefore, the repetition of surface faulting earthquakes over a geologic time interval determines a characteristic morphology closely related to seismic potential. To support this statement, the areal distribution and dimensions of effects of recent historical earthquakes in the Southern Apennines are being investigated in detail. This paper presents results concerning the 26 July 1805 earthquake in the Molise region, (I =X MCS, M = 6.8), and the 23 November 1980 earthquake in the Campania and Basilicata regions (I =XM SK,Ms = 6.9). Landslide data are also compared with two other historical earthquakes in the same region with similar macroseismic intensity. The number of significant effects (either ground deformation or hydrological anomalies) versus their minimum distance from the causative fault have been statistically analyzed, finding characteristic relationships. In particular, the decay of the number of landslides with distance from fault follows an exponential law, whereas it shows almost a rectilin- ear trend for liquefaction and hydrological anomalies. Most effects fall within the macroseismic area, landslides within intensity V to VI, liquefaction effects within VI and hydrological anomalies within IV MCS/MSK, hence at much larger distances. A possible correlation between maximum distance of effects and length of the reactivated fault zone is also noted. Maximum distances fit the envelope curves for Intensity and Magnitude based on worldwide data. These results suggest that a careful examination of coseismic geological effects can be important for a proper estimation of earthquake parameters and vulnerability of the natural environment for seismic hazard evaluation purposes.

The study of hydrological variations in the watersheds of seismic areas can be useful in order to acquire a new knowledge of the mechanisms by which earthquakes can produce hydrological anomalies. Italy has the availability of many long historical series both of hydrological parameters and of seismological data, and is an ideal laboratory to verify the validity of theoretical models proposed by various authors. In this work we analyse the hydrological anomalies associated with some of the big earthquakes that occurred in the last century in the southern Apennines: 1930, 1980 and 1984. For these earthquakes we analysed hydrometric and pluviometric data looking for significant anomalies in springs, water wells and mountain streams. The influence of rainfalls on the normal flows of rivers, springs and wells has been ascertained. Also, the earthquake of 1805, for which a lot of hydrological perturbations have been reported, is considered in order to point out effects imputable to this earthquake that can be similar to the effects of the other big earthquakes. The considered seismic events exhibit different modes of energy release, different focal mechanisms and different propagation of effects on the invested areas. Furthermore, even if their epicentres were not localised in contiguous seismogenetic areas, it seems that the hydrological effects imputable to them took place in the same areas. Such phenomena have been compared with macroseismic fields and transformed in parameters, in order to derive empirical relationships between the dimensions of the event and the characteristics of the hydrological variations. The results of this work point to a close dependence among hydrological anomalies, regional structures and fault mechanisms, and indicate that many clear anomalies have been forerunners of earthquakes. In 1993, the Naples Bureau of the Hydrographic National Service started the continuous monitoring of hydrologic parameters by a network of automatic stations and transmission in real time; presently 7 acquifers are under control in which also pH, T , salinity, electrical conductivity, dissolved oxygen are measured. We envisage to increase the number of monitoring sites and controlled parameters.

This paper both describes and discusses landslides and other ground effects induced by the September–October 1997 seismic sequence, which struck the Umbria and Marche regions (Central Italy). Three main events occurred on 26 September at 00:33 and 09:40 GMT, and 14 October with magnitude M w equal to 5.8, 6.0 and 5.4, respectively; furthermore hundreds of minor but significant events were also recorded. The authors examined an area of some 700 km 2 around the epicentre (Colfiorito). Primary and secondary effects were observed, including surface faulting phenomena, landslides, ground fractures, compaction and various hydrological phenomena. Surface evidence of faulting reactivation was found along the well-known capable faults, to a total length of ca. 30 km. Landslides, which were the most recurrent among the phenomena induced, consisted mainly of rock falls and subordinately of rotational and translational slides, which were generally mobilised by the inertia forces during the seismic motion. The percentage of reactivated old landslides decreased as the distance from the epicentral zone increased; a similar decrease had been observed for the 1980 Irpinia earthquake (Southern Italy). The ground fracture distribution was consistent with the regional structural setting and the general pattern of macroseismic field. Numerous episodes of hydrological changes were observed within the most severely damaged area. All this evidence confirms the relevance of the study of ground surface effects for achieving a more complete evaluation of seismic hazard.

The September–October 1997 seismic sequence in the Umbria–Marche regions of Central Italy (main shocks on September 26, Mw 5.7 and 6.0, and on October 14, Mw 5.6) left significant ground effects, which were mainly concentrated in the Colfiorito intermountain basin. These effects included surface faulting, ground cracks and settlements, rock falls, slides, hydrological and gas anomalies. The distribution and size of ground effects has proved useful for (1) defining the epicentral area and the location of the causative fault; (2) complementing the intensity pattern from damage distribution (this can be very useful in poorly inhabited zones); (3) integrating or testing the intensity assessment of many historical events, in order to obtain a better evaluation of the magnitude from intensity data. Of special interest was the observation of surface ruptures generated along segments of a system of normal faults already mapped as capable, with end-to-end lengths of 12 km and maximum displacements of 8 cm. Many pieces of evidence confirm that coseismic slip was not a secondary, gravity-induced, phenomenon, but had a tectonic origin. Detailed descriptions of surface faulting for moderate earthquakes are not common, being easily missed or misinterpreted; however, in this paper we emphasize that surface faulting due to the 1997 event can be used to infer the threshold magnitude for surface faulting in Central Apennines, allowing to calibrate palaeoearthquake size from fault offsets as seen in trench investigations.

A reconstruction of historical floods occurred along the Amalfi coast, during the last five centuries is presented. The analysis of historical sources allowed to achieve a chronological reconstruction of more than 100 floods, four of which classified as catastrophic events. In this task, the level of information was decisive to carry out space-time identification, estimate the affected area and define the type of damage to the structures, and the environment (e.g. mud flow, debris flow, rock falls, shoreline progradation, fan deltas), which may be relevant for the recognition of similar events within the geologic record. The magnitude of the events was finally estimated, taking into account the size of the areas affected by flooding as well as the type of effects induced on the urban and physical environment and the recurrence intervals. © Springer-Verlag Berlin Heidelberg 2013.

Most relevant macroseismic and instrumental data concerning past and current seismic activity of the Potentino, southern Italy, have been collected in order to study the seismic behaviour of this area. Ten among the most important recent and historical earthquakes occurred in the area from 1826 to 1990 have been studied by means of macroseismic methodologies; macroseismic fields for all the events indicate a general isoseismal lengthening in the direction of the Apennines chain (northwest-southeast), a rapid attenuation of intensity westward of the studied area and a strong propagation eastwards; this configuration is strongly dependent on the source mechanisms of the seismic events and the geological dishomogeneities of the concerned areas. As regards earthquakes which have been instrumentally recorded in the Campania-Basilicata area from 1980 to 1991, more than 1300 accurate hypocentral locations have been computed for events with M D ⩾ 2.5, using data from Osservatorio Vesuviano (O.V.) and Istituto Nazionale di Geofisica (I.N.G.) seismic networks. Special emphasis is put on the Potenza May 5, 1990 earthquake ( M S = 5.4 NEIC—National Earthquake Information Center; I = VII MSK) which was the strongest recent event in the area and was felt in a large sector of southern Italy. As regards the seismic sequence following this event, about 110 aftershocks with M D ⩾ 1.9 have been located very close to the town of Potenza, northeast of it, with a clustering-type space distribution. The occurrence of the events is strongly time concentrated, in so defining a main shock-aftershocks typical sequence. Moreover, the macroseismic investigation of the main event has allowed to map out isoseismal lines bounding VII, VI, V and IV MSK areas; the isoseismals pattern shows that attenuation and amplification of intensity are observed in the same areas as for the previous events. Beginning from May 26, 1991 an increase of seismicity, initiated by an earthquake of M L = 4.7 NEIC and I = VI-VII MSK was observed nearly in the same area as the 1990 sequence. Accurate locations of 84 events with M D ⩾ 1.9 have been computed. However, this sequence seems to have a slightly different character from the 1990 one, in that events are scattered in time and seismic energy release is comparable to a swarm-type seismic sequence. As regards the previous sequences, fault plane solutions for the highest-magnitude events and for appropriate groups of events have been worked out; the mechanisms indicate normal faulting motion with T axes oriented orthogonal to the Apenninic chain. In conclusion, detailed analyses on the historical and recent seismicity of the Potentino area and adjacent ones have allowed to identify at least four seismogenic zones which show activity with different features. Such zoning represents a contribution to the seismic hazard assessment in the Southern Apennines on a regional scale.

On Oct. 4th, 1983 the area of Phlegraean Fields, near Naples (Southern Italy) was shaked by an earthquake of magnitude (M L) 4.0 that caused some damage in the town of Pozzuoli and its surroundings. This seismic event was the largest one recorded during the recent (1982–84) inflation episode occurred in the Phlegraean volcanic area, and a detailed macroseismic reconstruction of the event was carried out. Failing macroseismic data on other earthquakes occurred in Phlegraean Fields, the attenuation law of the intensity as a function of the distance as obtained for the Oct. 4th earthquake was compared with those obtained for other volcanic areas in central Italy —i.e., Tolfa, Monte Amiata — in order to check the reliability of the results obtained for Phlegraean Fields. The Blake's model of the earthquake of Oct. 4th, 1983 does not agree with the experimental data because isoseismals contain areas larger than those shown by the model. This result has been interpreted as an effect of energy focusing due to a reflecting layer 6–8 km deep.

In this paper some extreme flooding events occurred in the Campania Region, particularly in the Salerno province since the XVI century, and in the Somma-Vesuvius volcanic complex since the beginning of the XX century, have been analyzed. Through a multidisciplinary approach based on detailed bibliographic and archival documents investigation, besides geologic-geomorphologic analyses, in GIS environment, the landslide distribution and frequency in the last centuries, inside these two areas, has been examined, jointly with the urbanization evolution for the Vesuvius area. In particular, seven flood events, the 1581, 1588, 1773, 1899, 1910, 1924 and the 1954 floods occurred in the Salerno province, have been studied in detail; while the alluvial phenomena occurred in the Somma-Vesuvius district, repeatedly affected by disastrous flood events, and occurred from 1906 to 2011, have been reported. Although this study is not exhaustive, it aims to contribute, illustrating a methodology for data searching and analyzing, to a correct assessment and reduction of hydrogeological risk in the Campania region.