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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.

Readily available interferometric data (InSAR) of the coseismic deformation field caused by recent seismic events clearly show that major earthquakes produce crustal deformation over wide areas, possibly resulting in significant stress loading/unloading of the crust. Such stress must be considered in the evaluation of seismic hazards of nuclear power plants (NPP) and, in particular, for the potential of surface slip (i.e., probabilistic fault displacement hazard analysis - PFDHA) on both primary and distributed faults. In this study, based on the assumption that slip on pre-existing structures can represent the elastic response of compliant fault zones to the permanent co-seismic stress changes induced by other major seismogenic structures, we propose a three-step procedure to address fault displacement issues and consider possible influence of surface faulting/deformation on vibratory ground motion (VGM). This approach includes: (a) data on the presence and characteristics of capable faults, (b) data on recognized and/or modeled co-seismic deformation fields and, where possible, (c) static stress transfer between source and receiving faults of unknown capability. The initial step involves the recognition of the major seismogenic structures nearest to the site and their characterization in terms of maximum expected earthquake and the time frame to be considered for determining their “capability” (as defined in the International Atomic Energy Agency - IAEA Specific Safety Guide SSG-9). Then a GIS-based buffer approach is applied to identify all the faults near the NPP, possibly influenced by the crustal deformation induced by the major seismogenic structures. Faults inside these areas have to be tested for “capability” according to the same time window defined for the primary seismogenic structures. If fault capability is confirmed or, eventually, cannot be assessed, the next step is to implement an approach based on the potential to affect the safety of the NPP site in terms of fault geometry, and potential displacement. Finally, in the case where the fault can affect the safety of the site, the third step is the PFDHA or, in other words, the calculation of the annual probability of exceedance of the potential co-seismic fault displacement; this displacement is to be compared with the fault displacement threshold that will impact the safety of the NPP site. We also consider the effect of site vicinity tectonism on site vibratory ground motion and discuss an example in the light of the use of the GMPE.

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.

We performed a review of a representative data set on coseismic surface deformation, derived from both interferometric synthetic aperture radar imaging and from a traditional field survey of surface faulting. This analysis indicates a minimum threshold value of Mw5.4–5.5 for earthquake-induced ground deformation and faulting, with an inherently lower limit of detection that makes it hard to recognize surface deformation caused by Mw< 4.5–5.0 events. Significant exceptions are represented by shallow (i.e., less than circa 5 km) events that occur in volcano-tectonic settings, where surface deformation and dislocation are also clearly detectable for Mwcirca 4.0. Furthermore, a statistically significant regression between the areal extent of surface deformation and maximum slip at surface is proposed. This correlation is discussed in relation to fault displacement hazard analysis for nuclear power plants. In particular, the deformation area is used to find a potential solution for the second and third criterion for defining a capable fault.

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 review of all available contemporary documents, i.e., technical and photographic reports, newspapers, and other archive material, of the 1908, M 7.1, Messina–Reggio Calabria earthquake has allowed to recognize and classify a large number (365) of independent environmental effects of the earthquake and the subsequent tsunami. The effects have been categorized as slope movement, ground settlement, ground vertical movement and coastal retreat, liquefaction, ground crack, hydrological anomaly, gas emission, light, and rumble. No undisputable evidence of surface faulting has been pointed out. Nevertheless, the widespread and rather homogeneous subsidence of the coastal area of Messina (40–70 cm) might have been caused by slip along a NNE–SSW-trending, east-dipping fault, corresponding to the here proposed Messina Lineament. Likewise, slips along the Reggio Calabria, Armo and Motta San Giovanni faults, suggested by coastal subsidence and slides, ground cracks, and leveling data, cannot be ruled out. A large part of the achieved information has allowed to evaluate the epicentral intensity and local intensities at 74 sites, by applying the environmental seismic intensity scale ESI 2007. This study has led to the most comprehensive picture of the distribution and characteristics of coseismic environmental effects of that earthquake, a crucial knowledge to better estimate the future impact of a similar earthquake on a region that has seen a broad, and often poorly concerned, urban and infrastructural development since then.

Prediction of location and amount of slip for distributed faulting associated to strong earthquakes is a recently explored issue with major implications in terms of hazard assessment. Currently, the best practice involves the applications of Probabilistic Fault Displacement Hazard Analysis (PFDHA) whose results fit sufficiently well real data in the near-range of the primary fault but show considerable inaccuracies in the far-range. We believe that this inaccuracy descends from the biased earthquake databases used for regression analysis, whose data, relative to old earthquakes, were largely collected only by field surveys focused close to the primary fault (i.e., near-range). Remotely-sensed data (i.e., Interferometric Radar Imaging – InSAR) offer the opportunity to precisely measure the surface deformation induced by strong earthquakes and thus to explore its possible relation with distributed faulting. We analyze the L'Aquila earthquake case study (29th April, 2009, Mw 6.3) and explore the correlation between location and slip on distributed faulting and InSAR-derived deformation field. We find a significant correlation between occurrence of distributed faulting and profile curvature of the dislocation field, in spite of the distance from the primary fault. Moreover, distributed faults tend to occur within the area deformed by the earthquake, as imaged by InSAR data and whose extent is directly proportional to the earthquake magnitude (Mw), according to a dataset of 30 recent earthquakes. We then propose that these observations have to be incorporated into the present PFDHA practice as limit boundaries to possible scenarios of probabilistic analysis and that an integrated use of field-based and remotely data collection have to be implemented, following strong earthquakes.

We describe and interpret the well exposed soft-sediment deformations preserved in a Mid-Pleistocene proglacial sequence outcropping at Albese con Cassano, near Como (Southern Alps, N Italy). The observed deformations affect six distinct stratigraphic intervals within the same depositional sequence. The stratigraphy of this sequence, the geomorphic setting, and the careful geological mapping of the area clearly show that these deformations are not the result of glaciotectonics or cryoturbation, but are due to six separate events of synsedimentary liquefaction. In particular, the 3 basal deformed units include sand and gravel volcanoes that formed at the bottom of a proglacial lake. We examined several hypothesis of possible causative mechanism for the formation of these features. Taking into account all the information available on the local geology and sedimentary environment, it is possible to assess that the liquefaction features at Albese con Cassano had a coseismic origin. To our knowledge, this would be the first report of similar evidence of paleoseismicity in the Lombardia Southern Alps. Also, there is no record of historical liquefaction triggered by seismic events in an area of ca. 70 km of radius near Albese con Cassano, including the town of Como, the large metropolitan area of Milano and most of W Lombardia, that is one of the largest industrial districts in Europe. Therefore, the interpretation of the observed deformations can have critical impact for understanding the current seismicity level in the region, and mitigating the associated risk. In this paper we show that this interpretation is not a simple process. Liquefaction features must be treated with caution in order to derive suitable information for seismic hazard characterization, even if their coseismic origin has been definitely proved. It is necessary to understand the amount of seismic shaking (for instance, in terms of local macroseismic intensity) that can have produced that specific feature at that specific site, the location of the causative seismic event (epicenter and focal depth), and eventually its size (in terms of epicentral intensity and/or earthquake magnitude). In the case of Albese con Cassano, the implications in terms of seismic hazard of the observed possible earthquake paleoliquefactions can only be assessed through the definition of several scenarios, taking into account: a) different thresholds of shaking for triggering the described synsedimentary structures, and b) different seismotectonic frameworks related to the Mid-Pleistocene to Holocene evolution of the S Alps, including seismicity induced by isostatic glacial rebound. We conclude that it is worth checking these scenarios in the field with further paleoseismological research on other possible evidence of past earthquakes. There are no unequivocal sedimentological indicators of paleoseismicity, however, when carefully interpreted within the proper local seismotectonic context and compared with other earthquake-induced features, soft-sediment deformations can offer information of critical value for seismic hazard assessment.

Analysis of borehole data together with two centuries of documentation has allowed the assessment of subsidence evolution in the area of the Pontina Plain, where peats extend to up to 60 m in thickness. This paper discusses the two phenomena (self-weight consolidation and reclamation activities) which have led to ground subsidence of almost 6 m over a period of 200 years.

This paper presents a case study of the chromosomal complement of 16 miceMus musculus domesticus Linnaeus, 1758 from the region near one of the most recent disastrous earthquakes in Italy (named Umbria-Marche 1997), with the aim of examining chromosomal variability among the mice from the seismically active zones. For the present investigation, the sampling sites were chosen in the vicinity of some active faults, supposedly the main earthquake generators in the area. In the three localities, that lie approximately on the fault lines, mice with a reduced chromosomal number (2n = 36 to 39) were trapped. This reduction is due to the presence of three different Robertsonian metacentrics — Rb(9.14), Rb(10.12) and Rb(15.17) — in both the homozygous and heterozygous states. Mice trapped in four localities more distant from the fault zone only had the standard karyotype (2n = 40). These results increase the need to analyze in more detail the distribution of karyotypes in relation with active faults.

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 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.

Care must be taken to provide reliable antiseismic protection in earthquake-prone areas where the impact of a large earthquake in megacities with industrial facilities as well as in ordinary buildings is liable to cause massive loss of human life and to cripple the nation's economy. This protection needs to take into account not only vibratory ground motion but also permanent ground failure, and notably surface-faulting hazard, a fact tragically illustrated during the recent events of Turkey and Taiwan. The purpose of this contribution is to conduct a survey of our current state of knowledge concerning theoretical relationships between earthquake source parameters, such as moment magnitude (M, M w), surface wave magnitude ( M S), seismic moment ( M O), stress drop (Δσ), rupture length ( L ), and displacement on the fault ( D ). A relationship is proposed that links M S to L and Δσ: M S = 2 log L + 1.33 log Δσ + 1.66, using a simple rupture model. Earthquake data from all over the world for which the parameters of rupture length, fault width ( W ), fault displacement, and surface-wave magnitude are available have enabled stress drop values to be computed for each event using both geological observation (Δσ1) and the previously proposed equation (Δσ2). The results obtained tend to indicate that stress drop values increase versus fault width (depth) up to approximately 15 km (corresponding perhaps to the brittle-ductile boundary). This increase is more pronounced in the case of reverse faults than it is for those with strike-slip or normal mechanisms. An equation of the type Δσ = kW n has been used to fit the data, and preliminary values for k and n have been supplied for the three slip types. For depths in excess of 15 km the data do not display significant variation (Δσ < 100 bars). These results are in agreement with certain laboratory models of the continental lithosphere. Although more data, particularly in the large-magnitude range, are needed to ascertain whether it is the W or the L model that better describes earthquake scaling laws, stress drop does not appear to be fault-length dependent, thus being supportive of the L model. The risk of surface faulting is dependent on the dynamic environment of the fault, that is, the stress drop, the rupture length, and the fault width. Although statistics show that surface faulting appears in most instances at magnitudes of at least 6.1, data from certain regions indicate that seismicity at superficial depths is under certain conditions accompanied by significant surface faulting even for magnitudes as small as 5.5, suggesting a change in scaling law. The threshold magnitude for surface faulting is accordingly seen to depend on the rheology of materials in the fault area and on the stress environment. Manuscript received 31 May 2000.

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.

Paleoseismology, the study of past earthquakes based on their geological record in the stratigraphy and landscape, is a successful newly developing field of research. The application of fault trench studies in volcanic environments is one of the youngest branches of paleoseismology. In this paper, we present the results of the first exploratory trenches excavated at Mt. Etna in Sicily, the largest European volcano. Modern surface faulting at Etna is a very well known feature, which poses significant hazard to the local community, both in terms of ground displacement of essential lifelines and ground shacking from frequent damaging earthquakes. However, while the geomorphology and the seismicity of the active fault in the Etna region consistently show very high rates of tectonic activity, the Holocene cumulative throw and slip-rates, along with the nature (coseismic vs. creeping fault slip), dimension and timing of the displacement events, are still poorly constrained. For this purpose, we selected as a sample area the Moscarello fault, one of the most outstanding segment of the Timpe system of active normal faults in the volcano’s lower eastern flank. Displaced landforms and volcanic units at the Fondo Macchia basin, in the central sector of this fault, indicate some hundreds of meters of vertical offset in the last ca. 80 kyr, with a long-term slip-rate substantially higher than 1.5–2.0 mm/yr. According to the historical sources and instrumental observations, the Moscarello fault ruptured four times in the last 150 years during shallow (H M s =3.7 , earthquake. The excavated sections provided direct stratigraphic evidence for a vertical slip-rate of 1.4–2.7 mm/yr in the last ca. 6 kyr. This should be regarded as a minimum slip-rate for the central section of the fault. We explored a single scarp at a single site, while we know from recent historical observations that several parallel scarps may rupture coseismically at Fondo Macchia. Thus, the relevant deformation rate documented for the modern period might be likely extended back in the past to a time-span of some thousands of years at least. As expected, for such a volcanic environment, the activity rates of the Moscarello fault are also significantly higher than for the Apennines normal faults, typically showing slip-rates lower than 1 mm/yr. The agriculturally reworked trench hangingwall stratigraphy did not allow to recognize individual displacement events. Nevertheless, the sedimentary structures observed in the trench footwall strongly suggest that, as for the last 150–200 years of detailed historical record, fault behavior at Fondo Macchia is governed by coseismic surface displacement rather than fault creep. This research confirms that paleoseismology techniques can be effectively applied also in active volcanic environments, typically characterized by rheology and, consequently, seismicity and fault dynamics very different from those of other tectonic environments in which paleoseismology has been firstly developed and is today extensively applied.

(1998). EVIDENCE FOR SURFACE FAULTING DURING THE SEPTEMBER 26, 1997, COLFIORITO (CENTRAL ITALY) EARTHQUAKES. Journal of Earthquake Engineering: Vol. 2, No. 2, pp. 303-324.

When dealing with hazard, the concept of fault capability (the probability of significant surface displacement in the near future) is more useful than the generic and often misleading concept of fault activity. The example of the Pernicana fault, located in the north-eastern flank of the Mt. Etna volcano is used here to illustrate the damage which can be expected in an urbanised area from a capable fault, in this case characterized by 'aseismic’ creep along part of its length. Along this fault, buildings, roads and other essential lifelines are being affected by slow, left-lateral displacement. The Pernicana fault is only one of a set of structures in the area whose movement, either connected to seismicity or not, is producing severe damage. First identified at the end of the last century, this source of hazard is, nevertheless, still poorly considered by planners and technicians. In Italy fault creep is quite rare outside the Etna region, but fault capability associated with strong earthquakes is relatively frequent, based on historical and palaeoseismological data, and is a feature that should be taken into account for hazard reduction programs.

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. For coherent slides, the correlation of magnitude or ESI intensity versus distance is fairly good and consistent with global datasets. Instead, rock falls show a less evident correlation with distance. We stress here the usefulness of such relationships to define the expected scenario of earthquake-induced landslides. However, the data base needs to be improved and enlarged to allow more robust estimates. © Springer-Verlag Berlin Heidelberg 2013.

EARTHQUAKE ENVIRONMENTAL EFFECTS, INTENSITY AND SEISMIC HAZARD ASSESSMENT: THE EEE CATALOGUE (INQUA PROJECT #0418)

The September–October 1997 seismic sequence in the Umbria–Marche regions of Central Italy has been one of the best studied from the seismological, macroseismic and geological point of view. Numerous papers have been published in the period immediately after the seismic sequence, providing a significant database of effects triggered by the earthquake on natural environment. In the following years, further studies have provided additional pieces of evidence that allow to better relate the seismic sequence with its geological background. Moreover, recent developments in the characterization of coseismic environmental effects provide new horizons in seismic hazard assessment (SHA) procedures, which should take into account even long term geomorphological and geological features resulting from repeated characteristic earthquakes (concept of “seismic landscape”). This paper reviews the current state of knowledge on the 1997 Umbria–Marche seismic sequence, with particular regard to coseismic environmental effects (primary and secondary), that have been used for ESI seismic intensity assessment, in order to verify if i) they are consistent with geological, seismological and macroseismic data in the location and characterization of the seismogenic structure, and ii) if they fit the “seismic landscape” features that mark the epicentral area of Colfiorito.

Historical seismicity provides only a partial indication of the seismotectonic character (i.e. earthquake potential) of a given region. Even in Italy, where a relatively long historical record exists, available catalogues are generally unsatisfactory for this purpose. Fortunately, strong earthquakes often leave geological evidence, herein referred to as seismites, that are mainly related to surface faulting, folding or other deformation, and occasionally to secondary ground failures (e.g. landslides, liquefaction features, etc.). These features may be preserved and, therefore, palaeoseismological studies may detect and date them, thereby permitting extension of knowledge beyond the local historical threshold (up to 2000 years in the most fortunate cases). This paper provides a summary of criteria which may aid in the identification of areas suitable for palaeo-earthquake investigation. Historical seismicity and the presence of well developed tectonic geomorphic features are recognized as the most reliable criteria for identifying active faulting. However, lack of these characteristics cannot be considered conclusive evidence for lack of activity. Palaeoseismological techniques aim at identifying not only the obvious effects of surface faulting, such as offset of young geologic units, but also the more subtle tectonic or non-tectonic features, including liquefaction structures, gravity features and coseismic uplift and/or subsidence. Finally, we discuss some questions that pertain to palaeoseismicity evaluation techniques. Among these are the reliability of the Quaternary dating techniques, the evaluation of the seismic energy released (minimum magnitude) and principally, the unequivocal identification of a seismic origin for the considered geological structures.

The Late Glacial and Holocene geological and environmental evolution of the Como lacustrine–palustrine basin has been broadly reconstructed based on (a) the collection and analysis of more than 100 borehole stratigraphies, (b) the drilling of three new shallow boreholes and the analysis of a new geological section and (c) several in situ and laboratory analyses (mineralogical, organic and pollen content, 14C dating). The long-term, natural tendency of the ground surface to sink where the Como urban area has developed has been verified and assessed. This tendency has resulted clearly controlled by the compaction of young unconsolidated sediments accumulated at the hydrologically closed SW tip of Lake Como. The definition of a minimum age for the deglaciation of the basin and for a correlated stratigraphic marker allowed broad quantification of the average velocity of land subsidence during the last ca. 17 000 cal BP, with a gradient of values close to 2.5 mm/yr along the axial zone of the basin toward the present-day lake. Burial depth of archaeological remains, related to Roman Age, and levelling monitoring since 1928 are in agreement with this estimate. During 1950–1975, because of deep water withdrawal, the Como area was affected by a human-induced, accelerated subsidence, with velocity (10–20 mm/yr) one order of magnitude higher than the natural one. After a period of deceleration (between the end of the 1970s and the end of the 1990s), during which some benchmarks even reversed their trend, persistent scatterer interferometry (PSI) data provided by Tele-Rilevamento Europa (TRE) for the period 1992–2003, and levelling data obtained by APAT in 2004, show that during the last decade the subsidence rate has returned to its physiologic long-term trend.

This paper aims at substantiating the basic postulate of the recent Earthquake Environmental Effects (EEE) scale proposed by the International Union for Quaternary Research (INQUA), that primary and secondary environmental effects of earthquakes provide invaluable information on the earthquake size and intensity field, complementing but also independently testing the results of the traditional damage-based macroseismic scales. The EEE scale is applied to five disastrous earthquakes, which occurred in Southern Italy since the end of the XVII century. For each considered earthquake, the available macroseismic data have been reviewed and integrated through an updated interpretation of the original texts. The cataloguing and analysis of the seismically induced environmental effects has provided (a) a more detailed picture of the macroseismic fields, (b) the chance to test the scaling of the EEE scale with the MCS and MSK macroseismic scales, confirming its good fit with the MSK/MM, (c) I0 estimates based on EEE scale in good agreement with I0 assessments derived from MCS/MSK scales, (d) further constrains for the new version of the EEE scale, (e) useful data for seismic zonation. These results have confirmed once more the essential role of EEEs in the process of seismic hazard assessment and risk reduction.

The use of ground effects for the evaluation of earthquake intensity is described and discussed. The importance of such effects, and the problems that arise when they are not properly considered, are analysed in particular. The opinions of many experts in the field, regarding the uselessness of such data because of their great variability, are refuted.

On 9 September 1998, at 13:28 local time (11:28 UTC), a moderate earthquake of Mw = 5.6 struck the Southern Apennines at the northwest margin of the Pollino Massif (the highest mountain range of the region, reaching elevations above 2,000 m a.s.l.; Figures 1 and 2). The macroseismic epicenter is located about 3 km southeast of Lauria, with a maximum intensity of VIII on the MCS scale (or MM or MSK; see below for a correlation among macroseismic scales); thus we refer to this event as the Lauria earthquake. Historical towns—such as Lagonegro, Lauria, and Castelluccio—suffered significant damage, in particular that of Rivello, which is a remarkable local artistic site. Several ground effects followed the shock, and a rockfall on the road between Cersuta and Acquafredda (site 9a in Figure 3) claimed one life. A moderate magnitude event, the Lauria earthquake, together with the 5 May 1990 Potenza earthquake ( Ms = 5.4), was the largest earthquake in southern Italy since the destructive 23 November 1980 Irpinia earthquake (Alessio et al., 1995, cum bib.; Table 1 and Figure 2A). The day after the shock we initiated a reconnaissance survey of the epicentral area in order to record the geological and environmental changes induced by the earthquake. Among many other effects, we observed the rejuvenation of a bedrock fault scarp. In this paper we focus on this evidence of tectonic surface rupture because it has significant implications for the seismic hazard assessment both in (a) this sector of the Apennines and (b) other parts of the world. 1. This is the first modern observation of earthquake surface rupture in the apparently “aseismic” Pollino region. Figure 2 shows that according to the historical seismic catalogs only a few moderate to small local earthquakes (I ≤ VIII MCS) affected this area, in …

The Pollino Range is the southernmost segment of the Southern Apennines at the boundary with the Calabrian Arc. While several strong earthquakes (magnitude 6.5–7.0) have occurred in nearby regions, the Pollino area has no known historical record of seismic events of magnitude > 5. We carried out an aerial photograph interpretation and a field survey of the Pollino fault (the major Quaternary normal fault of the area) in order to characterize geologically the seismic potential of this structure. We dug two sets of trenches across fault scarps within the apecies of latest Pleistocene to Holocene alluvial fans at the Masseria Quercia Marina (MQM) and Grotta Carbone (GC) sites, in the central segment of the southern Pollino Range front. At both sites we identified two surface faulting events affecting the alluvial fan deposits and two overlying colluvial units of historical age. The penultimate event produced a vertical offset of 80–90 cm at GC and 50–60 cm at MQM; while the last event produced a vertical offset of 40–50 cm at GC and few centimeters of offset at MQM. Detailed geomorphological field observations suggest that the two historical earthquakes reactivated the entire length of the Masseria Marzano-Civita segment of the Pollino fault (rupture length about 18 km). For events in this range of rupture length and vertical displacement, comparison with surface faulting earthquakes in the Apennines (and abroad) indicates a magnitude of 6.5–7.0. Therefore, the maximum potential earthquake and the seismic hazard of the Pollino area are significantly larger than that suggested by the available historical seismic catalogue.

Earthquake hazard analyses in Italy are mainly based on historical seismic catalogs. However, the completeness of the Italian catalog, which spans more than 2000 years, progressivcly decreases going back in time. In the Fucino basin, historical research has not produced evidence of large earthquakes before the January 13, 1915, event (M s = 7.0 ; 33,000 people killed). This event generated surface faulting along at least two parallel Quaternary normal faults bounding the eastern side of the basin (the Celano-Gioia and Parasano-Cerchio faults), over an end-to-end length of about 23 km, with a downthrow of 30-90 cm toward southwest. To improve geological aspects of the seismic history of this area, we trenched onc of the coseismic scarps along the Celano-Gioia fault. At a trench site, near the village of San Benedetto de' Marsi, the fault traverses the area formerly covered by the Fucino Lake, drained for farming in 1875 A.D. The evidence collected in the trenchcs suggests at least two large events in historical times before 1915. Radiocarbon dates constrain the age of event B between the 6th and the 9th centuries A.D., possibly coinciding with the cvent felt in Rome in 801 A.D. [Molin arid Guidoboni, 1989]. Event A probably occurred after the 10th ccntury A.D. and almost certainly before the 1349 A.D. earthquake, because historical studies show (1) that event A was not produced during the earthquake sequence that occurred in central Italy in 1349 A.D. [Molin and Guidoboni, 1989] and (2) that the post-1349 seismic catalog can be regarded as complete for surface faulting earthquakes. Surface displacements determined for events A and B, compared to the 1915 surface faulting, indicate that M > 6.5 earthquakes were associated with each rupturc. These obscrvations suggest that the return period for large earthquakes in the Fucino basin is shorter than that indicated by the historical record alone. The Fucino example clearly shows that thc cxceptionally long historical record in Italy is still inadequate for a comprehcnsive seismic hazard characterization.