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The design of critical facilities needs a targeted computation of the expected ground motion levels. The Trans Adriatic Pipeline (TAP) is the pipeline that transports natural gas from the Greek-Turkish border, through Greece and Albania, to Italy. We present here the probabilistic seismic hazard analysis (PSHA) that we performed for this facility, and the deaggregation of the results, aiming to identify the dominant seismic sources for a selected site along the Albanian coast, where one of the two main compressor stations is located. PSHA is based on an articulated logic tree of twenty branches, consisting of two models for source, seismicity, estimation of the maximum magnitude, and ground motion. The area with the highest hazard occurs along the Adriatic coast of Albania (PGA between 0.8 and 0.9 g on rock for a return period of 2475 years), while strong ground motions are also expected to the north of Thessaloniki, Kavala, in the southern Alexandroupolis area, as well as at the border between Greece and Turkey. The earthquakes contributing most to the hazard of the test site at high and low frequencies (1 and 5 Hz) and the corresponding design events for the TAP infrastructure have been identified as local quakes with MW 6.6 and 6.0, respectively.

In recent years, new approaches for developing earthquake rupture forecasts (ERFs) have been proposed to be used as an input for probabilistic seismic hazard assessment (PSHA). Zone- based approaches with seismicity rates derived from earthquake catalogs are commonly used in many countries as the standard for national seismic hazard models. In Italy, a single zone- based ERF is currently the basis for the official seismic hazard model. In this contribution, we present eleven new ERFs, including five zone-based, two smoothed seismicity-based, two fault- based, and two geodetic-based, used for a new PSH model in Italy. The ERFs were tested against observed seismicity and were subject to an elicitation procedure by a panel of PSHA experts to verify the scientific robustness and consistency of the forecasts with respect to the observations. Tests and elicitation were finalized to weight the ERFs. The results show a good response to the new inputs to observed seismicity in the last few centuries. The entire approach was a first attempt to build a community-based set of ERFs for an Italian PSHA model. The project involved a large number of seismic hazard practitioners, with their knowledge and experience, and the development of different models to capture and explore a large range of epistemic uncertainties in building ERFs, and represents an important step forward for the new national seismic hazard model.

In this study, we analyze the seismic signal generated by the 1963 Vajont catastrophic landslide recorded at the Worldwide Standardized Seismographic Station Network-Long Period station of Trieste (Italy). The landslide (nearly 260–270 million m3) invaded an artificial reservoir designed for electrical production, and generated a 220 m high wave that flowed over the dam and claimed the lives of approximately 2000 people. The original seismograms have been digitized and analyzed using time–frequency tools and numerical simulations. The results indicate that a seismic signal comparable to that generated by an Ms 3.7 earthquake was generated by the landslide. Furthermore, the calculated nearly 2×1014 J of frictional energy, considering the known parameter of the mass movement, is compatible with a friction coefficient of 0.29, in excellent agreement with the values from previous studies. The seismic efficiency that we calculate (1.12×10−4–4.45×10−4), also taking into account available data on the landslide, is within the range of values previously noted in literature. Finally, via the numerical simulations and adopting an ad hoc crustal model for the area, the origin time of the event is estimated at 21 hr 41 min 42 s UTC. The results confirm the importance of the re-analysis of analog seismograms with modern tools within a multihazard context.

In May 1976, a devastating earthquake of magnitude Ms 6.5 occurred in Friuli, Italy, resulting in 976 deaths, 2000 injured, and 60,000 homeless. It is notable that, at the time of the earthquake, only one station was installed in the affected region. The resulting lack of information, combined with a dearth of mitigation planning for responding to such events, lead to a clear picture of the impact of the disaster being available only after a few days. This region is now covered by nearly 100 seismological and strong-motion stations operating in real time. Furthermore, 30 average-cost strong-motion stations have been recently added, with the goals of improving the density of real-time ground-motion observations and measuring the level of shaking recorded at selected buildings. The final goal is to allow rapid impact estimations to be made to improve the response of civil protection authorities. Today, considering the higher density seismological network, new efforts in terms of the implementation and testing of earthquake early warning systems as a possible tool for mitigating seismic risk are certainly worthwhile. In this article, we show the results obtained by analyzing in playback and using an algorithm for decentralized onsite earthquake early warning, broadband synthetic strong-motion data calculated at 18 of the stations installed in the region, while considering the magnitude and location of the 1976 Friuli earthquake. The analysis shows that the anisotropy of the lead times is related not only to the finite nature of the source but also to the slip distribution. A reduction of 10% of injured persons appears to be possible if appropriate mitigating actions are employed, such as the development of efficient automatic procedures that improve the safety of strategic industrial facilities.

In the Kribi region (south-western Cameroon), a new industrial harbour has been built. This area is marked as a low-seismicity zone, according to the global seismic hazard map. This estimate is based, however, on a poorly documented data set. Industrial harbours are critical facilities and, consequently, appropriate cautions have to be taken in the seismic design. This paper illustrates the methodology adopted to compute the expected ground motion for the seismic design of the new harbour, starting from the available information. The standard probabilistic seismic hazard assessment is based on a logic tree approach considering areal and fault sources with two earthquake rate models (characteristic earthquake and Gutenberg–Richter), and two ground motion prediction equations. As expected, the obtained ground motion at the bedrock for a return period of 475 years is not very large [0.07 g, in terms of horizontal peak ground acceleration (PGA)] with a well marked peak between 0.1 and 0.2 s. This result is in agreement with that of the Global Seismic Hazard Assessment Project, where a general PGA between 0.04 and 0.08 g is associated with south-western Cameroon. The effects of local site conditions are evaluated through geophysical methods (single station and array surveys) and 1D linear-equivalent numerical modelling. Considering the two geotechnical models identified in the study region, by a specific geophysical survey executed during this study, local amplifications of 1.9 and 2.2 have been calculated for the two sectors, respectively. Furthermore, the results obtained, in terms of uniform hazard response spectra, have been used as guidelines to determine the design ground motions for the maritime and land infrastructures planned in the Kribi harbour area. This study represents a summary of the present knowledge on the seismicity of this part of Africa as well as the first regional and local seismic hazard assessment for the Kribi area.

In the last two decades, several studies addressed the revaluation and homogenization of the Italian instrumental seismic catalog, but all of them refer to the time interval from 1981, that is, the starting year of the Catalogo Strumentale dei Terremoti Italiani (CSTI). At the time, the CSTI was conceived as the continuation of the catalog of the Progetto Finalizzato Geodinamica (PFG) but, over time, the PFG catalog was almost totally forgotten, and presently it is even difficult to obtain because it is not provided by any website. In this work, we integrate a genuine copy of PFG, with additional locations from the bulletins of the Istituto Nazionale di Geofisica (ING, now known as INGV) and of the International Seismological Centre (ISC) and with local magnitudes from two couples of Wood–Anderson (WA) seismometers operational in Italy in the 1970s and 1980s, mostly derived from a careful scrutiny of paper bulletins of the Osservatorio Geofisico Sperimentale (OGS) and of the ING. We restrict our analysis to the time interval from 1960 to 1980 because, based on various evidence, we can infer that within such period most instrumental magnitudes reported by the PFG catalog are reasonably coherent with the Richter’s definition. Magnitudes provided by WA stations and other data sources are calibrated with respect to Mwby general orthogonal regressions. The final catalog from 1960 to 1980 contains 8536 earthquakes, of which we compute a true or proxy Mwmagnitude with related uncertainty for 6407. The analysis of the frequency–magnitude distribution indicates completeness for about Mw≥4:0. This work extends the time coverage of the Italian instrumental catalog to about 55 yrs before the present, allowing the statistical study of some important seismic periods that occurred, for example, in 1962 (Irpinia), 1968 (Belice Valley), 1976 (Friuli), 1979 (Umbria), and 1980 (Irpinia).

After a strong earthquake, the rapid identification of the extent of the affected area is the most crucial task of civil protection authorities. The information provided by those directly affected by an event makes the difference since it offers the opportunity to take advantage of direct observations and, in the case alert systems are available, to verify if they worked properly. Thanks to the fruitful collaboration between the Regional Civil Protection of Friuli Venezia Giulia and the National Institute of Oceanography and Applied Geophysics – OGS in Italy, a procedure for collecting rapid information about the impact of an earthquake using an expert crowdsourcing approach has been in place for some years. The volunteers of the civil protection, appropriately trained, upon receipt of the seismic event notification, are asked to rapidly compile a specific questionnaire, describing the impact of the event. Data are rapidly coded, and the results are summarized in a seismic impact map showing the effect of the earthquake throughout the territory in a simplified way. This map complements the impact estimation provided by the analysis of recorded shaking data. This paper describes the results obtained by analyzing the “Trained Volunteers Seismic Evaluation” questionnaire (TVSE) completed by volunteers for some of the most significant events in recent years.

Seismic hazard has been computed for the Northern Apennines in northern Italy based on a new seismogenic zonation. This zonation considers inclined (dipping) planes as seismogenic sources, defined on the basis of all the seismotectonic information available so far. Although these geometries are extremely rough because they simplify with a few inclined elements the totality of faults constituting a source, this model mimics the tectonic style better than that based on horizontal planes. Nevertheless, for a comparison between the new ground motions obtained and those available in the literature, the plane version of the zonation has been developed, where horizontal areas (the standard seismogenic zones), representing the surficial projection of the inclined planes, are used as seismogenic sources.

The seismic hazard assessment for Cuba and the surrounding regions has been performed according to the spatially smoothed seismicity approach. The major motivation for using this methodology is to avoid drawing seismic sources in a region where the seismogenic structures are not well known. We have defined two different seismicity models and three zonation models, based on the evidence of seismotectonic heterogeneity of the broader Cuban region, and two attenuation models for rock and three for soil. The resulting hazard estimates have been treated with a logic tree approach. The highest hazard was obtained around Santiago de Cuba with a PGA larger than 0.28 g on rock and 0.40 g on soil, for a 475-year return period. When the epistemic uncertainties of the different models considered are taken into account, these ground motion values exceed 0.40 g on rock and 0.60 g on soil. A comparison between these new hazard estimates and those computed according to the standard approach of the seismotectonic probabil...

A seismic hazard assessment for Cuba and the surrounding areas has been performed in response to a possible revision of the national building code. The hazard assessment has been done according to the standard methodology adopted by the Global Seismic Hazard Assessment Program and by introducing some computational techniques used for the seismic hazard map of Italy. Problems of earthquake catalog treatment, attenuation of peak ground acceleration and macroseismic intensity, as well as seismic source definition have been rigorously analyzed. Thirty-six seismogenic zones have been identified and characterized from a seismicity point of view. The present study offers a picture of the seismic hazard on Cuban territory based on historical seismicity and the benefits drawn from the most recent international investigations on the subject, such as the logic-tree approach used to represent the inevitable uncertainties encountered through the choice of attenuation relation. The final results are maps of the expected shaking with a 475-year return period in terms of peak ground acceleration and macroseismic intensity, which point out the high hazard along the southern coast of Cuba, where the expected ground motion, without the aleatoric uncertainty in the attenuation relations, is between 0.20 g and 0.30 g . The rest of the island is characterized by values representing less severe shaking.

Local soil conditions, roughlysummarised by considering a reference soil for eachmunicipality of the Friuli – Venezia Giulia region inNE Italy, are introduced into probabilistic seismichazard estimates: the subsequent improvement ischecked by comparing these new results and the maximumobserved intensities in each municipality toinvestigate if the major differences betweenprobabilistic estimates and actually observed data canbe explained by local site effects and/or by thegeometry of the seismogenic zones used in thecomputation. In addition, a comparison between the newprobabilistic hazard results, and the standard onesreferred to rock is made for the present and theproposed Italian seismic zonation. The resultsunderline the influence of the seismogenic model used,but are not determinant on the role of site effects.

Probabilistic seismic hazard maps, in terms of spectral acceleration and uniform hazard response spectra at given sites, considering local soil conditions, represent a much more complete estimate of the seismic hazard than the traditional maps in terms of peak ground acceleration or macroseismic intensity. This is particularly true when the requests of urban planners and engineers have to be met. The present analysis shows how some hazard parameters, such as the effective peak acceleration and the spectrum intensity, can well synthesise the overall information available from traditional probabilistic studies, but also suggests that soil condition is a first-order ingredient for effective seismic hazard mapping at national level. Three Italian towns, damaged by the 1997 Umbria–Marche earthquake sequence, are considered as example to demonstrate that: (1) soil condition dependent uniform hazard spectra well approximate actual spectra recorded during some events of the seismic sequence; (2) for these localities, the design spectrum of the present Italian seismic code does not seem adequate. These considerations have induced the Italian scientific community to propose an updating of the national seismic zonation on the basis of several hazard parameters, that are described in this paper.

A project has been implemented in recent years for assessing seismic hazard in the Italian territory on probabilistic bases, to be used as scientific background for the revision of the current seismic zonation. A consolidated approach was considered for the purpose; seismic hazard was estimated in terms of peak ground acceleration and macroseismic intensity. As the computer code employed allows the user to make specific choices on some input data, some rather unorthodox decisions were taken regarding earthquake catalogue completeness, seismicity rates, boundaries of the seismogenic zones, definition of the maximum magnitude, attenuation relation, etc. The overwhelming amount of geological and seismological data for Italy (just consider, for example, that the earthquake catalogue collects events which occurred over the last ten centuries) permits the operator to make different choices, more or less cautiously. It is quite interesting, then, to evaluate the influence of the specific choices on the final hazard results as a comparison to traditional possibilities. The tests performed clearly indicate the critical choices and quantify their contribution. In particular, we consider thorough comprehension of the space geometry of the earthquake source boundaries and the adequacy of the attenuation relation in modelling the radiation pattern very important.

The effects of the main earthquakes felt in Trieste are analyzed and compared. The most severe damage was caused by the events of 1511, whereas no information was found for the effects of the 1348 quake which should have been the strongest felt in the town. In fact, an earthquake in 1690 with a similar epicentre to that of 1348 but significantly weaker, caused some collapses. Uncertainties remain about the event of 1794, which was probably the only relevant local earthquake.

The region of the tectonic contact between the Alps and the Dinarides is studied comparing all the available geological, geophysical and seismological data. The peculiar crustal structures, in particular the difference in thickness of the Alps, Dinarides, and Pannonian basin can be correlated to the seismically active zones. The highest seismicity is related to the Adria microplate underthrusting the Southern Alps beneath the Friulian piedmont arc. This movement produces a composite lateral slip and an underthrust which is subparallel to the Dinarides along the Yugoslav coast. The seismicity in western Yugoslavia is more diffuse than in Friuli although it is possible to pick out three narrow parallel bands with dextral shear subparallel to the Periadriatic-Vardar fault system which separate the Apulia from the Pannonian area. The interaction of this system with the sinistral strike-slip faults of the western Carpathians belt enhances the seismicity of the easternmost sector of the Alps. Analogies and differences in the seismotectonic behaviour between central Friuli and western Yugoslavia are studied and a unique model with a vertical mechanical disengagement, at the rear of the compressive fronts of the Southern Alps and External Dinarides, is proposed.

The more significant geological and geophysical data available for northeastern Italy, between lake Garda and the Italian border with Yugoslavia, and between the Italian border with Austria and the river Po are analyzed and compared. From the geological point of view, a structural model showing sectors with different pre-Quaternary evolution, and a neotectonic model showing the tectonic evolution in the Middle Pleistocene-Holocene period, has been developed. The direction of the tectonic features is coherent with the present known stress field. The seismicity is concentrated in upper crustal levels (5-15 km) in Friuli but hypocentre depths of 25 km were recognized in the Garda area; it is due to the ongoing shortening between the Europe and Adria plates. A seismotectonic model is presented with four major structural units; these units are then further subdivided into ten homogeneous seismogenetic zones. -from Authors

The Italian "Gruppo Nazionale per la Difesa dai Terremoti" has conducted a project in recent years for assessing seismic hazard in the national territory to be used as a basis for the revision of the current seismic zonation. In this project the data on the major earthquakes were reassessed and a new earthquake data file prepared. Definition of a seismotectonic model for the whole territory, based on a structural-kinematic analysis of Italy and the surrounding regions, led to the definition of 80 seismogenic zones, for which the geological and seismic characteristics were determined. Horizontal PGA and macroseismic intensity were used as seismicity parameters in the application of the Cornell probabilistic approach. The main aspects of the seismic hazard assessment are here described and the results obtained are presented and discussed. The maps prepared show the various aspects of seismic hazard which need to be considered for a global view of the problem. In particular, those with a 475-year return period, in agreement with the specifications of the new seismic Eurocode EC8, can be considered basic products for a revision of the present national seismic zonation.