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A brief excursus is presented on the projects funded by the Civil Protection of the Friuli Venezia Giulia Region aimed at reducing seismic risk. The projects have tackled different aspects of seismic risk reduction: the regional seismometric network can give information on earthquakes in real time, the seismic hazard and risk maps represent the guidelines on how to construct new buildings and where to retrofit existing ones with high priority, the survey on the school buildings in Friuli-Venezia Giulia provides indications on what to do to make them safe. [ABSTRACT FROM AUTHOR]

Although earthquake prediction remains an ultimate goal of seismology, up to now only a very few events have actually been forecasted, while for many of them wrong or doubtful predictions were given and even some misunderstandings were produced. After reporting a couple of examples on the subject, the paper focuses on an accurate revision of the seismological data of the 1976 seismic sequence in Friuli (northeastern Italy), as well as on the analysis of the space distribution of the earthquakes aiming at investigating if any clue of possible identification of the epicentre of the main aftershocks was possible at that time or should be possible today. The final consideration is that, even with a good (or good enough) seismic monitoring, there was no clear evidence of epicentre migration towards the future location of the major events. [ABSTRACT FROM AUTHOR]

The duration magnitudes in the North-Eastern Italy Seismic Network (OX) catalogue have been thoroughly revised. Historically, but also today for homogeneous continuity with the past, this catalogue, released yearly by the National Institute for Oceanography and Experimental Geophysics, provides local magnitudes in terms of duration magnitude (MD). Unfortunately, the earthquake total durations were calibrated on a local Richter magnitude (ML) data set characterized by a demonstrated small bias. In this work, based on a revised and corrected ML catalogue of the Trieste seismological station, computed in accordance with the original Wood Anderson requirements and validated in turn with the available moment magnitude estimates, new linear empirical regressions between ML and earthquake total duration have been performed, aimed at producing a homogeneous catalogue of locations and MD for the eastern Southern Alps. [ABSTRACT FROM AUTHOR]

Immediately after an earthquake, a rapid estimation of the seismic impact is crucial to carrying out a prompt and appropriate Civil Protection response. This is particularly important in districts characterized by frequent and moderate-to-high seismicity, as is the case in the north-eastern part of Italy. In this paper, the authors illustrate an innovative approach developed in the Friuli Venezia Giulia Region (in north-eastern Italy), based on the active contribution of Civil Protection volunteers. The methodology is based on the rapid and pre-codified communication of the earthquake effects, focusing on two main aspects: (i) the observed effects on people and buildings in the urban areas, and (ii) the structural and non-structural damage observed on pre-identified buildings. In particular, this paper illustrates the methodology and its integration into the seismic emergency plans of the municipalities in the Friuli Venezia Giulia Region and discusses the first test, which occurred during a full-scale exercise and on the occasion of recent minor earthquakes affecting the area. [ABSTRACT FROM AUTHOR]

The zonation presented in this study has been developed with the aim of applying it as a branch of the logic tree that will be used for the new Italian seismic hazard map, presently in preparation according to the approach of seismotectonic probabilism. With respect to the zonation used for the present official seismic hazard map of Italy, the zonation proposed here considers narrower sources and is based on new and updated seismological data. In particular, some new seismogenic zones are proposed here, introducing areas that were not considered seismogenic until now (e.g., the narrow sources characterised by the presence of transform faults which are almost normal to the trend of the northern Apennines). The preliminary seismic hazard estimates produced with this new zonation aim to identify possible problems that the zonation introduces in the seismicity characterization of the seismogenic zones. As the present seismic hazard assessment was computed by considering a different attenuation model with respect to the one applied for the previous national seismic hazard maps, a re-elaboration of the most recent map referring to Italy has been developed: the comparison of the two maps is a good indicator of the areas where additional seismological investigation is needed to support the zonation presented here. In particular, some zones are not adequately documented with regard to seismicity and a different computation of the seismicity rates is suggested. [ABSTRACT FROM AUTHOR]

Three hundred and seventy-five earthquakes recorded by the Trieste station in the eastern Alps in the early instrumental period, i.e., before the occurrence of the destructive event of May 6, 1976, have been located after painstaking gathering of seismograms and bulletins. Analysis of the statistical parameters of the locations, together with comparisons with other instrumental and macroseismic locations, have allowed us to assess the quality of the results obtained, taking into account the often limited nature of the data. Using a process of digitization and the study of seismograms, focal parameters, particularly the magnitude MW, have been recovered for three earthquakes of the 1950s and 1960s. [ABSTRACT FROM AUTHOR]

The seismic risk reduction of important community buildings and critical facilities is one of the most delicate problems that administrators are being asked to tackle. The ASSESS project, aimed at assessing the seismic risk of school buildings in the Friuli Venezia Giulia region (NE of Italy), is a prototypal study, developed on sound technical and scientific bases, and useful for defining decision-making tools for preventive purposes. In particular, the ASSESS methodology identifies the possible actions for improving seismic safety, it makes an economic evaluation of these actions, and, moreover, defines through specific indicators the intervention priorities for reducing the seismic risk of school buildings throughout the studied area. [ABSTRACT FROM AUTHOR]

Seismic hazard maps that account for site amplification (soil seismic hazard maps) are very useful because they represent the expected ground motion at the Earth's surface, but need much more information and elaboration than the usual rock hazard maps. The regional soil hazard map has been developed for the Friuli Venezia Giulia region, in northeastern Italy, by considering the most updated approach. In fact, the structure of the seismic hazard analysis presented here is based on the logic tree approach to achieve a robust statistical computation taking into account, in addition to the aleatory variability, also the epistemic uncertainties. The logic tree adopted for rock and soft soil conditions consists of 54 branches: three seismogenic zonations, representing various levels of our seismotectonic knowledge, three methods for the seismicity rate computation, three statistical approaches for the maximum magnitude estimation, and two PGA attenuation models of different spatial relevance (European and Italian). An additional regional attenuation model was considered only for stiff soil conditions, increasing the number of branches of the logic tree to 81. A consolidated expeditive procedure, widely adopted in the United States, has been used to compute the soil ground motion, properly modified on the basis of specific calibrations based on the local geological conditions and the results of geotechnical soundings. The final result of this study is represented by the map of the expected ground motion in the Friuli Venezia Giulia region, computed considering the different litho-stratigraphic and morphological conditions existing in the area. This map clearly shows the contribution given by the soft sediments along the Alpine valleys and by the steep formation of the moraine amphitheatre in central Friuli. A comparison of these new results with those obtained by applying the amplification factors provided by the most popular seismic codes points out that the actual ground shaking could be notably larger than that obtained by the application of the seismic codes, suggesting a possible future implementation in the regional building code, so far not taken into account. [ABSTRACT FROM AUTHOR]