ALBERT

Description: Operative seismic aftershock risk forecasting can be particularly useful for rapid decision-making in the presence of an ongoing sequence. In such a context, limit state first-excursion probabilities (risk) for the forecasting interval (a day) can represent the potential for progressive state of damage in a structure. This work lays out a performance-based framework for adaptive aftershock risk assessment in the immediate post-mainshock environment. A time-dependent structural performance variable is adopted in order to measure the cumulative damage in a structure. A set of event-dependent fragility curves as a function of the first-mode spectral acceleration for a prescribed limit state is calculated by employing back-to-back non- linear dynamic analyses. An epidemic-type aftershock sequence model is employed for estimating the spatio-temporal evolution of aftershocks. The event-dependent fragility curves for a given limit state are then integrated together with the probability distribution of aftershock spectral acceleration based on the epidemic-type aftershock sequence aftershock hazard. The daily probability of limit state first-excursion is finally calculated as a weighted combination of the sequence of limit state probabilities conditioned on the num- ber of aftershocks. As a numerical example, daily aftershock risk is calculated for the L’Aquila 2009 aftershock sequence (central Italy). A representative three-story reinforced concrete frame with infill panels, which has cyclic strength and stiffness degradation, is used in order to evaluate the progressive damage. It is observed that the proposed framework leads to a sound forecasting of limit state first-excursion in the structure for two limit states of significant damage and near collapse. Copyright © 2014 John Wiley & Sons, Ltd.

Description: Published

Description: 2179–2197

Description: 3T. Pericolosità sismica e contributo alla definizione del rischio

Description: JCR Journal

Description: reserved

Description: This article presents an integrated approach for the probabilistic systemic risk analysis of a road network considering spatial seismic hazard with correlation of ground motion intensities, vulnerability of the network components, and the effect of interactions within the network, as well as, between roadway components and built environment to the network functionality. The system performance is evaluated at the system level through a global connectivity performance indicator, which depends on both physical damages to its components and induced functionality losses due to interactions with other systems. An object-oriented modeling paradigm is used, where the complex problem of several interacting systems is decomposed in a number of interacting objects, accounting for intra- and interdependencies between and within systems. Each system is specified with its components, solving algorithms, performance indicators and interactions with other systems. The proposed approach is implemented for the analysis of the road network in the city of Thessaloniki (Greece) to demonstrate its applicability. In particular, the risk for the road network in the area is calculated, specifically focusing on the short-term impact of seismic events (just after the earthquake). The potential of road blockages due to collapses of adjacent buildings and overpass bridges is analyzed, trying to individuate possible criticalities related to specific components/subsystems. The application can be extended based on the proposed approach, to account for other interactions such as failure of pipelines beneath the road segments, collapse of adjacent electric poles, or malfunction of lighting and signaling systems due to damage in the electric power network.

Description: Published

Description: 524–540

Description: 3T. Pericolosità sismica e contributo alla definizione del rischio

Description: JCR Journal

Description: restricted

Description: For any scientist working in seismotectonics, the Calabrian Arc represents the most challenging area of Italy. Lying on top of a subduction zone, it is characterised by a complex geological structure largely inherited from the early stages of the collision between the Africa and Eurasia plates. The current and extremely vigorous seismogenic processes, although generated by a mechanism driven by the subduction, are no longer a direct consequence of plate convergence. About one fourth of the largest Italian earthquakes concentrates in a narrow strip of land (roughly 200x70 km) corresponding to the administrative region of Calabria. The present-day seismicity, both shallow and deep, provides little help in detecting the most insidious seismogenic structures, nor does the available record of GPS-detected strains. In addition to its fierce seismicity, the Calabrian Arc also experiences uplift at rates that are the largest in Italy, thus suggesting that active tectonic processes are faster here than elsewhere in the country. Calabrian earthquakes are strong yet inherently elusive, and even the largest of those that have occurred over the past two centuries do not appear to have caused unambiguous surface faulting. The identified active structures are not sufficient to explain in full the historical seismicity record, suggesting that some of the main seismogenic sources still lie unidentified, for instance in the offshore. As a result, the seismogenic processes of Calabria have been the object of a lively debate at least over the past three decades. In this work we propose to use the current geodynamic framework of the Calabrian Arc as a guidance to resolve the ambiguities that concern the identification of the presumed known seismogenic sources, and to identify those as yet totally unknown. Our proposed scheme is consistent with the location of the largest earthquakes, the recent evolution of the regions affected by seismogenic faulting, and the predictions of current evolutionary models of the crust overlying a W-dipping subduction zone.

Description: Published

Description: 365-388

Description: 4IT. Banche dati

Description: JCR Journal

Description: open

Description: Seismological, geological and geodetic data have been integrated to characterize the seismogenic structure of the late 2013-early 2014 moderate energy (maximum local magnitude MLmax = 4.9) seismic sequence that struck the interior of the Matese Massif, part of the Southern Apennines active extensional belt. The sequence, heralded by a ML = 2.7 foreshock, was characterized by two main shocks with ML = 4.9 and ML = 4.2, respectively, which occurred at a depth of ∼17–18 km. The sequence was confined in the 10–20 km depth range, significantly deeper than the 1997–1998 sequence which occurred few km away on the northeastern side of the massif above ∼15 km depth. The depth distribution of the 2013–14 sequence is almost continuous, albeit a deeper (16–19 km) and a shallower (11–15 km) group of events can be distinguished, the former including the main shocks and the foreshock. The epicentral distribution formed a ∼10 km long NNW–SSE trending alignment, which almost parallels the surface trace of late Pliocene–Quaternary southwest-dipping normal faults with a poor evidence of current geological and geodetic deformation. We built an upper crustal model profile for the eastern Matese massif through integration of geological data, oil exploration well logs and seismic tomographic images. Projection of hypocentres on the profile suggests that the seismogenic volume falls mostly within the crystalline crust and subordinately within the Mesozoic sedimentary cover of Apulia, the underthrust foreland of the Southern Apennines fold and thrust belt. Geological data and the regional macroseismic field of the sequence suggest that the southwest-dipping nodal plane of the main shocks represents the rupture surface that we refer to here as the Matese fault. The major lithological discontinuity between crystalline and sedimentary rocks of Apulia likely confined upward the rupture extent of the Matese fault. Repeated coseismic failure represented by the deeper group of events in the sequence, activated in a passive fashion the overlying ∼11–15 km deep section of the upper crustal normal faults. We consider the southwest-dipping Matese fault representative of a poorly known type of seismogenic structures in the Southern Apennines, where extensional seismogenesis and geodetic strain accumulation occur more frequently on NE-dipping, shallower-rooted faults. This is the case of the Boiano Basin fault located on the northern side of the massif, to which the 1997–1998 sequence is related. The close proximity of the two types of seismogenic faults at the Matese Massif is related to the complex crustal architecture generated by the Pliocene–early Pleistocene contractional and transpressional tectonics.

Description: Published

Description: 823-837

Description: 2T. Tettonica attiva

Description: JCR Journal

Description: partially_open

Description: The elevation of the Capo Vaticano coastal terraces (Tyrrhenian coast, central Calabria) is the result of a combination of regional uplift and repeated coseismic displacement. We subtract the regional uplift from the total uplift (maximum average uplift rates: 0.81–0.97 mm a)1 since c. 0.7 Ma) and obtain the residual fault-related displacement. Then, we model the residual displacement to provide constraints on the location and geometry of the seismogenic source of the 1905 M7 earthquake, the strongest – and still poorly understood – earthquake of the instrumental era in this area. We try four different potential sources for the dislocation modelling and find that (1) three sources are not compatible with the displacement observed along the terraces and (2) the only source consistent with the local deformation is the 100 - striking Coccorino Fault. We calculate average long-term vertical slip rates of 0.2–0.3 mm a)1 on the Coccorino Fault and estimate an average recurrence time of one millennium for a 1905-type earthquake.

Description: Published

Description: 378-389

Description: 2T. Tettonica attiva

Description: JCR Journal

Description: restricted

Description: Real-time seismology has made significant improvements in recent years, with source parameters now available within a few tens of minutes after an earthquake. It is likely that this time will be further reduced, in the near future, by means of increased efficiency in real-time transmission,increasingdatacoverageandimprovementofthemethodologies.Inthiscontext, together with the development of new ground motion predictive equations (GMPEs) that are abletoaccountforsourcecomplexity,thegenerationofstronggroundmotionshakingmapsin quasi-real time has become ever more feasible after the occurrence of a damaging earthquake. However, GMPEs may not reproduce reliably the ground motion in the near-source region where the finite fault parameters have a strong influence on the shaking. Inthispaperwetestwhetheraccountingforsource-relatedeffectsiseffectiveinbettercharacterizingthegroundmotion.WeintroduceamodificationoftheGMPEswithintheShakeMap softwarepackage,andsubsequentlytesttheaccuracyofthenewlygeneratedshakemapsinpredictingthegroundmotion.ThetestisconductedbycontrollingtheperformanceofShakeMap as we decrease the amount of the available information. We then update ShakeMap with the GMPE modified with a corrective factor accounting for source effects, in order to better constrain these effects that likely influence the level of (near-source) ground shaking. Weinvestigatetwowell-recordedearthquakesfromJapan(the2000Tottori, Mw 6.6,andthe 2008 Iwate-Miyagi, Mw7.0, events) where the instrumental coverage is as dense as needed to ensure an objective appraisal of the results. The results demonstrate that the corrected GMPE can capture only some aspects of the ground shaking in the near-source area, neglecting other multidimensional effects, such as propagation effects and local site amplification.

Description: Italian Presidenza del Consiglio dei Ministri, Dipartimento della Protezione Civile(DPC)under the contract 2007–2009 DPC-INGVS3project

Description: Published

Description: 1836-1848

Description: 3T. Pericolosità sismica e contributo alla definizione del rischio

Description: 4T. Fisica dei terremoti e scenari cosismici

Description: JCR Journal

Description: restricted

Description: Earthquakes caused by human engineering activities are commonly termed as “triggered” or “induced”. This class of earthquakes, though characterized by low-to-moderate magnitude, have significant social and economical implications since they occur close to the engineering activity responsible for triggering/inducing them and can be felt by the inhabitants living nearby, and may even produce damage. One of the first well-documented examples of induced seismicity was observed in 1932 in Algeria, when a shallow magnitude 3.0 earthquake occurred close to the Oued Fodda Dam (Gupta, 1985). By the continuous global improvement of seismic monitoring networks, numerous other examples of human-induced earthquakes have been identified (see Davies et al., 2013 for an overview). Induced earthquakes occur at shallow depths and are related to a number of human activities, such as fluid injection under high pressure (e.g. waste-water disposal in deep wells, hydrofracturing activities in enhanced geothermal systems and oil recovery, shale-gas fracking, natural and CO2 gas storage), hydrocarbon exploitation, groundwater extraction, deep underground mining, large water impoundments and underground nuclear tests (Davies et al., 2013). Despite the presence in the Sicilian territory of a large amount of engineering activities “potentially capable” of inducing seismicity, no extensive researches on this topic have been conducted to date. Hence, in order to improve our knowledge, and correctly assess the hazard at a specific location in the future, we started a preliminary study on the main engineering activities located on- and off-shore of Sicily (Southern Italy). To this end, in a first step we collected all the useful information coming from available on-line national and regional catalogues. The compiled database includes 46 dams, 598 quarries and 839 oil and gas wells for a total of 1483 engineering activities. Among these, 175 are located along the southern Sicilian coastal off-shore while the remaining 1308 are located inland. As a second step, we performed a detailed compilation of instrumental seismicity striking the investigated area. Continuous seismic monitoring of the whole Italian territory started in the 90s and is currently performed by the National Seismic Network managed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). In addition, monitoring and systematic analysis of seismic activity in eastern Sicily, by means of a dense local network, is performed also by the “Osservatorio Etneo” (INGV-OE), an INGV-branch located in Catania, close to Mt. Etna. Since 1983, earthquakes occurred in the entire Italian territory have been analysed and archived in the catalogue managed by the INGV headquarters in Rome (INGV-CNT; Castello et al., 2005; ISIDe Working Group - INGV, 2010), while since 1999, earthquakes occurred in eastern Sicily have been analysed and archived in the database of the INGV-OE (Alparone et al., 2009; Gruppo Analisi Dati Sismici, 2016). Because the INGV-OE catalogue covers with great details only the eastern sector of Sicily, while the INGV-CNT catalogues, extends back in time since 1983, in order to identify possible prospective effects of the human activities on the seismicity, here we took into account both catalogues. We considered only the seismicity occurred within the first 10 km of the crust because the induced seismicity should be likely confined in the shallower crust. As a final step, in order to identify prospective effects of the human activities on the seismicity, we investigated the spatio-temporal relationships between engineering activities and earthquakes, by adopting a statistic approach aimed to the detection of anomalous seismicity densities. Finally, we identified 46 engineering activities (2 dams, 16 wells and 28 quarries) characterized by anomalous seismicity density. These activities are mainly located in Western Sicily and on the eastern sector of the Hyblean Plateau, while a few number of activities are locate in northern Sicily and on the Island of Vulcano. Currently, we are performing detailed analyses on the nature of the observed seismicity activity in proximity of these engineering activities.

Description: Published

Description: Napoli (Italy)

Description: 6T. Sismicità indotta e caratterizzazione sismica dei sistemi naturali

Description: restricted