Short-Term Kinematics of the Adria Plate and Space-Time Distribution of Major Peri-Adriatic Earthquakes

Seismic activity is quite strong in the peri-Adriatic zones, whereas the internal part of the Adria plate is almost aseismic. This pattern suggests that Adria is a solid block that interacts with the surrounding belts, trying to move roughly northward. Each major earthquake in a peri-Adriatic zone triggers the acceleration of the decoupled Adria sector, which induces a perturbation of the stress/strain fields in the still blocked boundaries of the plate. Step by step, the displacement of Adria involves more and more northern zones to finally reach the northern front of the plate (eastern Southern Alps). This interpretation seems to be compatible with the time patterns of seismic activity in the main peri-Adriatic zones since 1600 A.D., which may suggest repeated northward migrations of seismic crises. Each supposed migrating sequence involves major earthquakes in most zones. The main features of the first 4 seismic sequences (1600-1930) are used to get insights into possible regularities in the progressive activations of the peri-Adriatic zones. This information and the main features of the ongoing migrating sequence (since 1931) are then used to tentatively recognize the peri-Adriatic zones where the occurrence of next major earthquakes may be most likely

Problems Associated With the Assessment of Local Site Effects Through a Multidisciplinary Integrated Study: The Case of Fivizzano’s Town (Italy)

The evaluation of local site effects, by means of ground response analyses, is a very complex and difficult task, which requires a multidisciplinary approach. This is operative philosophy expressed by VEL Project (Valutazione degli Effetti Locali), sponsored by Tuscany Region, to the aim to seismic risk characterization in the main seismic areas (i.e. Garfagnana, Lunigiana, Amiata, Valtiberina and Mugello). One of the most important urban centres, involved in the multidisciplinary activity of the VEL project, is certainly the town of Fivizzano located nearby the city of Massa, which was strongly damaged during the earthquake of September 1920 (the strongest seismic event occurred in Northern Apennines in the latest centuries). Remarkably good macroseismic information is available about the destructive impact yielded at Fivizzano by this earthquake (e.g. number of casualties, level of damage of buildings, etc). The main objective of this paper is to identify the occurrence of possible local site effects in the Fivizzano’s area following the 1920 earthquake and to quantify them by means of one and two-dimensional site response analysis. The input data required for study were obtained through a comprehensive geological survey and a multi disciplinary underground exploration of the area

Generation of Back-Arc Basins as Side Effect of Shortening Processes: Examples from the Central Mediterranean

7The evolution of the Mediterranean area since the Oligocene-Lower Miocene has been driven by the convergence of the surrounding plates. This implies that the observed deformation pattern in that region must be the most convenient shortening pattern, i.e. the one controlled by the minimum action principle. To understand why the fulfilment of such condition has required a complex spatio-temporal distribution of major tectonic events, such as uplift, lateral displacement and bending of orogenic belts, consumption of large lithospheric domains and formation of back arc basins, it may be very useful to take into account a basic tectonic concept, which helps to identify the process that can minimize the resistance of tectonic forces. Such concept starts from the fact that the most convenient consumption process is the one that involves low buoyancy oceanic lithosphere (Tethyan domains). However, such process is highly favoured where the oceanic lithosphere is stressed by vertical forces, a situation that develops when orogenic wedges are forced to over thrust and load the oceanic domain to be consumed. This interpretation can provide plausible and coherent explanations for the complex pattern of the observed deformations. In this view, the generation of back arc basins is taken as a side effect of an extrusion process, as suggested by numerical and mechanical experiments.reservedmixedMantovani E.; Viti M.; Babbucci D.; Tamburelli C.; Cenni N.; Baglione M.; D’Intinosante V.Mantovani, Enzo; Viti, Marcello; Babbucci, Daniele; Tamburelli, Caterina; Cenni, Nicola; Baglione, M.; D’Intinosante, V

Stima aggiornata della pericolosità sismica in Toscana e aree circostanti

Il confronto tra i danni che si sono verificati durante i terremoti del 2016 nell’Italia centrale e quelli previsti (con altissime probabilità) dalle carte di pericolosità attuali hanno chiaramente rivelato che gli interventi di prevenzione sismica effettuati in quelle zone sarebbero stati molto più efficaci se guidati dalle carte di intensità macrosismiche massime che erano state elaborate in base alle indagini svolte dal nostro gruppo di ricerca di Siena per le Regioni Marche e Umbria (Mantovani et alii, 2014a). Altre significative sottovalutazioni della pericolosità sismica, rispetto alle carte attualmente in vigore, erano state messe in evidenza dallo stesso gruppo di ricerca per la Regione Toscana (Mantovani et alii, 2012a) e per l’Emilia Romagna (Mantovani et alii, 2013), mediante indagini svolte in collaborazione con i responsabili di quelle due Regioni. In questa pubblicazione sono riportati alcuni importanti aggiornamenti delle informazioni precedentemente pubblicate, sia riguardo alle carte di pericolosità (riviste in base ai nuovi dati ora disponibili sui terremoti, Rovida et alii, 2016, e sui risentimenti osservati, Locati et alii, 2016), che alle nuove conoscenze acquisite sull’assetto sismotettonico dell’Appennino settentrionale. Per arricchire le considerazioni fatte sugli effetti dei terremoti del 2016, è anche riportato un contributo fornito dall’ ingegnere civile strutturista Danilo Fionga, che ha operato nelle zone interessate, in cui sono forniti alcuni interessanti suggerimenti per una corretta stima della pericolosità in zona sismica