The Seismotectonic Significance of Geofluids in Italy

There is growing interest in how geofluid emissions are released in the atmosphere by the planet's geodynamic activity, and how much they contribute to the global budget of greenhouse gases. Many workers are addressing this issue with studies conducted at global scale, so as to get the required global-scale answers. The data available at the global scale on geofluids, faults, earthquakes and volcanoes, however, are generally too coarse to provide these answers. We investigate the relationships between geofluid emissions and tectonics at a more detailed scale. Building on over a century of data on geofluid emissions and on an extensive knowledge of the region's tectonics and seismicity, we focused on Italy, one of the areas of the globe that experience the largest release of natural CO2and CH4. We systematically overlaid and compared data collected by a number of workers into 13 published countrywide databases concerning geofluid emissions, carbon-bearing deposits, seismogenic faults, historical and instrumentally documented earthquakes, and heat flow observations. Our results indicate that 1) thermal springs and CO2emissions dominate in areas of mantle upwelling and crustal stretching, but also that 2) some of them occur in the extending inner Apennines, generally along major lithospheric chain-perpendicular lineaments that bound the largest normal faults. Conversely, 3) CH4emissions and mud volcanoes dominate in areas undergoing active contraction, where no CO2emissions are observed; in particular, we find 4) that mud volcanoes concentrate where the crests of active anticlines intersect major lithospheric chain-perpendicular lineaments. An overarching conclusion is that, in Italy, the release of geofluids is primarily controlled by deep crustal discontinuities that developed over the course of 5–10 My, and is only mildly affected by ongoing crustal strains. Geofluid emissions bring information on processes that occur primarily in the lower crust, marking the surface projection of generally hidden discontinuities that control the geometry and modes of seismic release. As such they may also provide valuable insight for improving the assessment of seismic hazard in hard-to-investigate seismically active regions, such as Italy

Database of Individual Seismogenic Sources (DISS), Version 3.2.1: A compilation of potential sources for earthquakes larger than M 5.5 in Italy and surrounding areas

Istituto Nazionale di Geofisica e VulcanologiaPublished2T. Deformazione crostale attiva3T. Sorgente sismica4T. Sismicità dell'Italia5T. Sismologia, geofisica e geologia per l'ingegneria sismica6T. Studi di pericolosità sismica e da maremoto4IT. Banche dat

Turning the rumor of the May 11, 2011, earthquake prediction in Rome, Italy, into an information day on earthquake hazard

A devastating earthquake was predicted to hit Rome on May 11, 2011. This prediction was never officially released, but it grew on the internet and was amplified by the media. It was erroneously ascribed to Raffaele Bendandi, an Italian self-taught natural scientist who studied planetary motions and related them to earthquakes. Indeed, around May 11, 2011, there was a planetary alignment, and this fed the credibility of the earthquake prediction. During the months preceding May 2011, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) was overwhelmed with requests for information about this prediction, by the inhabitants of Rome and by tourists. Given the echo of this earthquake prediction, on May 11, 2011, the INGV decided to organize an Open Day at its headquarters in Rome, to inform the public about Italian seismicity and earthquake physics. The Open Day was preceded by a press conference two days before, to talk with journalists about this prediction, and to present the Open Day. During this 'Day', 13 new videos were also posted on our YouTube/INGVterremoti channel to explain earthquake processes and hazards, and to provide periodic updates on seismicity in Italy from the seismicity monitoring room. On May 11, 2011, the INGV headquarters was peacefully invaded by over 3,000 visitors, from 10:00 am to 9:00 pm: families, students with and without teachers, civil protection groups, and many journalists. This initiative that was built up in a few weeks has had very large feedback, and was a great opportunity to talk with journalists and people about earthquake prediction, and more in general about the seismic risk in Italy

I sistemi informativi territoriali nella valutazione dell'erosione dei versanti: il caso del fiume Orcia

Dottorato di ricerca in scienze della terra. 12. ciclo. Docente guida Alessandro BiasiniConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

I caratteri della sismotettonica in Italia: osservazioni e modelli

Seismotectonics in Italy: data and modelsPublished139-1472T. Deformazione crostale attivaN/A or not JC

Physics-Based Simulation of Sequences with Foreshocks, Aftershocks and Multiple Main Shocks in Italy

We applied a new version of physics-based earthquake simulator upon a seismogenic model of the Italian seismicity derived from the latest version of the Database of Individual Seismogenic Sources (DISS). We elaborated appropriately for their use within the simulator all fault systems identified in the study area. We obtained synthetic catalogs spanning hundreds of thousands of years. The resulting synthetic seismic catalogs exhibit typical magnitude, space and time features that are comparable to those obtained by real observations. A typical aspect of the observed seismicity is the occurrence of earthquake sequences characterized by multiple main shocks of similar magnitude. Special attention was devoted to verifying whether the simulated catalogs include this notable aspect, by the use of an especially developed computer code. We found that the phenomenon of Coulomb stress transfer from causative to receiving source patches during an earthquake rupture has a critical role in the behavior of seismicity patterns in the simulated catalogs. We applied the simulator to the seismicity of the northern and central Apennines and compared the resulting synthetic catalog with the observed seismicity for the period 1650–2020. The result of this comparison supports the hypothesis that the occurrence of sequences containing multiple mainshocks is not just a casual circumstance

The seismicity of the Central Apennines (Italy) studied by means of a physics-based earthquake simulator

The application of a physics-based earthquake simulation algorithm to the Central Apennines, where the 2016-2017 seismic sequence occurred, allowed the compilation of a synthetic seismic catalog lasting 100 kyr, and containing more than 500,000 M ≥ 4.0 events, without limitations in terms of completeness, homogeneity and time duration. This simulator is based on an algorithm constrained by several faulting and source parameters. The seismogenic model upon which we applied the simulator code, was derived from the Database of Individual Seismogenic Sources including all the fault systems that are recognized in the Central Apennines. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which are comparable with the observations. These features include long-term periodicity and a realistic earthquake magnitude distribution. The statistical distribution of earthquakes with M ≥ 6.0 on single faults exhibits a fairly clear pseudo-periodic behavior, with a coefficient of variation Cv of the order of 0.4-0.8. We found in our synthetic catalog a clear trend of long-term acceleration of seismic activity preceding M ≥ 6.0 earthquakes and quiescence following those earthquakes. Lastly, as an example of a possible use of synthetic catalogs, an attenuation law was applied to all the events reported in the synthetic catalog for the production of maps showing the exceedance probability of given values of peak acceleration (PGA) in the investigated territory.Published916-9295T. Sismologia, geofisica e geologia per l'ingegneria sismica6T. Studi di pericolosità sismica e da maremotoJCR Journa

Lo scenario geologico dei terremoti in Pianura Padana e il grande disastro sismico del 3 gennaio 1117

Il 20 maggio 2012 un terremoto di magnitudo 5,9 ha colpito una vasta zona della Pianura Padana compresa tra le provincie di Modena, Ferrara e Mantova. Oltre a diversi centri storici, a numerose chiese e ad alcuni capannoni industriali il terremoto ha mandato in frantumi anche la diffusa convinzione che quella porzione del territorio padano, da sempre flagellata da alluvioni e dove appena 50 anni fa si è conclusa l’ultima di una serie di bonifiche, fosse almeno immune dal rischio dei terremoti. Negli anni successivi in molti si sono chiesti quale sia il reale livello della sismicità naturale della Pianura Padana, e uno dopo l’altro sono stati riscoperti terremoti antichi ma non per questo meno disastrosi come quelli che hanno distrutto Ferrara nel 1570, Argenta nel 1624, Cotignola nel 1688. Nel 2017, con il novecentesimo anniversario del terremoto del 1117, si sono accesi i riflettori anche sulla più disastrosa crisi sismica mai avvenuta nella Pianura Padana, innescando nuove analisi e riflessioni sul passato sismico dell’area più popolosa del nostro paese, e dunque anche sul futuro. Il livello non trascurabile della pericolosità sismica di alcune porzioni della Pianura Padana è stato chiaramente messo a fuoco dalle analisi della comunità scientifica già dal 2003, quando è stata pubblicata l’Ordinanza della Presidenza del Consiglio dei Ministri n. 3274, e successivamente dalla Mappa di Pericolosità Sismica elaborata dall’Istituto Nazionale di Geofisica e Vulcanologia (d’ora in avanti INGV) e nota come MPS04.1 La normativa sismica ancora oggi in vigore ha prontamente recepito le novità, ma una serie di ritardi e sostanziali sottovalutazioni del problema da parte degli amministratori hanno fatto in modo che il tema non entrasse nel dibattito pubblico almeno fino al maggio 2012. All’evoluzione delle conoscenze, e soprattutto della consapevolezza del problema sismico da parte dei cittadini e dei loro amministratori, è dedicata un’intera sezione del volume L’Italia dei disastri, curato da Emanuela Guidoboni e Gianluca Valensise e pubblicato nel 2013.2 Come ricercatori impegnati nella caratterizzazione sismica del territorio italiano3 da quasi due decenni abbiamo cercato di comprendere a cosa sia dovuta la scarsa percezione della sismicità di quell’ampia e importante porzione del nostro territorio nazionale che costituisce la Pianura Padana. A parte la relativa rarità dei forti terremoti, quantomeno negli ultimi tre secoli, va sicuramente considerato anche un diffuso approccio – più romantico che naturalistico – che tende a vedere nelle blande variazioni topografiche di quei territori la prova che il contesto geologico e geodinamico locale sia altrettanto ‘tranquillo’. Ma come dimostrano i terremoti che sono stati appena ricordati, questo punto di vista è del tutto sbagliato. Il paesaggio geologico sepolto della Pianura Padana è in effetti molto articolato e complesso, ed è sede di processi geodinamici certamente attivi; possiamo immaginarlo costituito da vere e proprie montagne ammantate da grandi quantità di sedimenti di origine marina e fluviale. Questi sedimenti hanno spessori molto variabili – da poco più di 100 metri a diverse migliaia di metri – e con la loro presenza obliterano le strutture tettoniche sottostanti. Queste possono in ogni caso essere rilevate e indagate quantomeno per via indiretta grazie alle numerose prospezioni geofisiche che sono state realizzate e rese disponibili dall’esplorazione petrolifera a partire dal secondo dopoguerra.Published31-481T. Struttura della Terra2T. Deformazione crostale attiva5T. Sismologia, geofisica e geologia per l'ingegneria sismica2TM. Divulgazione Scientific

A systematic analysis of directional site effects at stations of the Italian seismic network to test the role of local topography

Directional site effects observed at seismological stations on pronounced relief are analysed. We investigate the ground motion properties calculating horizontal-to-vertical spectral ratios and horizontal polarization of both ambient vibrations and earthquake records using broadband seismograms of the Italian seismic network. We find that a subset of 47 stations with pronounced relief results in a significant (>2) directional amplification of the horizontal component, with a well-defined, site-specific direction of motion. However, the horizontal spectral response of sites is not uniform, varying from an isolated (resonant) frequency peak to a broad-band amplification, interesting frequency bands as large as 1\u201310 Hz in many cases. Using 47 selected stations, we have tried to establish a relation between directional amplification and topography geometry in a 2-D vision, when applicable, through a morphological analysis of the digital elevation model using geographic information systems. The procedure computes the parameters that characterize the geometry of topographic irregularities (size and slope), in combination with a principal component analysis that automatically yields the orientation of the elongated ridges. In seeking a relation between directional amplification and the surface morphology, we have found that it is impossible to fit the variety of observations with a resonant topography model as well as to identify common features in the ground motion behaviour for stations with similar topography typologies. We conclude that, rather than the shape of the topography, local structural complexities and details of the near-surface structure must play a predominant role in controlling ground motion properties at sites with pronounced relie