seismic response of a deep continental basin including velocity inversion the sulmona intramontane basin central apennines italy

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Multiple Lines of Evidence for a Potentially Seismogenic Fault Along the Central-Apennine (Italy) Active Extensional Belt–An Unexpected Outcome of the MW6.5 Norcia 2016 Earthquake

The Apenninic chain, in central Italy, has been recently struck by the Norcia 2016 seismic sequence. Three mainshocks, in 2016, occurred on August 24 (MW6.0), October 26 (MW 5.9) and October 30 (MW6.5) along well-known late Quaternary active WSW-dipping normal faults. Coseismic fractures and hypocentral seismicity distribution are mostly associated with failure along the Mt Vettore-Mt Bove (VBF) fault. Nevertheless, following the October 26 shock, the aftershock spatial distribution suggests the activation of a source not previously mapped beyond the northern tip of the VBF system. In this area, a remarkable seismicity rate was observed also during 2017 and 2018, the most energetic event being the April 10, 2018 (MW4.6) normal fault earthquake. In this paper, we advance the hypothesis that the Norcia seismic sequence activated a previously unknown seismogenic source. We constrain its geometry and seismogenic behavior by exploiting: 1) morphometric analysis of high-resolution topographic data; 2) field geologic- and morphotectonic evidence within the context of long-term deformation constraints; 3) 3D seismological validation of fault activity, and 4) Coulomb stress transfer modeling. Our results support the existence of distributed and subtle deformation along normal fault segments related to an immature structure, the Pievebovigliana fault (PBF). The fault strikes in NNW-SSE direction, dips to SW and is in right-lateral en echelon setting with the VBF system. Its activation has been highlighted by most of the seismicity observed in the sector. The geometry and location are compatible with volumes of enhanced stress identified by Coulomb stress-transfer computations. Its reconstructed length (at least 13 km) is compatible with the occurrence of MW≥6.0 earthquakes in a sector heretofore characterized by low seismic activity. The evidence for PBF is a new observation associated with the Norcia 2016 seismic sequence and is consistent with the overall tectonic setting of the area. Its existence implies a northward extent of the intra-Apennine extensional domain and should be considered to address seismic hazard assessments in central Italy

Newly identified active faults in the Pollino seismic gap, southern Italy, and their seismotectonic significance

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Lithosphere tectonic context of the carbonatite-melilitite rocks of Italy

ABSTRACT. -The occurrence in Italy of Quaternary carbonatite-melilitite rocks, belonging to the Intra-mountain Ultra-alkaline Province (IUP), is considered in order to discuss a likely geodynamic environment for the Tyrrhenian-Apennine system. The IUP tectonic setting is described at the crustal and lithospheric scale and compared with the HK-series of the Roman eo-magmatic Province. It is concluded that a suitable mantle source for the IUP and HKS melts products (e.g. a radiogenic source with a phlogopite-bearing carbonate peridotite composition) does not need either the westward subduction of the Adriatic continental lithosphere or a mantle plume. The IUP and HKS geochemistry, as well as the deformation history of the Tyrrhenian-Apennine system, is explained in the frame of a substantially passive intra-continental rift context. The peculiar metasomatism and high radiogenic content of the HKS and IUP mantle source is attributed to fluids directly deriving from the lower mantle. RIASSUNTO.-L'inquadramento geodinamico del sistema Mar Tirreno-Appenini e stato riconsiderato alia luce della recente scoperta in Italia di una serie di rocce carbonatitico-melilititiche di eta quatemaria appartenenti alia Provincia Ultra-alcalina Intramontana (IUP). Il contesto tettonico di IUP, e delle contigue serie alte in potassio (HKS) della Provincia Comagmatica Romana (RCP), e stato esaminato sia alla scala crostale sia a quella litosferica. Le sorgenti dei magmi IUP e HKS sono rappresentate da una peridotite radiogenica a flogopite e carbonato. L'ipotesi di un arricchimento isotopico della sorgente per azione di fluidi *Corresponding author, E-mail: [email protected] provenienti da uno slab in subduzione e insufficiente, in quanto la posizione di alcuni centri (es. area del Vulture) non e compatibile con quella di un possibile piano di subduzione ovest immergente; inoltre, non e necessaria, in quanto valori isotopici di Sr e Nd, simili a quelli delle rocce italiane, sono stati riscontrati in altre aree geodinamiche in distensione o intra-continentali. Si puo escludere anche l'attivita di un plume astenosferico, poiche non si osservano i fenomeni tipici di questo tipo di ambiente (doming crostale, elevate temperature astenosferiche, attivita magmatica che predata quella tettonica, forti valori di assottigliamento litosferico contro bassi valori di estensione litosferica). La geochimica delle rocce IUP ed HKS e 1' evoluzione geodinamica del sistema Tirreno-Appennini puo essere, invece, ben inquadrata in un contesto di rift passivo intra continentrale, che ha determinato forti estensioni litosferiche con conseguente sollevamento di una astenosfera arricchita in fluidi metasomatici e radiogenici. Questi fluidi potrebbero essere direttamente risaliti dal boundary layer localizza to ad una profondita di circa 670 km, al limite tra mantello superiore ed inferiore

Frontiers in earth sciences: new ideas and interpretation

A one-day symposium on new and conventional ideas in plate tectonics and Mediterranean geodynamics was held in Rome on February 19, 2003 at the headquarters of INGV. There were two main reasons for such an initiative. The first was an invitation to Giancarlo Scalera from the «Gabriele D'Annunzio» University of Chieti to present his alternative ideas on global tectonics to final year students of the Regional Geology course. The second was a reciprocal invitation to Giusy Lavecchia and Francesco Stoppa to explain their criticisms of the application of subduction-related models to Italian geology and to present their data on the recently discovered intra-Apennines carbonatite occurrences. It was decided to dedicate an entire day to seminars, involving people with a more conventional approach to geodynamics, especially those involved with seismic tomography. In the last few years, high-resolution mantle tomographic models have been widely used to unravel the geometry of subduction zones. A turning point in the field, however, was a review paper written by Fukao et al. (Rev. Geophysics, 39, 291-323, 2001) showing that there was no clear evidence for slab subduction down to the core-mantle boundary, thus posing a major problem on the balance between the lithosphere subducted at consuming plate margins and the large amount of oceanic lithosphere accreted at diverging plate margins. This prompted the need to re-evaluate the nature of subduction and plate margin evolution. Accepting the theory of plate tectonics, many problems remain open, especially those regarding plate driving mechanisms and their possible link with the forces developed at the core-mantle boundary. Might these forces trigger pulsating tectonic and magmatic activity, with mantle upwellings and large-scale emission of CO2, capable of causing dramatic changes in the composition of the atmosphere and changes at the Earth's surface? Could these lead to major catastrophic changes in Earth history? During the one-day symposium, a stimulating discussion took place involving different interpretations of observations, especially those relating to the geodynamics of the Mediterranean region. Although the papers in this collection do not provide unique solutions, they do, however, provide new insights into some problems and in some cases suggest new interpretations. Many questions also arise about the relationships between the tectonics of the lithosphere and the deep mantle processes. May the denser portions of the inner parts of the Earth transform into shallower, lighter chemical phases, with a possible increase in the Earth's volume? May the asthenosphere above growing plume heads be capable of dragging the overlying lithosphere? May mantle plumes be wet rather than hot? Some papers consider gravitation to be a driving mechanism for the nucleation of contractional belts and others even doubt the compressional origin of orogens. Finally – as a link to fundamental physics – an original mechanism of energy conversion from gravitons to photons is proposed as a supply of energy for global tectonic processes. Obviously, because of an often diverse philosophical and scientific background, it is difficult for the ideas presented in this supplement to be shared by all readers and contributors. But we hope that these ideas will help to encourage critical evaluations of some commonly accepted concepts in modern plate tectonic theory. European geoscientists have available to them an exceptional natural laboratory – the Mediterranean and surrounding orogens – complete with all of its paradoxes and contradictions. In this natural laboratory, we hope that new evidence and new solutions to a variety of problems outside of the Mediterranean region will be found

Magmatectonic Zonation of Italy: A Tool to Understanding Mediterranean

The Cenozoic magmatic activity of Italy is characterized, from the Alps to the Aeolian Islands, by an abundance of SiO2-undersaturated potassic to ultra-potassic rock-types (leucite-phonolites, leucitites, kamafugites and lamproites). Rocks of sodic character, mainly sub-alkaline transitional and alkaline basaltic in composition plus some isolate

Testing the seismogenic sources of the January 11th 1693 Sicilian earthquake (Io X/XI): insights from macroseismic field simulations

In January 11th 1693 an earthquake, commonly reported as the largest Italian seismic event (Io = X/XI MCS and Mw 7.4 according to CPTI04 reference catalogue), occurred in eastern Sicily, causing more than 54.000 casualties and totally destruction in the areas embracing the nowadays provinces of Catania, Siracusa and Ragusa. The entire Sicily Ionian coast was hit by a tsunami, with waves up to 8 metres high. Several geological sources differing in location, attitude and kinematics have been proposed by different authors for this earthquake: the NNW-SSE Malta Escarpment normal fault located offshore the eastern coast of Sicily, the nearly N-S Scicli strike-slip fault located in the central Hyblean plateau, the WSW-ENE Scordia-Lentini graben in the northern Hyblean region, the NW-dipping Ionian subduction plane, and lastly the NNW-dipping Sicilian Basal Thrust across the central-eastern Sicily and the Ionian offshore. In this paper, we attempt to discriminate among the above sources by applying a forward modelling technique which, starting from given fault model parameters (strike, dip, length, width, hypocentral location and magnitude) and reproducing acceleration time history above 1 Hz (the range of frequencies correlated with building damage), calculates the data point intensities at the surface. The differences between the observed and calculated macroseismic intensities, expressed as L1 norm, are discussed in order to identify the better analytical solutions. The obtained results are strongly dependent from the equivalent magnitude (Mw) attributed to the 1693 event, which in the literature ranges from Mw 6.8 to 8.0. Almost all the analysed fault models fall to reproduce the highest intensity (X/XI MCS) data points of the Hyblean region, suggesting that this area might have undergone a cumulative damage effects due to an intense foreshock activity (January 9th 1693, Mw 6.2, and January 11th 1693, morning, Mw 4.3). The portion of the macroseismic field located north of the Gela-Catania thrust front is better reproduced by the Malta Escarpment solution (Mw 7.1) and subordinately by the Sicilian Basal Thrust and by the Scordia-Lentini graben source models. The Hyblean portion of the field is better reproduced by the Ionian Subduction Plane (Mw 8) and subordinately by the Scicli line (Mw 7.4 and 7.1) source models. The entire field is better reproduced by the Scicli line related sources (Mw 7.1 and 7.4). Regional scale geological and seismotectonic considerations may help to further discriminate among the various sources