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De Matteis R.,University of Sannio | Convertito V.,Istituto Nazionale di Geofisica Vulcanologia | Zollo A.,University of Naples Federico II
Seismological Research Letters | Year: 2016

The analysis of earthquake focal mechanisms provides information about the stress regime, fault geometry, and deformation processes acting in a given region. Generally, the techniques aimed at determining focal mechanism are designed to work in a specific magnitude range operating both in the time and frequency domain and using different data (e.g., P polarities, S-wave polarization, S/P-amplitude ratios, etc.). In this article, we present a new method, Bayesian inversion of spectral-level ratios and P-wave polarities (BISTROP), that can be applied to both small and moderate-to-large magnitude events. BISTROP uses a Bayesian approach to jointly invert the long-period spectral-level P/S ratios and the P polarities to infer the fault-plane solutions. We apply this method to analyze synthetic data as well as those generated by real earthquakes. We find that the obtained solutions for moderate earthquakes are comparable with those obtained using moment tensor inversion, and they are more constrained with respect to the solutions obtained using only P-polarity data for small earthquakes. Source

Chiarabba C.,Istituto Nazionale di Geofisica Vulcanologia | Chiodini G.,Istituto Nazionale di Geofisica Vulcanologia
Geology | Year: 2013

The Apennines belt of Italy undergoes a northeast-trending extension at a rate of a few millimeters per year that generates moderate to large normal-faulting earthquakes. In this paper, we show that seismicity, large earthquakes, strong gas emission, and belt topography all correlate with a broad, low Vp anomaly in the uppermost mantle. We propose that a thermal/fluid anomaly in the mantle, associated with sub-lithospheric mantle replacement after delamination of the Adria lithosphere, supports the topography of the belt and drives the extensional tectonics. The mantle anomaly is likely caused by deep fluids coming from the dehydration of the material subducted during the Europe-Adria collision and the delamination of Adria. Beneath the belt, CO2-rich fluids are accumulated and occasionally discharged during large normal faulting earthquakes. After the replacement of sub-lithospheric mantle, the temperature at the base of the crust increases causing crustal stretching, anatexis, and strong degassing. © 2013 Geological Society of America. Source

Chiarabba C.,Istituto Nazionale di Geofisica Vulcanologia | di Stefano R.,Istituto Nazionale di Geofisica Vulcanologia
Journal of the Virtual Explorer | Year: 2010

In this paper, we report on the velocity structure and seismicity of the northern-central Apennines. Recent seismological studies elucidate the crust and uppermost mantle structure in this peculiar and controversial portion of the central Mediterranean region. Quaternary extension develops on a main NW-trending seismic belt located along the Apennines range, at the boundary between the Adria and Tyrrhenian lithospheres, i.e. a complex setting in a more general framework of the Africa-Eurasia collision. This boundary is well defined at Moho depth by tomographic Pwave velocity models and receiver function analyses. The characteristics of the mantle vary between the Tyrrhenian and Adria domains, suggesting that the Tyrrhenian wedge is widely permeated by fluids due to the presence of subducted lithosphere at depth. The seismic belt is fragmented into adjacent and laterally offset segments, whose length is in the order of tens of kilometres. This feature is consistent with the occurrence of moderate and large (M>6.0) normal faulting earthquakes. We hypothesize that the fragmentation derives from the extreme complexity of the pre-existing structure, where subsequent tectonic inversions, from the Mesozoic Tethys extension to the Neogene compression and then to the presently active extension, created a puzzling scenario of faults in the crust. Deep fluids formerly released by the subduction process and broadly stocked in the mantle wedge up-raise in the crust favouring the re-activation of the pre-existing structures in the extending Apennines range. Source

Giaccio B.,CNR Institute of Environmental Geology and Geoengineering | Regattieri E.,CNR Institute of Environmental Geology and Geoengineering | Wagner B.,University of Cologne | Galli P.,CNR Institute of Environmental Geology and Geoengineering | And 12 more authors.
Scientific Drilling | Year: 2015

An 82m long sedimentary succession was retrieved from the Fucino Basin, the largest intermountain tectonic depression of the central Apennines. The basin hosts a succession of fine-grained lacustrine sediments (ca. 900 m-thick) possibly continuously spanning the last 2 Ma. A preliminary tephrostratigraphy study allows us to ascribe the drilled 82m long record to the last 180 ka. Multi-proxy geochemical analyses (XRF scanning, total organic/inorganic carbon, nitrogen and sulfur, oxygen isotopes) reveal noticeable variations, which are interpreted as paleohydrological and paleoenvironmental expressions related to classical glacial-interglacial cycles from the marine isotope stage (MIS) 6 to present day. In light of the preliminary results, the Fucino sedimentary succession is likely to provide a long, continuous, sensitive, and independently dated paleoclimatic archive of the central Mediterranean area. © Author(s) 2015. Source

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