Evoluzione dell'avanfossa messiniana dell'area laziale-abruzzese-marchigiana

La geologia del sedimentario nella ricerca di base e nelle sue applicazion

Maximum entropy estimation of values at Mt. Etna: comparison with conventional least squares and maximum likelihood results and correlation with volcanic activity

The variations of the b coefficient in the frequency-magnitude relationship for earthquakes which occurred at Mt. Etna from 01/01/90 to 31/12/92 are analyzed; the completeness threshold for our earthquakes catalogue is M = 2.30. The b values calculated using the Maximum Entropy Principle (MEP) are compared to those obtained by conventional methods of Least Squares (LS) and Maximum Likelihood (ML). All the differences among the b values computed using these methods, and the reasons for these differences, are discussed and examined. In particular, our results show that the b values obtained by MEP are lower than the others calculated using LS and ML; this implies that, on the average, LS and ML underestimate the seismic hazard at Mt. Etna. Moreover, temporal variations of bMEP are more evident than the corresponding ones of bLS and bML; indeed, in some cases the trend of bMEP variation is opposite those of bLS and bML. A significant correlation between temporal variations of the volcanic activity and the b values is evident only if the MEP is used; this means that, if b temporal variations are analyzed in order to detect changes in the volcano dynamics and predict the eruptions, the maximum entropy approach should be preferred. Finally, the observed pattern of bMEP temporal variations with regard to the changes in the volcanic activity is consistent with the hypothesis of a compressive stress field acting on Mt. Etna

The geodynamics of Mt. Etna volcano during and after the 1984 eruption

Data concerning M > 2.5 earthquakes that occurred at Mt. Etna volcano (Sicily, Italy) during the period April 15th - October 29th, 1984 are here presented and discussed. Only those events with reliable focal mechanisms (at least eight polarities) have been considered. Instrumental information comes from local seismic networks run by the University of Catania and the CNRS (Grenoble, France). The results obtained support the hypothesis that the seismicity and the volcanic activity at Mt. Etna are related to a complex stress field, due to the combined effects of the tectonics associated with the interaction between the African and Eurasian plates and the movement of magma into the crust. In particular, we hypothesize that the tectonic forces caused the end of the 1984 eruption, by means of a "locking mechanism"

Isochronal maps at Mt. Etna volcano (Italy): a simple and reliable tool for investigating large-scale heterogeneities

This paper analyses twelve etnean earthquakes which occurred at various depths and recorded at least by eleven stations. The seismic stations span a wide part of the volcanic edifice; therefore each set of direct P-wave arrival times at these stations can be considered appropriate for tracing isochronal curves. Using this simple methodology and the results obtained by previous studies the authors make a reconstruction of the geometry of the bodies inside the crust beneath Mt. Etna. These bodies are interpreted as a set of cooled magmatic masses, delimited by low-velocity discontinuities which can be considered, at present, the major feeding systems of the volcano

Maximum entropy estimation of values at Mt. Etna: comparison with conventional least squares and maximum likelihood results and correlation with volcanic activity

The variations of the b coefficient in the frequency-magnitude relationship for earthquakes which occurred at Mt. Etna from 01/01/90 to 31/12/92 are analyzed; the completeness threshold for our earthquakes catalogue is M = 2.30. The b values calculated using the Maximum Entropy Principle (MEP) are compared to those obtained by conventional methods of Least Squares (LS) and Maximum Likelihood (ML). All the differences among the b values computed using these methods, and the reasons for these differences, are discussed and examined. In particular, our results show that the b values obtained by MEP are lower than the others calculated using LS and ML; this implies that, on the average, LS and ML underestimate the seismic hazard at Mt. Etna. Moreover, temporal variations of bMEP are more evident than the corresponding ones of bLS and bML; indeed, in some cases the trend of bMEP variation is opposite those of bLS and bML. A significant correlation between temporal variations of the volcanic activity and the b values is evident only if the MEP is used; this means that, if b temporal variations are analyzed in order to detect changes in the volcano dynamics and predict the eruptions, the maximum entropy approach should be preferred. Finally, the observed pattern of bMEP temporal variations with regard to the changes in the volcanic activity is consistent with the hypothesis of a compressive stress field acting on Mt. Etna

Isochronal maps at Mt. Etna volcano (Italy): a simple and reliable tool for investigating large-scale heterogeneities

This paper analyses twelve etnean earthquakes which occurred at various depths and recorded at least by eleven stations. The seismic stations span a wide part of the volcanic edifice; therefore each set of direct P-wave arrival times at these stations can be considered appropriate for tracing isochronal curves. Using this simple methodology and the results obtained by previous studies the authors make a reconstruction of the geometry of the bodies inside the crust beneath Mt. Etna. These bodies are interpreted as a set of cooled magmatic masses, delimited by low-velocity discontinuities which can be considered, at present, the major feeding systems of the volcano

The geodynamics of Mt. Etna volcano during and after the 1984 eruption

Data concerning M > 2.5 earthquakes that occurred at Mt. Etna volcano (Sicily, Italy) during the period April 15th - October 29th, 1984 are here presented and discussed. Only those events with reliable focal mechanisms (at least eight polarities) have been considered. Instrumental information comes from local seismic networks run by the University of Catania and the CNRS (Grenoble, France). The results obtained support the hypothesis that the seismicity and the volcanic activity at Mt. Etna are related to a complex stress field, due to the combined effects of the tectonics associated with the interaction between the African and Eurasian plates and the movement of magma into the crust. In particular, we hypothesize that the tectonic forces caused the end of the 1984 eruption, by means of a "locking mechanism"

The Monterey event within the Central Mediterranean area. The shallow-water record

The middle Miocene is an important time to understand modern global climate evolution and its consequences on marine systems. The Mid-Miocene Climatic Optimum (MCO, between 17 and13.5 Ma), was the warmest time interval of the past 35 million years during which atmospheric CO2 concentrations were lower than today. In the MCO a significant carbon cycle perturbation occurred, expressed as a last long-term positive carbon isotope shift, known in literature as the Monterey Carbon Isotope Excursion and recorded in open-ocean settings. In this work, the lower to middle Miocene carbon isotope records from three different domains of the Central Mediterranean are analyzed with the aim of identifying the local carbonate platform response to the major global carbon cycle perturbation of the Monterey event. Carbon and Oxygen isotope ratios have been measured on samples belonging to three different stratigraphic sections, two of them representative of shallow water settings (Latium-Abruzzi and Apula Platforms), the latter of a hemipelagic setting (Umbria-Marche Basin). A well-defined Monterey Carbon Isotope Excursion is recorded also in these shallow-water sections. Despite their expected problematic stratigraphic constraints, a reliable age model is provided by calcareous nannofossil biostratigraphy and Strontium Isotope Stratigraphy. In both carbonate platform successions examined, the Monterey Carbon Isotope Excursion coincides with a spread of bryozoans over other carbonate-producing biota. The high productivity of the bryozoan dominated factory in the aphotic zone had an important control on the platform depositional profile. The high rates of sediment production in the deeper aphotic and oligophotic zones produced a depositional profile of a low-angle ram