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This paper focuses on the recent tectonic evolution of the Bay of Naples with the aim of exploring the connection between local tectonics and volcanism. We reprocessed the seismic reflection dataset acquired in the area in the late 1973. The new processing was highly successful in obtaining a decisive strong reduction of random noise, removal of coherent noise and reduction of spatial aliasing. Classical interpretative schemes and complex attributes of seismic traces were used to reconstruct fault kinematics and reflector patterns. The results show that the faults affecting the Bay of Naples exhibit prevailing NE structural strikes, with the exception of the Pozzuoli Caldera where NW patterns are also common. Many faults are subvertical and show seismic evidence of volcanic activity along them. A main alignment of conjugate NE–SW faults, named here as “Magnaghi–Sebeto line”, intersects several submarine volcanic banks and separates the bay into two sectors, characterized by important geological, geophysical and petrochemical differences. The structural configuration of the bay may reflect the occurrence of either oblique extension or a transfer zone of the NW–SE fault system, along which, in the Campanian–Lucanian Apennine chain, great vertical displacements occur. 相似文献
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Luciano Telesca Vincenzo LapennaFilippos Vallianatos 《Physics of the Earth and Planetary Interiors》2002,131(1):63-79
Much recent work has been focused on understanding the statistical properties of time-occurrence series of earthquakes. Investigating into the patterns of seismic sequences reveals evidence of scaling features in temporal behavior. This is shown in the clustering properties of seismicity of the western Corinth graben, Greece from 1983 to 2000. Power-law behavior has been found by means of Allan factor analysis and Fourier spectra for the earthquake sequence, with consistent values for the scaling exponents, that decrease with the threshold magnitude. The analysis of the temporal variation of the scaling exponent, performed with different threshold magnitudes, reveals an enhancing of the clusterization in correspondence to larger events. The multifractal analysis of the temporal distribution of the events has shown a decrease of the intermittent character with the threshold magnitude. 相似文献
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Fluid migration and origin of a mud volcano in the Northern Apennines (Italy): the role of deeply rooted normal faults 总被引:1,自引:0,他引:1
ABSTRACT In the foothills of the Northern Apennines mud volcanoes are locally aligned along active normal faults, which allow surface leakage of fluids derived from deep sources (>3–6 km). The chemical and isotopic analysis of the fluids of a mud volcano, coupled with the reconstruction of its geological setting, allowed an investigation of the processes of migration and fluid flow. The fault system associated with the Regnano mud volcano drains a deep Miocene reservoir (foredeep marine deposits), which supplies formation water and thermogenic methane that has migrated from underlying Mesozoic carbonates. The muds from the volcano contain late Eocene microfossils and are extruded only during paroxysmal events. They have a shallower origin (about 1 km) from the base of Tertiary marine deposits deposited upon the upper tectonic nappe of the chain (Ligurian unit). This case study suggests that normal faults are very effective in controlling surface emissions. 相似文献
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Mafic eclogites sampled from a restricted area in the Lanterman Range (Antarctica) retrogressed variably under amphibolite facies metamorphism. Assemblages range from well-preserved eclogite, with minor growth of Na-Ca amphibole, to strongly retrogressed ones with extensive development of Ca amphibole. 40Ar-39Ar furnace step-heating experiments on the different amphiboles yield results varying from plateau ages of ~498 Ma to a near-plateau age of ~490 Ma, and the greater the amphibolite retrogression, the younger the age. 40Ar-39Ar infrared laser-probe analyses on rock chips from a well-preserved eclogite and a slightly retrogressed one reveal the presence of an excess argon component. Whereas excess argon is invariably present in garnet and clinopyroxene developed under high-pressure metamorphism, it is heterogeneously distributed in amphibole on a millimetre scale. Results indicate that excess argon was incorporated during high-pressure metamorphism; this component was then lost during retrogression, while a change in composition of ambient argon to atmospheric argon occurred. New 40Ar-39Ar data and previously published Sm-Nd garnet and U-Pb rutile ages obtained from the same well-preserved eclogite sample suggest that the oldest Na-Ca amphibole age is reliable and not an artefact due to the incorporation of excess argon. The variably retrogressed eclogites are thought to derive from different parts of the enclosing metasedimentary rocks that were variably invaded by fluids during amphibolite facies metamorphism. Thus the circulation of fluids promoting (re)crystallisation, and not temperature, was the main process controlling the rate of argon transport in the studied eclogites. The different 40Ar-39Ar ages are interpreted to record diachronous amphibole growth at different crustal levels during exhumation. Data indicate that there was about a 10-Ma interval between the eclogite facies stage (at ̿.5 GPa) and the Ca amphibole-hydration forming reaction (at 0.3-0.5 GPa); this translates into an average exhumation rate of 3-4 km/Ma. 相似文献
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The debris flow (DF) and debris flood (DFD) activity in the Rebaixader catchment (Spanish Pyrenees) is analyzed in this study. The research is focused on how precipitation leads to the triggering of torrential floods and influences the sediment availability during the recharge period, in a supply-unlimited catchment. Two kinds of correlations are studied: (1) the correlation between the rainfall features (intensity and kinetic energy) and the DF/DFD triggering and (2) the correlation between the hyetograph and the DF/DFD volumes. The tested hypothesis was that a greater amount of rainfall during the recharge period would produce a greater DF/DFD volume. The period between two consecutive DF/DFD events is processed using a variable, the Erosion Index, originally developed for the Universal Soil Loss Equation. This analysis considered the rainfall time series and 22 DF/DFD events registered during the period 2009–2015. The results show that the precipitation of the recharge period does not seem to have a strong influence on the mobilized volumes. In many cases, a second DF/DFD event was triggered soon after the previous event, which highlighted the role of the first event in creating an unstable state of the catchment. Additionally, a threshold relationship between the kinetic energy of the rainfall event and the maximum rainfall intensity for a 30-min period seems to be a good criterion to discriminate between triggering and non-triggering rainfall events. The results show no clear trends with which to forecast the sediment volume from precipitation, weakening the role of rainfall characteristics in determining the return period of mobilized sediment volumes in catchments similar to the Rebaixader torrent. 相似文献
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