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41.
Simona Petrosino Paola Cusano Mario La Rocca Danilo Galluzzo Justo Orozco-Rojas Mauricio Bretón Jesus Ibáñez Edoardo Del Pezzo 《Bulletin of Volcanology》2011,73(7):887-898
This paper presents an analysis of seismicity associated with the volcanic activity of Volcàn de Colima (México) and recorded
in the period November 2005–April 2006 during a field survey by the Istituto Nazionale di Geofisica e Vulcanologia (INGV)–Osservatorio
Vesuviano, the Observatorio Vulcanologico de Colima of Colima University and the Instituto Andaluz de Geofisica, University
of Granada. Three different types of volcanic earthquakes have been identified on the basis of their spectral properties:
Type A (0.3–1 Hz), Type B (1–5 Hz) and Type C (3–4 Hz). Results of polarization analysis applied to Type A events show a predominance
of radial motion, indicating that the wavefield comprises compressional waves (P) and shear waves polarized in the vertical
plane (SV), while the signal always begins with a negative polarity. Type A, B and C earthquakes have been located using both
a flat layered model and a 3D model including topography. Hypocentre distributions indicate that the source of Type A signals
is very shallow and confined to a small volume lying about 1 km below the crater. In contrast, the source of Type B and C
events is significantly deeper, with most hypocentres located in a volume of about 1 km3 centred at 2.5–3 km depth. A cluster analysis based on the cross-correlation among the waveforms of different events recorded
at the same station was applied to Type A earthquakes. Only two clusters, which include only a small percentage of events
were found, indicating that earthquake families were uncommon during the period of our survey. 相似文献
42.
Carmela Freda Mario Gaeta Biagio Giaccio Fabrizio Marra Danilo M. Palladino Piergiorgio Scarlato Gianluca Sottili 《Bulletin of Volcanology》2011,73(3):241-256
Generally, the intensity and magnitude of explosive volcanic activity increase in parallel with SiO2 content. Pyroclastic-flow-forming eruptions in the Colli Albani ultrapotassic volcanic district (Italy) represent the most
striking exception on a global scale, with volumes on the order of tens of cubic kilometres and K-foiditic compositions (SiO2 even <42 wt.%). Here, we reconstruct the pre-eruptive scenario and event dynamics of the ~456 ka Pozzolane Rosse (PR) eruption,
the largest mafic explosive event of the Colli Albani district. In particular, we focus on the driving mechanisms for the
unusually explosive eruption of a low-viscosity, mafic magma. Geologic, petrographic and geochemical data with mass balance
calculations, supported by experimental data for Colli Albani magma compositions, provide evidence for significant ingestion
of carbonate wall rocks by the Pozzolane Rosse K-foiditic magma. Moreover, the scattered occurrence of cored bombs in Pozzolane
Rosse pyroclastic-flow deposits records carbonate entrainment even at the eruptive time scale, as also tested quantitatively
by thermal modelling of magma–carbonate interaction and carbonate assimilation experiments. We suggest that the addition of
free CO2 from decarbonation of country rocks was the major factor controlling magma explosivity. High CO2 activity in the volatile component, coupled with magma depressurisation, produced extensive leucite crystallisation at short
time scales, resulting in a dramatic increase in magma viscosity and volatile pressurisation, which was manifested a change
of eruptive dynamics from early effusion to the Pozzolane Rosse's highly explosive eruption climax. 相似文献
43.
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45.
3-D geomechanical rock mass characterization for the evaluation of rockslide susceptibility scenarios 总被引:1,自引:1,他引:0
G. Gigli W. Frodella F. Garfagnoli S. Morelli F. Mugnai F. Menna N. Casagli 《Landslides》2014,11(1):131-140
An integrated methodology based on traditional field and remote surveys such as terrestrial laser scanning and terrestrial infrared thermography is proposed, with the aim of defining susceptibility scenarios connected to rock slopes affected by instability processes. The proposed methodology was applied to a rock slope threatening a coastal panoramic roadway located in western Elba Island (Livorno district, central Italy). The final aim of the methodology was to obtain an accurate three-dimensional rock mass characterization in order to detect the potentially more hazardous rock mass portions, calculate their volume, and collect all the required geomechanical and geometrical parameters to perform a detailed stability analysis. The proposed approach proved to be an effective tool in the field of engineering geology and emergency management, when it is often urgently necessary to minimize survey time when operating in dangerous environments and gather all the required information as fast as possible. 相似文献
46.
Luca Salvati Vittorio Gargiulo Morelli Kostas Rontos Alberto Sabbi 《Urban geography》2013,34(3):376-394
This paper quantifies the extent of exurban development in Mediterranean Europe. The assessment was carried out by studying changes in the urban-to-rural population density gradient between the years 1950 and 2010. Three of the six urban regions in this study have experienced population growth and moderate urban concentration, while two regions appear to be shifting toward population decline and urban de-concentration after having experienced compact expansion. A phase of recent re-urbanization has been observed in one region. Altogether, these findings indicate a common path of urban expansion among representative Mediterranean regions between 1950 and 1980 while, in the following period, the cities experienced distinct development phases. From this study, we conclude that exurban development is mainly the product of a shift from compact and dense to semi-compact and intermediate-density settlements. [Key words: semi-dense urban growth, density-distance curve, Mediterranean Europe]. 相似文献
47.
A Crustal Model for the Eastern Alps Region and a New Moho Map in Southeastern Europe 总被引:1,自引:0,他引:1
In the last two decades, south-central Europe and the Eastern Alps have been widely explored by many seismic refraction experiments (e.g., CELEBRATION 2000, ALP 2002, SUDETES 2003). Although quite detailed images are available along linear profiles, a comprehensive, three-dimensional crustal model of the region is still missing. This limitation makes this region a weak spot in continental-wide comprehensive representations of crustal structure. To improve on this situation, we select and collect 37 published active-source seismic lines in this region. After geo-referencing each line, we sample them along vertical profiles—every 50?km or less along the line—and derive P-wave velocities in a stack of homogeneous layers (separated by discontinuities: depth of crystalline basement, top of lower crust, and Moho). We finally merge the information using geostatistical methods, and infer S-wave velocity and density using empirical scaling relations. We present here the resulting crustal model for a region encompassing the Eastern Alps, Dinarides, Pannonian basin, Western Carpathians and Bohemian Massif, covering the region within $45^{\circ}\text{--}51^{\circ}\hbox{N}$ and $11^{\circ} \text{--} 22^{\circ}\hbox{E}$ with a resolution of $0.2^{\circ} \times 0.2^{\circ}.$ We are also able to extend and update the map of Moho depth in a wider region within $35^{\circ}\text{--}51^{\circ}\hbox{N}$ and $12^{\circ}\text{--}45^{\circ}\hbox{E},$ gathering Moho values from the collected seismic lines, other published dataset and using the European plate reference EPcrust as a background. All the digitized profiles and the resulting model are available online. 相似文献
48.
49.
Alfredo Seritti David Pellegrini Elisabetta Morelli Corrado Barghigiani Romano Ferrara 《Marine Chemistry》1986,18(2-4)
Copper complexing capacity of cell exudates of Dunaliella salina in natural seawater culture medium was investigated in order to evaluate the influence of this organism on speciation of trace metals in seawater.Seawater samples were collected at 200 m and 2 miles off the coast and immediately filtered. Copper complexing capacity (CCCu) and stability constants (K′) of related cupric complexes were then measured. They were, respectively, 27.1 × 10−8 mol l−1 and 0.56 × 107 l mol−1 for the samples collected at 200 m and 12.8 × 10−8 mol l−1 and 6.10 × 107 l mol−1 for those collected 2 miles off the coast. A stock culture (20 ml, 106 cells ml−1) in log-phase was inoculated in 2 l of each sample of filtered natural seawater. The trend of cell influence was estimated on filtered culture medium by measuring CCCu and K′ after 1 h, 3 and 7 days. From the results it appears that CCCu increased with respect to time and this was related to the growth rate, indicating a certain relationship with cell metabolic activity.It can be concluded that a comparison between the culture referring to 200 m and 2 miles, respectively, shows that the former presents a CCCu two times higher than the latter while the K′ is ten times higher at 2 miles than that at 200 m. 相似文献
50.
The synthesis of phytochelatins (PC), intracellular metal-binding polypeptides characterized by a repeating sequence of gamma-glutamic acid- cysteine (gamma-Glu-Cys) pairs, has been studied in laboratory cultures of the marine diatom Phaeodactylum tricornutum exposed to Cd, Pb or Zn. Cd and Pb were able to induce PC of different degree of polymerization. The accumulation of the peptides follows a direct relationship with the metal exposure. No PC induction was observed in Zn-treated cultures, although the intracellular concentration of Zn increased during exposure. Both in short-term (7 h exposure, 10 microM Cd or Pb) and 3-day experiments (metal concentration less than 0.5 microM), the major fraction of total PC gamma-Glu-Cys subunits synthesized was polymerized as PC2 when cells were exposed to Pb, but as PC4 when cells were exposed to Cd. In short-term experiments about 50% of the gamma-Glu-Cys residues of the cellular pool of glutathione was quickly and almost quantitatively converted into PC. Recovery experiments, in which metal-stressed cells are suspended in a metal-free medium, showed a decrease of the PC pool and a concomitant increase of glutathione, suggesting a mechanism of degradation and release of metal-phytochelatin complexes. 相似文献