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71.
Agnes Mazot Dmitri Rouwet Yuri Taran Salvatore Inguaggiato Nick Varley 《Bulletin of Volcanology》2011,73(4):423-441
During 2007–2008, three CO2 flux surveys were performed on El Chichón volcanic lake, Chiapas, Mexico, with an additional survey in April 2008 covering
the entire crater floor (including the lake). The mean CO2 flux calculated by sequential Gaussian simulation from the lake was 1,190 (March 2007), 730 (December 2007) and 1,134 g m−2 day−1 (April 2008) with total emission rates of 164 ± 9.5 (March 2007), 59 ± 2.5 (December 2007) and 109 ± 6.6 t day−1 (April 2008). The mean CO2 flux estimated from the entire crater floor area was 1,102 g m−2 day−1 for April 2008 with a total emission rate of 144 ± 5.9 t day−1. Significant change in CO2 flux was not detected during the period of survey, and the mapping of the CO2 flux highlighted lineaments reflecting the main local and regional tectonic patterns. The 3He/4He ratio (as high as 8.1 R
A) for gases in the El Chichón crater is generally higher than those observed at the neighbouring Transmexican Volcanic Belt
and the Central American Volcanic Arc. The CO2/3He ratios for the high 3He/4He gases tend to have the MORB-like values (1.41 × 109), and the CO2/3He ratios for the lower 3He/4He gases fall within the range for the arc-type gases. The high 3He/4He ratios, the MORB-like CO2/3He ratios for the high 3He/4He gases and high proportion of MORB-CO2 (M = 25 ±15%) at El Chichón indicate a greater depth for the generation of magma when compared to typical arc volcanoes. 相似文献
72.
73.
Salvatore Inguaggiato Fabio Vita Dmitri Rouwet Nicole Bobrowski Sabina Morici Aldo Sollami 《Bulletin of Volcanology》2011,73(4):443-456
On 27 February 2007, a new eruption occurred on Stromboli which lasted until 2 April. It was characterized by effusive activity
on the Sciara del Fuoco and by a paroxysmal event (15 March). This crisis represented an opportunity for us to refine the
model that had been developed previously (2002–2003 eruption) and to improve our understanding of the relationship between
the magmatic dynamics of the volcano and the geochemical variations in the fluids. In particular, the evaluation of the dynamic
equilibrium between the volatiles (CO2 and SO2) released from the magma and the corresponding fluids discharged from the summit area allowed us to evaluate the level of
criticality of the volcanic activity. One of the major accomplishments of this study is a 4-year database of summit soil CO2 flux on the basis of which we define the thresholds (low–medium–high) for this parameter that are empirically based on the
natural volcanological evolution of Stromboli. The SO2 fluxes of the degassing plume and the CO2 fluxes emitted from the soil at Pizzo Sopra la Fossa are also presented. It is noteworthy that geochemical signals of volcanic
unrest have been clearly identified before, during and after the effusive activity. These signals were found almost simultaneously
in the degassing plume (SO2 flux) and in soil degassing (CO2 flux) at the summit, although the two degassing processes are shown to be clearly different. The interpretation of the results
will be useful for future volcanic surveillance at Stromboli. 相似文献
74.
Paola Monaco Filippo Santucci de Magistris Salvatore Grasso Silvano Marchetti Michele Maugeri Gianfranco Totani 《Bulletin of Earthquake Engineering》2011,9(1):231-261
This paper describes a case-history of liquefaction occurred near the village of Vittorito after the April 6, 2009 L’Aquila
earthquake (moment magnitude Mw = 6.3), approximately 45 km far from the epicentre. In the document, first, an estimation of the seismic motion in the area
has been made. Thereafter, the performed geotechnical investigation is described, followed by the application of some fast
assessment criteria for the occurrence of liquefaction, recently proposed by the new Italian Building Code. A careful assessment
of all the parameters involved in conventional Seed and Idriss (1971) liquefaction analyses is considered. The cyclic resistance ratio CRR is evaluated by cone penetration tests CPT and by in
situ seismic dilatometer tests SMDT; in the latter case CRR is evaluated by different empirical correlations with shear wave
velocity Vs and horizontal stress index KD. Analytical data confirmed the observed occurrence of the liquefaction in Vittorito, even if the acceleration field in the
area, produced by the L’Aquila earthquake, was very low. 相似文献
75.
Carlo Baroni Francesco Fasano Giovanna Giorgetti Maria Cristina Salvatore Cristiana Ribecai 《Global and Planetary Change》2008,60(3-4):457-470
The relationship between the Ricker Hills Tillite (RHT), which represents the northernmost outcrop of lithified continental glacial deposits in Victoria Land, is discussed with respect to the glacial landscape assemblage of the Ricker Hills, a nunatak at the internal border of the Transantarctic Mountains. A warm-based ice sheet deposited the tillite and induced syn- to post-depositional glacial deformation under wet conditions both of the tillite and of the bedrock. The thickness of the ice sheet on the nunatak is estimated to have been 600 m, at most. The area had been deeply eroded before deposition of the RHT as documented by the low elevation of tillite outcrops located in overdeepened depressions of the nunatak. Micropaleontological analysis evidences only the presence of Permian to Jurassic palynomorphs. X-ray diffraction and SEM–EDS analyses of clay minerals in the RHT indicate continental chemical weathering under wet conditions after the RHT deposition. As documented by clay mineral assemblage variation in CRP drillholes, the progressive cooling of the Antarctic continent allowed chemical weathering in “warm” conditions until the Late Oligocene period in southern Victoria Land, leading to a chronological constrain for RHT deposition. Conservatively estimating the sea level to have been between the tillite outcrops and the erosional trimline limiting horns in the Ricker Hills, at the time of RHT deposition, we suggest that the maximum uplift of the area would not have exceeded 900–1500 m since at least Late Oligocene. 相似文献
76.
Giovanni Spagnoli Pierpaolo Oreste Salvatore Grancuore 《Marine Georesources & Geotechnology》2013,31(6):739-745
AbstractThe estimation of excavation rates in specific geological and geotechnical conditions is one of the most delicate aspects for mining and geotechnical operations particularly offshore. Many models have been developed to study the effectiveness of a drilling tool in contact with the ground. In this article, the results of laboratory cutting tests on concrete specimens are shown. The comparison of the results of laboratory tests with different predictive models, helped to identify the most representative models. The models were then used to study in more detail, the effectiveness of the excavation tools through a parametric analysis. The research helped to define how to obtain rubrics, which can estimate the theoretical net cutting production of an excavation machine, when the power of its engines is known, or to evaluate, when the requested net cutting production is available, the power that the cutting machine must have. The findings were also applied to a sandstone previously investigated. The results are based on theoretical models and cannot be used on geomaterials with the same (or similar) geotechnical properties. 相似文献
77.
Francesca Zuccarello Salvatore L. Guglielmino Viviana Battiato Lidia Contarino Daniele Spadaro Pado Romano 《Acta Geophysica》2009,57(1):15-23
This work aims to describe some aspects relevant to the emergence of magnetic structures on the solar surface. Using high
resolution photospheric and chromospheric data, besides than EUV images acquired by space telescopes, the dynamics of rising
flux tubes is studied. It is shown that, for both long-lived and short-lived magnetic regions, the flux tubes are initially
characterized by a high rising velocity, which eventually decreases as the region develops. Other results concern the timeline
of the active regions appearance in the atmospheric layers and the asymmetries in plasma downflows between preceding and following
legs of the flux tubes. These results are briefly discussed in the light of most recent models. 相似文献
78.
Ilia Louban Nicole Bobrowski Dmitri Rouwet Salvatore Inguaggiato Ulrich Platt 《Bulletin of Volcanology》2009,71(7):753-765
The simultaneous quantitative determination of two-dimensional bromine monoxide (BrO) and sulphur dioxide (SO2) distributions in volcanic gas plumes is described. Measurements at the fumarolic field on the island Vulcano (autumn 2004)
and in the plume of Mt. Etna volcano (spring 2005) were carried out with an Imaging DOAS instrument. The SO2 fluxes of several fumaroles were estimated from two-dimensional distributions of SO2. Additionally, the first two-dimensional distributions of BrO within a volcanic plume were successfully retrieved. Slant
column densities of up to 2.6 × 1014 molecules per square centimetre were detected in the plume of Mt. Etna. The investigation of the BrO/SO2 ratio, calculated from the two-dimensional distributions of SO2 and BrO, shows an increase from the centre to the edge of the volcanic plume. These results have significance for the involvement
of ozone during BrO formation processes in volcanic emissions. 相似文献
79.
80.