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181.
182.
Alessandro Bonaccorso Alessandro Bonforte Salvatore Gambino 《Bulletin of Volcanology》2010,72(7):791-801
Between 1987 and 1993, fumarole temperatures at the Fossa crater of Vulcano (Italy) were characterized by the highest values
since the 1920’s, increasing from about 300°C in 1987 to 690°C in May 1993, before decreasing to 400°C by 1996–1997. During
1990, Vulcano’s Electronic Distance Measurement (EDM) network was expanded to provide more detailed coverage of the northern
sector of the Fossa crater and, in particular, to monitor the movement of the northern flank the Fossa cone. Measurements,
carried out between 1990 and 1994, showed shortening by about 6 to 7 cm along baselines measured to a small section of the
northern rim. Over the following four years these baselines showed a slow extension by about 3 cm, to gradually recover part
of the previous deformation. We believe that the shortening and lengthening of the EDM baselines was respectively due to the
increasing and decreasing temperature of the rock body lying close to the deforming area. This caused thermal expansion, followed
by contraction. The positive movement of the rim was not completely matched by a negative recovery, suggesting that a non-recoverable
sliding movement was also responsible for some of the shortening of the baselines. We verified our hypothesis by calculating
the expected dilatation of a rock body, as a function of the volume of rock heated and its thermal expansion coefficient,
and compared the expected deformation to that observed. The geodetic investigation showed that the unstable portion affects
a small length of the rim (about 100 m long) and involves a volume of about 0.8 × 106 m3. However, this zone lies directly above a particularly unstable portion of the flank, as well as the main village and port
on the island. 相似文献
183.
Dmitri Rouwet Salvatore Inguaggiato Yuri Taran Nicholas Varley José A. Santiago S. 《Bulletin of Volcanology》2009,71(3):319-335
This study presents baseline data for future geochemical monitoring of the active Tacaná volcano–hydrothermal system (Mexico–Guatemala).
Seven groups of thermal springs, related to a NW/SE-oriented fault scarp cutting the summit area (4,100m a.s.l.), discharge
at the northwest foot of the volcano (1,500–2,000m a.s.l.); another one on the southern ends of Tacaná (La Calera). The near-neutral
(pH from 5.8 to 6.9) thermal (T from 25.7°C to 63.0°C) HCO3–SO4 waters are thought to have formed by the absorption of a H2S/SO2–CO2-enriched steam into a Cl-rich geothermal aquifer, afterwards mixed by Na/HCO3-enriched meteoric waters originating from the higher elevations of the volcano as stated by the isotopic composition (δD
and δ18O) of meteoric and spring waters. Boiling temperature fumaroles (89°C at ~3,600m a.s.l. NW of the summit), formed after the
May 1986 phreatic explosion, emit isotopically light vapour (δD and δ18O as low as −128 and −19.9‰, respectively) resulting from steam separation from the summit aquifer. Fumarolic as well as bubbling
gases at five springs are CO2-dominated. The δ13CCO2 for all gases show typical magmatic values of −3.6 ± 1.3‰ vs V-PDB. The large range in 3He/4He ratios for bubbling, dissolved and fumarolic gases [from 1.3 to 6.9 atmospheric 3He/4He ratio (R
A)] is ascribed to a different degree of near-surface boiling processes inside a heterogeneous aquifer at the contact between
the volcanic edifice and the crystalline basement (4He source). Tacaná volcano offers a unique opportunity to give insight into shallow hydrothermal and deep magmatic processes
affecting the CO2/3He ratio of gases: bubbling springs with lower gas/water ratios show higher 3He/4He ratios and consequently lower CO2/3He ratios (e.g. Zarco spring). Typical Central American CO2/3He and 3He/4He ratios are found for the fumarolic Agua Caliente and Zarco gases (3.1 ± 1.6 × 1010 and 6.0 ± 0.9 R
A, respectively). The L/S (5.9 ± 0.5) and (L + S)/M ratios (9.2 ± 0.7) for the same gases are almost identical to the ones calculated for gases in El Salvador, suggesting an
enhanced slab contribution as far as the northern extreme of the Central American Volcanic Arc, Tacaná. 相似文献
184.
Lidia Contarino Francesca Zuccarello Paolo Romano Daniele Spadaro Salvatore L. Guglielmino Viviana Battiato 《Acta Geophysica》2009,57(1):52-63
Our comprehension of solar flares is still lacking in many aspects and the possibility of observing active regions during
the first phases of flare occurrence is limited by our capability of doing accurate flare forecasting. In order to give a
contribution to this aspect, we focused our attention on the characteristics that must be fulfilled by sunspot-groups in order
to be flare-productive. We addressed this problem using a statistical approach: first, we analyzed sunspot-groups parameters
(i.e., Zürich class, magnetic configuration, area, morphology of the penumbra) and evolution; then, we performed a flare forecasting
campaign, based on the results obtained in the first phase and on real-time observations. The results obtained by comparing
the flare forecasting probability with the number of flares that have actually occurred are quite encouraging; we plan to
improve this procedure by including a bigger statistical sampling. 相似文献
185.
Giorgio Capasso Rocco Favara Salvatore Francofonte Salvatore Inguaggiato 《Journal of Volcanology and Geothermal Research》1999,88(3):209
Gas samples from some fumaroles at ‘La Fossa' crater and Baia di Levante on Vulcano Island and from a diffuse soil gas emission were analysed during 1995–1996, along with water samples from thermal wells in the area of Vulcano Porto. During 1996, we observed a significant increase both in the gas/steam ratio and in the CO2 concentration, as well as strong variations in δ13CCO2, δDH2O and δ18OH2O of fumarolic gases. These variations are probably related to an increased inflow of deep fluids of magmatic origin. The temperatures of fumaroles did not show remarkable variations except for fumarole F11. In this case, temperature increased by about 80°C from February to August 1996. During the same period, remarkable variations in temperature, phreatic level and chemical and isotopic composition of water were also recorded in one of the geothermal wells in the Vulcano Porto area (Camping Sicilia; T60°C). The observed variations in this well are probably related to a pressure build-up, occurring at least in the surficial part of the system, because of increased gas flux and/or decreased permeability of the fumarolic degassing system. Chemical and isotopic composition of the water showed that during this evolutionary phase, the content of fumarolic condensate in this well was about 80 to 90%. Based on the observation of physical and chemical variables of the Camping Sicilia fluids, during this phase of activity, it is concluded that this area is affected by a phreatic eruption hazard if a volcanic episode with high energy discharge in a limited time span occurs. It follows that this well may be considered as a preferential point for volcanic activity monitoring, both in the case of normal routine surveillance and in the case of inaccessibility to the crater area. 相似文献
186.
Application and validation of bivariate GIS-based landslide susceptibility assessment for the Vitravo river catchment (Calabria,south Italy) 总被引:2,自引:1,他引:2
Massimo Conforti Gaetano Robustelli Francesco Muto Salvatore Critelli 《Natural Hazards》2012,61(1):127-141
The Calabria (Southern Italy) region is characterized by many geological hazards among which landslides, due to the geological,
geomorphological, and climatic characteristics, constitute one of the major cause of significant and widespread damage. The
present work aims to exploit a bivariate statistics-based approach for drafting a landslide susceptibility map in a specific
scenario of the region (the Vitravo River catchment) to provide a useful and easy tool for future land planning. Landslides
have been detected through air-photo interpretation and field surveys, by identifying both the landslide detachment zones
(LDZ) and landslide bodies; a geospatial database of predisposing factors has been constructed using the ESRI ArcView 3.2
GIS. The landslide susceptibility has been assessed by computing the weighting values (Wi) for each class of the predisposing factors (lithology, proximity to fault and drainage line, land use, slope angle, aspect,
plan curvature), thus evaluating the distribution of the landslide detachment zones within each class. The extracted predisposing
factors maps have then been re-classified on the basis of the calculated weighting values (Wi) and by means of overlay processes. Finally, the landslide susceptibility map has been considered by five classes. It has
been determined that a high percentage (61%) of the study area is characterized by a high to very high degree of susceptibility;
clay and marly lithologies, and slope exceeding 20° in inclination would be much prone to landsliding. Furthermore, in order
to ascertain the proposed landslide susceptibility estimate, a validation procedure has been carried out, by splitting the
landslide detachment zones into two groups: a training and a validation set. By means of the training set, the susceptibility
map has first been produced; then, it has been compared with the validation set. As a result, a great majority of LDZ-validation
set (85%) would be located in highly and very highly susceptible areas. The predictive power of the model is considered reliable,
since more than 50% of the LDZ fall into 20% of the most susceptible areas. The reliability of the susceptibility map is also
suggested by computing the SCAI index, true positive and false positive rates; nevertheless, the most susceptible areas are
overestimated. As a whole, the results indicate that landslide susceptibility assessment based on a bivariate statistics-based
method in a GIS environment may be useful for land planning policy, especially when considering its cost/benefit ratio and
the need of using an easy tool. 相似文献
187.
Soil CO2 concentration data were collected periodically from July 2001 to June 2005 from sampling site grids in two areas located
on the lower flanks of Mt. Etna volcano (Paternò and Zafferana Etnea–Santa Venerina). Cluster analysis was performed on the
acquired data in order to identify possible groups of sites where soil degassing could be fed by different sources. In both
areas three clusters were recognised, whose average CO2 concentration values throughout the whole study period remained significantly different from one another. The clusters with
the lowest CO2 concentrations showed time-averaged values ranging from 980 to 1,170 ppm vol, whereas those with intermediate CO2 concentrations showed time-averaged values ranging from 1,400 to 2,320 ppm vol, and those with the highest concentrations
showed time-averaged values between 1,960 and 55,430 ppm vol. We attribute the lowest CO2 concentrations largely to a biogenic source of CO2. Conversely, the highest CO2 concentrations are attributed to a magmatic source, whereas the intermediate values are due to a variable mixing of the two
sources described above. The spatial distribution of the CO2 values related to the magmatic source define a clear direction of anomalous degassing in the Zafferana Etnea–Santa Venerina
area, which we attribute to the presence of a hidden fault, whereas in the Paternò area no such oriented anomalies were observed,
probably because of the lower permeability of local soil. Time-series analysis shows that most of the variations observed
in the soil CO2 data from both areas were related to changes in the volcanic activity of Mt. Etna. Seasonal influences were only observed
in the time patterns of the clusters characterised by low CO2 concentrations, and no significant interdependence was found between soil CO2 concentrations and meteorological parameters. The largest observed temporal anomalies are interpreted as release of CO2 from magma batches that migrated from deeper to shallower portions of Etna’s feeder system. The pattern of occurrence of
such episodes of anomalous gas release during the observation period was quite different between the two studied areas. This
pattern highlighted an evident change in the mechanism of magma transport and storage within the volcano’s feeder system after
June 2003, interpreted as magma accumulation into a shallow (<8 km depth) reservoir. 相似文献
188.
Angelo Ferro Salvatore Gambino Stefano Panepinto Giuseppe Falzone Giuseppe Laudani Bernard Ducarme 《Acta Geophysica》2011,59(3):618-632
In 2007–2008, we installed on Mt. Etna two deep tilt stations using high resolution, self-leveling instruments. These installations
are a result of accurate instrument tests, site selection, drilling and sensor positioning that has allowed detecting variations
related to the principal diurnal and semidiurnal tides for first time on Mt. Etna using tilt data. 相似文献
189.
Salvatore Manfreda Leonardo Mita Silvano Fortunato Dal Sasso Caterina Samela Leonardo Mancusi 《水文研究》2018,32(10):1420-1433
In hydrological modelling, the challenge is to identify an optimal strategy to exploit tools and available observations in order to enhance model reliability. The increasing availability of data promotes the use of new calibration techniques able to make use of additional information on river basins. In the present study, a lumped hydrological model—designed with the aim of utilizing remotely sensed data—is introduced and calibrated, adopting four different schemes that adopt, to varying extents, available physical information. The physically consistent conceptualization of the hydrological model used allowed development of a step by step calibration based on a combination of information, such as remotely sensed data describing snow cover, recession curves obtained from streamflow measurements, and time series of surface run‐off obtained with a baseflow mathematical filter applied to the streamflow time‐series. Results suggest that the use of physical information in the calibration procedure tends to increase model reliability with respect to approaches where the parameters are calibrated using an overall statistic based, considerably or exclusively, on streamflow data. 相似文献
190.