Flare forecasting based on sunspot-groups characteristics     

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   

Cluster analysis of soil CO<Subscript>2</Subscript> data from Mt. Etna (Italy) reveals volcanic influences on temporal and spatial patterns of degassing     

Salvatore Giammanco  Pietro Bonfanti 《Bulletin of Volcanology》2009,71(2):201-218

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   

Chemical and isotopic compositions of thermal springs,fumaroles and bubbling gases at Tacaná Volcano (Mexico–Guatemala): implications for volcanic surveillance     

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 δ¹³C_CO2 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   

Thermal expansion-contraction and slope instability of a fumarole field inferred from geodetic measurements at Vulcano     

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   

Time-space variation of volcano-seismic events at La Fossa (Vulcano, Aeolian Islands, Italy): new insights into seismic sources in a hydrothermal system     

Salvatore Alparone  Andrea Cannata  Salvatore Gambino  Stefano Gresta  Vincenzo Milluzzo  Placido Montalto 《Bulletin of Volcanology》2010,72(7):803-816

We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of Vulcano (Aeolian Islands, Italy) during 2004-2006, and the dynamics of the hydrothermal system. During the period of study, three episodes of increasing numbers of volcano-seismic events took place at the same time as geothermal and geochemical anomalies were observed. These geothermal and geochemical anomalies have been interpreted as resulting from an increasing deep magmatic component of the hydrothermal fluids. Three classes of seismic events (long period, high frequency and monochromatic events), characterised by different spectral content and various similarity of the waveforms, have been recognised. These events, clustered mainly below La Fossa crater area at depths of 0.5–1.1 km b.s.l., were space-distributed according to the classes. Based on their features, we can infer that such events at Vulcano are related to two different source mechanisms: (1) fracturing processes of rocks and (2) resonance of cracks (or conduits) filled with hydrothermal fluid. In the light of these source mechanisms, the increase in the number of events, at the same time as geochemical and geothermal anomalies were observed, was interpreted as the result of an increasing magmatic component of the hydrothermal fluids, implying an increase of their flux. Indeed, such variation caused an increase of both the pore pressure within the rocks of the volcanic system and the amount of ascending fluids. Increased pore pressures gave rise to fracturing processes, while the increased fluid flux favoured resonance and vibration processes in cracks and conduits. Finally, a gradual temporal variation of the waveform of the hybrid events (one of the subclasses of long period events) was observed, likely caused by heating and drying of the hydrothermal system.  相似文献   

Determination of confined phreatic aquifer anisotropy     

Fallico C  Mazzuca R  Troisi S 《Ground water》2002,40(5):475-480

The determination of anisotropy in a phreatic aquifer by means of a pumping test can be carried out, under given conditions, with common analysis methods. This paper develops and applies an amended method based on a technique proposed by Boulton (1970). This new method enables a quick, simple determination of vertical hydraulic conductivity, given drawdown data from a pumping well and at least one observation well, that is applicable to confined phreatic aquifers.  相似文献   

Inorganic nitrogen control in wastewater treatment ponds from a fish farm (Orbetello, Italy): denitrification versus Ulva uptake   总被引：2，自引：0，他引：2  

Bartoli M  Nizzoli D  Naldi M  Vezzulli L  Porrello S  Lenzi M  Viaroli P 《Marine pollution bulletin》2005,50(11):1386-1397

The aim of this study was to quantify the N removal efficiency of an Ulva-based phytotreatment system receiving wastewaters from a land-based fish farm (Orbetello, Italy), to identify the main biogeochemical pathways involved and to provide basic guidelines for treatment implementation and management. Fluxes of O2 and nutrients in bare and in Ulva colonised sediments were assessed by light/dark core incubations; denitrification by the isotope pairing technique and Ulva growth by in situ incubation of macroalgal disks in cages. O2 and nutrient budgets were estimated as sum of individual processes and further verified by 24-h investigations of overall inlet and outlet loads. Ulva uptake (up to 7.8 mmol Nm(-2) h(-1)) represented a net sink for water column and regenerated NH4+ whilst N removal via denitrification (10-170 micromol Nm(-2) h(-1)) accounted for a small percentage of inorganic nitrogen load (<5%). Laboratory experiments demonstrated a high potential for denitrification (over 800 microM Nm(-2) h(-1)) indicating that N loss could be enhanced. The control of Ulva standing stocks by optimised harvesting of surplus biomass may represent an effective strategy to maximise DIN removal and could result in the assimilation of approximately 50% of produced inorganic nitrogen.  相似文献   

Continuous soil CO<Superscript>2</Superscript> and discrete plume SO<Subscript>2</Subscript> measurements at Mt. Etna (Italy) during 1997–2000: a contribution to volcano monitoring     

Benedetto?Badalamenti  Nicola?Bruno  Tommaso?Caltabiano  Fabio?Di Gangi  Salvatore?GiammancoEmail author  Giuseppe?Salerno 《Bulletin of Volcanology》2004,66(1):80-89

Continuous monitoring of soil CO₂ dynamic concentration (which is proportional to the CO₂ flux through the soil) was carried out at a peripheral site of Mt. Etna during the period November 1997–September 2000 using an automated station. The acquired data were compared with SO₂ flux from the summit craters measured two to three times a week during the same period. The high frequency of data acquisition with both methods allowed us to analyze in detail the time variations of both parameters. Anomalous high values of soil CO₂ dynamic concentration always preceded periods of increased flux of plume SO₂, and these in turn were followed by periods of summit eruptions. The variations were modeled in terms of gas efflux increase due to magma ascent to shallow depth and its consequent depressurization and degassing. This model is supported by data from other geophysical and volcanological parameters. The rates of increase both of soil CO₂ dynamic concentration and of plume SO₂ flux are interpreted to be positively correlated both to the velocity of magma ascent within the volcano and to lava effusion rate once magma is erupted at the surface. Low rates of the increase were recorded before the nine-month-long 1999 subterminal eruption. Higher rates of increase were observed before the violent summit eruption of September-November 1999, and the highest rates were observed during shorter and very frequent spike-like anomalies that preceded the sequence of short-lived but very violent summit eruptions that started in late January 2000 and continued until late June of the same year. Furthermore, the time interval between the peaks of CO₂ and SO₂ in a single sequence of gas anomalies is likely to be controlled by magma ascent velocity.Editorial responsibility: H. Shinohara  相似文献   

High-temperature rapid pyrometamorphism induced by a charcoal pit burning: The case of Ricetto,central Italy     

Flavio?CapitanioEmail author  Francesco?Larocca  Salvatore?Improta 《International Journal of Earth Sciences》2004,93(4):656-656

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A physical analogue model to analyse interactions between tensile stresses and dissolution in carbonate slopes     

Stefano Casini  Salvatore Martino  Marco Petitta  Alberto Prestininzi 《Hydrogeology Journal》2006,14(8):1387-1402

A physical analogue model was developed to analyse the relationship between tensional states in rock masses, seepage and karst processes. Use was made of an experimental apparatus consisting of two hydraulic circuits realized by drilling two holes into each of two blocks of sampled limestone from the central Apennines (Italy). A static load (208.85 kg) was applied to one of the blocks in order to elicit tensile stresses within it. Physical and chemical monitoring data showed that the main process involved was temperature-dependent CaCO₃ dissolution. This process was more marked in the loaded block circuit, as Ca⁺⁺ concentration in circulated water reached 54 mg/L, whereas only 28 mg/L was reached in the unloaded one. The interaction between load and dissolution caused the observed opening of microcracks, as confirmed by further increase of water loss and by dilution in the loaded block circuit, resulting in a decrease of Ca⁺⁺ concentration. These findings were confirmed by recording additional water losses after increasing the load up to 445.05 kg. A finite difference numerical model showed that tensile stresses (max 20 kPa) within the loaded block were clustered at the intersection of the main joints with the flowpaths, thus representing points of preferential and accelerated dissolution.This study is part of a research project on analogical and numerical modelling for geological risk mitigation being conducted at CERI, Research Centre for Geological Risks of the University of Rome “La Sapienza” (Valmontone, Roma, Italy; http://www.ceri@uniroma1.it).  相似文献