ALBERT

Beschreibung: Results of probabilistic seismic hazard assessment (PSHA), in terms of macroseismic intensity applied to the Mt. Etna region, are presented. PSHA has been performed using a numerical procedure based on the extensive use of local macroseismic information, as an alternative to the usual Cornell-McGuire methods. The large amount of intensity data available for this area - coming from the Italian intensity database DBMI04 for the regional earthquakes, and from the Etna catalogue for the ‘local’ events - has provided fairly exhaustive seismic site histories (i.e. the data set of macroseismic observations available for a given locality) to estimate the seismic hazard for 402 localities on the volcano. In order to improve the completeness of the site catalogue when historical information is missing, observed intensity data have been integrated with values calculated from epicentral information obtained by using an attenuation law specific for the Etna region. Using a probability distribution considering the completeness of the input database and the uncertainty of intensity data, the hazard in terms of maximum intensity (Iexp) characterised by a 10% probability of exceedance in an exposure time of 50 years, has been computed. The highest values ( Iexp = IX or X) are found in the south-eastern flank of Mt. Etna while the rest of the volcano is exposed to a lower hazard (Iexp = VIII). Despite the low energy (M≤4.8) compared with that of the large regional earthquakes affecting the area (6.6≤M≤7.4), the local events strongly influence the pattern of the hazard in the eastern sector of Mt. Etna, representing a significant, and sole, source of hazard when a shorter exposure time (e.g. 30 years) is considered.

Beschreibung: Published

Beschreibung: 77-91

Beschreibung: N/A or not JCR

Beschreibung: reserved

Beschreibung: In this paper we describe briefly the activity and evolution of four mud volcano fields located in eastern Sicily, around the Mt. Etna edifice. Three of them, called “Salinelle dei Cappuccini”, “Salinelle del Fiume” and “Salinelle del Vallone Salato” based on their location, occur on the southewestern flank of Etna, between the Paternò and Belpasso villages, and are presently active. The fourth one, today extinct, was active on the farest northeastern sector of Etna, along the Ionian Sea coastline. It was called “Salsa di Fondachello” after the name of the closest village. Geologic surveys and well drillings suggest that fluids uprise through pre-existing volcanic necks in the “Salinelle dei Cappuccini” and “Salinelle del Fiume”, while for the “Salinelle del Vallone Salato” an alternative pathway through a fault plane is also proposed. The morphologic evolution of the Etnean mud volcano fields depends mainly on the density of the emitted muds and secondarily on the preexisting ground topography. Chemical analyses revealed that the water coming out from the mud volcanoes originates from a deep aquifer confined in the carbonatic rocks of the Etna basement and that the most abundant escaping gas is CO2 of magmatic origin. The “Salsa di Fondachello” first activity is associated with the occurrence of the destructive Val di Noto earthquake, on January 11th, 1693. It was again active from 1795 to 1832. Its last activity, started in March 1847, came to an end with the collapse of the mud volcano. Today a weak methane emission is the only evidence of endogenous activity in this area.

Beschreibung: Published

Beschreibung: Paris Sorbonne Université, Paris

Beschreibung: open

Beschreibung: Volcanoes represent an important natural source of several trace elements to the atmosphere. For some species (e.g., As, Cd, Pb and Se) they may be the main natural source and thereby strongly influencing geochemical cycles from the local to the global scale. Mount Etna is one of the most actively degassing volcanoes in the world, and it is considered to be, on the long-term average, the major atmospheric point source of many environmental harmful compounds. Their emission occurs either through continuous passive degassing from open-conduit activity or through sporadic paroxysmal eruptive activity, in the form of gases, aerosols or particulate. To estimate the environmental impact of magma-derived trace metals and their depositions processes, rainwater and snow samples were collected at Mount Etna area. Five bulk collectors have been deployed at various altitudes on the upper flanks around the summit craters of the volcano; samples were collected every two week for a period of one year and analyzed for the main chemical-physical parameters (electric conductivity and pH) and for major and trace elements concentrations. Chemical analysis of rainwater clearly shows that the volcanic contribution is always prevailing in the sampling site closest to the summit crater (about 1.5 km). In the distal sites (5.5-10 km from the summit) and downwind of the summit craters, the volcanic contribution is also detectable but often overwhelmed by anthropogenic or other natural (seawater spray, geogenic dust) contributions. Volcanic contribution may derive from both dry and wet deposition of gases and aerosols from the volcanic plume, but sometimes also from leaching of freshly emitted volcanic ashes. In fact, in our background site (7.5 km in the upwind direction) volcanic contribution has been detected only following an ash deposition event. About 30 samples of fresh snow were collected in the upper part of the volcano, during the winters 2006 and 2007 to estimate deposition processes at high altitude during cold periods. Some of the samples were collected immediately after a major explosive event from the summit craters to understand the interaction between snow and fresh erupted ash. Sulphur, Chlorine and Fluorine, are the major elements that prevailingly characterize the volcanic contribution in atmospheric precipitation on Mount Etna, but high concentrations of many trace elements are also detected in the studied samples. In particular, bulk deposition samples display high concentration of Al, Fe, Ti, Cu, As, Rb, Pb, Tl, Cd, Cr, U and Ag, in the site most exposed to the volcanic emissions: median concentration values are about two orders of magnitude higher than those measured in our background site. Also in the snow samples the volcanic signature is clearly detectable and decreases with distance from the summit craters. Some of the analysed elements display very high enrichment values with respect to the average crust and, in the closest site to the summit craters, also deposition values higher than those measured in polluted urban or industrial sites.

Beschreibung: Published

Beschreibung: Vienna, Austria

Beschreibung: 4.5. Degassamento naturale

Beschreibung: open