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http://hdl.handle.net/2122/2797
Authors: | Bianco, F.* Castellano, M.* Milano, G.* Vilardo, G.* Ferrucci, F.* Gresta, S.* |
Title: | The Seismic Crises at Mt. Vesuvius during 1995 and 1996 | Journal: | Physics and Chemistry of the Earth (A) | Series/Report no.: | 11-12 / 24 (1999) | Publisher: | Elsevier | Issue Date: | 1999 | Keywords: | Mt. Vesuvius seismic swarms |
Subject Classification: | 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology | Abstract: | The seismicity which affects Mt.Vesuvius is, at present, the only clear indicator of the volcano dynamics. In the last years, two periods of increased seismic activity occurred (August-October 1995 and March-May 1996). This seismicity was detected by the 10 analog stations of the Permanent Seismic Network as well as by up to 7 three-component temporary digital stations. A total number of about 600 events have been recorded, four of which showing magnitude >3.0. The maximum magnitude earthquake (M=3.4) was the strongest in the last fifty years and occurred on 25 April 1996. The use of three-component seismometers allowed us to obtain very reliable hypocentral locations. The focal volume of the two seismic crises does not exceed 5-6 km of depth below the crater area. Fault plane solutions of the most energetic events show focal planes oriented NW-SE and NE-SW, in agreement with the regional tectonic features, indicating that at present the seismicity of Mt.Vesuvius develops along pre-existing discontinuities. In addition, the occurrence of a fluiddriven source mechanism suggests a role played by the underground water on the seismic energy release. Shear wave splitting analyses confirmed the presence of an anisotropic volume related to a distribution of cracks andlor fractures parallely aligned to the main faults system of the volcano. |
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