HR: 1330h
AN: V23A-01    [Abstracts]
TI: Historical Earthquakes and Expected Seismic Damage at Ischia Island, Resurgent Caldera (Southern Italy)
AU: * Carlino, S
EM: stefanocarlino@email.it
AF: Osservatorio Vesuviano-INGV, V. Diocleziano,328, Naples, 80124 Italy
AU: Cubellis, E
EM: cubellis@ov.ingv.it
AF: Osservatorio Vesuviano-INGV, V. Diocleziano,328, Naples, 80124 Italy
AB: Information on the seismicity of the Ischia island spans about eight centuries, starting from 1228. This is characterized by the occurence of earthquakes with low energy and high intensity. The most recent earthquake of 1883 caused 2333 deaths and the destruction of the historical and environmental heritage of some areas of the island, specially at Casamicciola town. This event (Imax = XI degree MCS), represents an important date in the prevention of natural disasters, in that it was after this earthquake that the first Seismic Safety Act in Italy was passed. After the 1883 earthquake there was a period of seismic quiescence except for some isolated events felt at beginning of the last century and the very occasional micro-earthquakes recorded in the last 20 years in the northern part of the island. The epicenter of all known earthquakes are on the northern slope of Mt. Epomeo (787 m a. s.l.) resurgent block, while analysis of the effects of earthquakes and the geological structures allows us to evaluate the stress fields that generate the earthquakes. The Mt. Epomeo is a resurgent structure in the central sector of the island, whose uplift is correlated to the caldera resurgence process, for the increase of pressure of shallow magma reservoir. The caldera was formed after a large explosive eruption that deposited the Mt. Epomeo Green Tuff, about 55 ka B.P. The uplift, which started about 30 ka B.P., was of about 900 meters. The resurgent structure is bordered by a system of faults and fractures, with NW-SE, NE-SW and N-S strike and along these faults, in the northern sector, the seismicity has been localized. In a volcanic area, interpretation of the mechanisms of release and propagation of seismic energy is made even more complex as the stress field that acts at a regional level is compounded by that generated from migration of magmatic masses towards the surface, as well as the rheologic properties of the rocks dependent on the high geothermic gradient. Such structural and dynamic conditions make the island of Ischia a seismic area of considerable interest. Thus a seismic hazard map of the island is proposed, according to a comparative analysis - using GIS - of various types of data: the geology, tectonics, historical seismicity, damage caused by the 28 July 1883 Casamicciola earthquake and the source model.
DE: 7215 Earthquake parameters
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
DE: 7280 Volcano seismology (8419)
DE: 8123 Dynamics, seismotectonics
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2005 Joint Assembly