Seismic hazard analysis in zones of time and space interdependence: An application to S?o Miguel Island, Azores |
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| Authors: | C S Oliveira A C Costa V H Forjaz and J C Nunes |
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| Institution: | (1) Laboratório Nacional de Engenharia Civil (LNEC), Av. Brasil, 1799 Lisbon, Portugal;(2) Centro de Vulcanologia, (CV), INIC, Universidade dos Açores, Azores, Portugal;(3) Instituto Nacional de Meteorologia e Geofisica (INMG), Lisbon, Portugal |
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| Abstract: | The Azores Islands are located in the mid-Atlantic region near the triple junction where the Euro-Asiatic-African-American plates join together. Seismic activity in the area is very high, as can be observed either from historical events since the fifteenth century, from present day microseismicity, and from direct and indirect measurements of recent tectonic deformation. Volcanic activity is also present throughout the region.All available information, even data exhibiting low quality, was used to develop hazard models of São Miguel Island. Source zones were established based on both the global tectonic behaviour of the region and on the local active fault structures. Recurrence laws for São Miguel Island, for which historical information seemed quite incomplete, were obtained from the large events in the entire archipelago and from their remarkable pattern of time and space dependence, and complimented by information on long-term fault deformation (for the longer recurrence periods) and on high precision instrumental network (for the very short recurrence periods).Attenuation laws were derived from data on events felt and/or recorded in the Island.Hazard maps were obtained through a modified version of McGuire's algorithm for several geometries of source areas and results compared with the maximum observed intensity of historical events.Abstract presented at the 21st General Assembly of the European Seismological Commission held in Sofia, 1988. |
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| Keywords: | Hazard analysis recurrence probability of exceedence zoning uncertainties time-space interdependence |
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