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Instituto de Investigação
em Vulcanologia e Avaliação de Riscos
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Referência Bibliográfica

SENOS, M.L., GASPAR, J.L., ALVES, P. (2001) - A Sismicidade Recente do Arquipélago dos Açores. “2º Simpósio de Meteorologia e Geofísica da APMG”. Évora, 12 - 15 de Fevereiro (Comunicação Oral).


The Azores Archipelago is a high seismicity region, consequence of its geographical location, nearby the triple point of the Eurasian, African and American plates. This seismicity can appear as seismic swarms (between several hours and several years) associated or not with destructive events.
The most significant earthquake of the last decade happened on July 9, 1998, 16 km to NE of Horta (Faial Island). The Richter magnitude was 5.8 and the observed maximum intensity in the Mercalli Scale (1956) was VIII in the NE Zone of Faial Island. In that area some villages were almost totally destroyed.
Concerning the seismic swarms they can be grouped in two different types: or the crisis begins with the most violent event being followed by a long set of progressive less energetic events; or the crisis is constituted by several events of different energies with the most energetic event happening after some time of the beginning of the crisis. Some examples of crises of the first type are Banco Dom João de Castro (1997 / 98) and Faial (1998 till present). Faial (1992 / 93) was a good example of the second type of crisis.
These varieties in the seismic patterns show the importance of a systematic study of certain seismic parameters that could define the seismic behaviour of this region in such a way that the consequences of the most destructive events could be minimised.