Seismic surveillance in Portugal

M. Luisa Senos1, Fernando Carrilho2, Paulo Alves3
1, 2Instituto de Meteorologia, Rua C, Aeroporto, 1700 Lisboa, Portugal.
Tel. : +351-1-8483961, Fax: +351-1-8402370,
E-mail: sismologia@meteo.pt
3Observatório Afonso Chaves, Instituto de Meteorologia, Relvão, 9500 Ponta Delgada, Açores, Portugal.
Tel. : +351-96-653809, Fax +351-96-653288,
E-mail: sivisa@mail.telepac.pt

Portugal Mainland is located in a moderate seismic area. Nevertheless it was affected by catastrophic events such as those of November 1, 1755 and April 23, 1909. The Institute of Meteorology monitors the national seismic activity with digital and analogue seismograph networks. Some regions with more activity are also monitored with local networks. Altogether there are 30 stations in permanent operation.

The Azores Islands, near the triple junction in the North Atlantic Ocean, are characterised by a high level of seismicity and long seismic swarms. Earthquakes such as those of October 22, 1522, July 9, 1757 and January 1, 1980 resulted in dramatic number of casualties. In this region the Institute of Meteorology, working in partnership with Azores University, operates 28 stations. A new regional digital network with 12 stations is being implemented. This will allow the reconfiguration of the actual analogue network mainly aimed at seismovolcanic surveillance. All data, collected in the different networks, are analysed, compiled and distributed to the users in monthly bulletins. The Civil Defence Service is in permanent contact with the Institute in case of felt earthquakes and during seismic swarms.