Madeira, J. & Brum da Silveira, A. (2007), Tectónica e sismicidade na ilha do Faial e o sismo de 9 de Julho de 1998. Boletim do Núcleo Cultural da Horta,16: 61-79. |
Madeira, J. & Brum da Silveira, A. (2007), Tectonics and seismicity in the island of Faial (Azores) and the 9th of July 1998 earthquake. Boletim do Núcleo Cultural da Horta,16: 61-79. |
Like the remaining islands in the central and eastern groups of the Azores, Faial is subject to frequent earthquakes. Sometimes those are distant events without any consequences for the island: however, the island is occasionally struck by local earthquakes that in some cases, cause destruction and casualties. Since settlement, in mid 16th century, until the beginning of the 20th century, Faial has been preserved from destruction by earthquakes. But in 1920, 1924, 1926, 1958 and 1998 the population of the island was confronted with destructive earthquakes and seismic swarms. However the island’s morphology is marked by the scars of numerous seismic events of moderate to high magnitude that affected its topography in pre-historic times. Reading the geologic record through the use of neotectonic and paleoseismology techniques revealed the occurrence of clusters of earthquakes in time. The clusters are separated by periods of the order of 500 years. That time interval is comparable to the period since the settlement and the beginning of the last century (approximately 470 years), after which a cluster of earthquakes and seismic swarms occurred in about 80 years. The most recent of those events, the earthquake of the 9th of July, 1998, was one of the most destructive. Its effects on the buildings and infrastructures and the physical modifications caused in the topography of Faial are described. Finally, some considerations on the seismic hazard and risk in the island of Faial and the Azores archipelago are made. |
