Global Volcanism Program Volcanoes of the World Sete Cidades Volcanic Activity Reports
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Located at the W end of the Azores island of San Miguel, Sete Cidades contains a 5-km-wide summit caldera with green and blue lakes. The caldera was formed 22,000 years ago, and there have been about22 post-caldera eruptions. A number of submarine vents off the coast of San Miguel have been reported since the 1600's, the most recent in 1880.

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09/98 (BGVN 23:09) Seismic swarm on submarine flank

Since June 1998, increasing seismic activity in the vicinity of Sete Cidades volcano has resulted in occasional seismic swarms. On the night of 2-3 August about 120 events were registered in 3 hours. During that period, five earthquakes were felt along the W coast, the strongest with a magnitude of 3.1 reached a maximum intensity of V (MM) at Ginetes e Varzea. Similarly, on 2 September in Sao Miguel more than 120 events occurred beneath the sea floor over a period of about 4 hours near shore between Ponta da Ferraria and Mosteiros. One of the five felt earthquakes during this period also reached an intensity of V (MM). There were no reports of injury or damage from any of these events.

Located at the W end of the Azores island of San Miguel, Sete Cidades contains a 5-km-wide summit caldera with green and blue lakes. The caldera was formed 22,000 years ago, and there have been about22 post-caldera eruptions. A number of submarine vents off the coast of San Miguel have been reported since the 1600's, the most recent in 1880.

Information Contacts: João Luis Gaspar (Email: jlgaspar@alf.uac.pt) and Nicolau Wallenstein (Email: nw@mail.telepac.pt), Departamento de Geociencias, Centro de Vulcanologia, Universidade dos Açores, Rua Mae de Deus, 9500 - Ponta Delgada, Sao Miguel, Açores, Portugal.

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