Recurrent seismic activity on Graciosa island was considered to be above normal according to the Center of Volcanology and Geological Risk Assessment (CVARG)at the University of the Azores.
Three seismic events, magnitudes II and III on the modified Mercalli scale, were felt during the week in the southwestern areas of Almas, Guadalupe, Ribeirinha and Pedras Brancas on the island. A fourth seismic event, maganitude III on the modified Mercalli scale, was also registered Saturday, March 10, at southwest of Vitória.
Last October, experts in the Azores alerted the population of São Miguel island for seismic activity which they also considered to be above normal. The seismic events where located in the system of Fogo and Congro lakes, the central region of the island.
The Azores are sitting on the so called “Azores triple junction” area where the North American, Eurasian and African plates meet. This area is responsible for frequent geological and volcanic activity on the islands.
The most recent serious seismic crisis occurred July 9, 1998, on the islands of Faial, Pico and São Jorge when an earthquake, measuring 5.8 on the Richter scale, destroyed hundreds of dwellings and killed nine people.
On January 1, 1980, an earthquake of tectonic origin, measuring 7 on the Richter scale, rocked the islands of Terceira, Graciosa and São Jorge. This major earthquake killed more than 60 people and destroyed hundreds of residences, leaving thousands of people homeless on all three islands.