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Referência Bibliográfica


OKADA, J., TROTA, A., RODRIGUES, R., FERREIRA, T., GASPAR, J.L. (2010) - Volcanic and Tectonic Controls Revealed from GPS Observations in S. Miguel Island, Azores. 6th Cities on Volcanoes (Comunicação Oral).

Resumo


The Azores archipelago is located across the Mid-Atlantic Ridge, where three tectonic plates meet such as African (Nubian), North American and Eurasian plates. The archipelago has many active volcanic systems. Among them, the Monte Escuro-Congro area, located in the NE flank of Fogo (Agua de Pau) volcano in the central part of S. Miguel Island has been recognized as one of the most active seismo-volcanic fields in the Azores. This area has been repeatedly suffered from significant earthquake swarms, e.g. in 1989 and in 2005 for last few decades, thus has provided good research opportunities for understanding the relations between seismic swarms and potential eruptions. The 2005 event was successfully observed with GPS network operated by CVARG (Center of Volcanology and Geological Risks Assessment, University of Azores). Previous seismological and geodetic researches have given strong suggestions for magmatic intrusions without resulting in any eruption episodes in the area. The smaller earthquakes have still existed after 2005 episode in the Monte Escuro-Congro area and its vicinity. In this study, the recent GPS data sets including 9 permanent GPS stations (7 operated by CVARG and 2 by regional government) have been processed using Bernese software v5.0 to evaluate ongoing volcanic and tectonic activities in the island. Preliminary results indicate the stress relaxation after 2005 episode and resumed deformation activities on the east part of Fogo volcano. The west part of Fogo volcano seems quiet both in deformation and seismic activities. This contrast suggests the existence of a local tectonic boundary which can make magma movement upward more feasible and cause occasional swarm episodes (likely as “failed eruptions”) in Monte Escuro-Congro area. Implementation of the permanent GNSS network has played an important role for seismo-volcanic risks assessment in the Azores.

Observações


Anexos