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Instituto de Investigação
em Vulcanologia e Avaliação de Riscos
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Referência Bibliográfica

FERREIRA, T., GASPAR, J.L., VIVEIROS, F., MARCOS, M. (2003) - Fluid geochemistry monitoring in the Azores archipelago: A review. ESF LESC Workshop on “Gases in magmatic evolution: from depth to atmosphere, from micro to macro-scale, from calculation to observation”. Italy, Rome, 10-14 de Maio (Comunicação Oral).


The Azores archipelago is located in the Atlantic Ocean and consists of nine volcanic islands. This region shows an important seismovolcanic activity due to its complex geological setting dominated by the existence of a mantle plume in the area where the American, African and Eurasian lithospheric plates meet [Searle, 1980].
Throughout more than five hundred years of history about thirty important destructive earthquakes have been reported in the archipelago, causing thousands of deaths and severe damages. The instrumental data for the last twenty years of activity clearly demonstrates that almost all the seismicity in the Azores region took place along the Terceira Rift and the Mid-Atlantic Ridge. Twenty-eight historical volcanic eruptions took place in the same time period along the Terceira Rift [Weston, 1964; Gaspar et al. 2003].
The Azores University Volcanological Observatory assures the volcanological monitoring of the Azores area using geophysical, geodetic and geochemical techniques. Geophysical monitoring includes the management of a seismological network composed by more than 40 seismic stations and is performed in collaboration with the Meteorological Institute. Geodetic monitoring is based on a GPS network formed by several permanent receivers and complemented by regular GPS field surveys. Fluid geochemistry monitoring involves the regular sampling and analysis of gas discharges in fumaroles [e.g. Ferreira and Óskarson, 1999], hot springs [e.g. Cruz et al., 1999] and geothermal and water wells, as well as the study of diffuse soil gas emissions [Baubron et al., 1994]. The main fumarolic fields and hot springs under monitoring are associated to some of the active central volcanoes located at S. Miguel, Terceira and Graciosa islands. Geothermal wells are situated in Fogo Volcano, at S. Miguel island. In the last years several CO2 and Rn soil diffuse degassing surveys were performed in S. Miguel, Terceira, Graciosa and Faial islands both for seismovolcanic and public health risk assessment [Faria et al. 2003; Gaspar, 1996]. Continuous monitoring of CO2 soil flux is being carried out in such islands taking in account the influence of the meteorological parameters [Viveiros et al., 2003].
Data obtained by all the permanent monitoring networks are transmitted to the Azores University Volcanological Observatory, in S. Miguel Island, and processed in a daily basis in order to evaluate the seismovolcanic levels of activity and inform the Azores Civil Protection.