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Instituto de Investigação
em Vulcanologia e Avaliação de Riscos
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Referência Bibliográfica

MATIAS, M., SILVEIRA, G., DIAS, N., SILVA, P., GASPAR, J.L., MIRANDA, M., SENOS, M.L., FERREIRA, T., FARIA, C. (2002) - MASHA Multi-scale approach for seismovulcanic Hazard in the Azores. Azores. “II Momar Workshop”. Faial, Horta, 15 - 17 de Junho (Poster).


MASHA is a project dedicated to study the processes that constrain and shape the volcanic and seismic hazard of the Azores area, using seismic and geochemical monitoring. The MASHA is structured as a multi-scale scientific approach to investigate the earth processes at: the regional scale – the Azores mantle plume and hot spot; the mesoscale – the crustal structure; and the local scale – the tectonic and volcanic structures that directly affect the island populations.
The first scale regards the study of the regional setting, mainly the anomalous lithosphere and astenosphere structure of the Azores and its contribution to the episodic volcanic and seismic activity. The study will be conducted using data from two very broad band (VBB) seismic stations, complemented with island VBB stations installed under the umbrella of the Memorandum of Understanding-COSEA (COordinated Seismic Experiment in the Azores) plus data from CMLA already operating in S. Miguel. The large-scale network will provide tomographic images of the area with a resolution around 200 km.
The Mesoscale – 10’s of km – regards crustal scale studies namely the seismic anisotropy, its correlation with crustal strain as well as its relationship with seismic and volcanic events. This study will be achieved by studying data acquired by short period and broadband seismic sensors.
The local scale – 1 km – regards the assessment of seismic and volcanic hazard, in the area of Faial, Pico and S. Jorge Islands. This area has been chosen due to its particular environment: 1) it is affected by a seismic crisis initiated in July 1998 with the source area well covered by seismic stations; 2) preliminary observations of geochemical parameters in Faial show a relationship between gas emanations and seismic activity. In order to correlate seismic and volcanic data acquired from independent sources, this project includes specific studies on seismicity pattern of the Faial crisis and a dedicated geochemical monitoring program in the Faial Island. The previous activities allowed the selection of the most sensible observation sites and the variables to be monitored.
The concurrence of: i) a operating pool of VBB instruments (COSEA Agreement); ii) the operation of a wide SP digital network since 1998; iii) the well constrained seismo-volcanic activity that occurs in the Faial channel; make this project a unique opportunity to study the multi-scale interaction between seismic and volcanic processes in the Azores. These conditions will not be easily met in the future.
We present some preliminary results obtained in the framework of the project.