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Plate Boundary and Volcano Deformation in the Azores Analysed by Satellite-based Geodetic Techniques


​​Ground deformation in the Azores, at the triple junction between the Eurasian, Nubian, and North American plates, has been mapped with GNSS (Global Navigation Satellite System) and InSAR (Interferometric Synthetic Aperture Radar) satellitebased geodetic measurements to improve tectonic motion estimates and for understanding volcanic unrest. Time dependent coordinates, spanning a maximum of more than 20 years (2000-2022), from more than 100 GNSS stations were computed and analyzed. Of these GNSS stations, about 20 were operated continuously across the Azores, and 80 were operated episodically on the São Miguel Island. InSAR data from São Miguel Island (2017-2019) and São Jorge (2022) was analyzed. Results from the continuous GNSS stations show that the Eurasian-Nubian plate boundary in the Azores behaves as a diffuse ultra-slow oblique spreading center with focused deformation found in the Central Group and São Miguel islands. The velocity field obtained from data of the continuous GNSS stations (2000-2016) was modeled by approximating segments of the Eurasian-Nubian plate boundary with vertical rectangular dislocations with rightlateral motion and opening below a locking depth. Best-fit models have a deep motion that accounts for almost half of predicted Eurasian-Nubian relative plate motion. The velocity field obtained from data of the GNSS stations of São Miguel Island (2004-2016) shows in more detail the spreading focused in the central area of the island. Inferred ground deformation from GNSS data from São Miguel Island shows transient volcanic deformation in Fogo volcano, with periods of inflation in 2004-2006, 2011-2013, and a deflation period in 2013-2016. The velocity field from Fogo volcano was modeled using sources of pressure change embedded within uniform elastic half-space. The best fit modeled sources are located near the eastern and northeastern rim of the Fogo caldera, and to the east of it, at depths of 3.2-3.7 km. A combined GNSS and InSAR data analysis shows renewed inflation at Fogo volcano in 2018-2019. A combined analysis of GNSS and InSAR data reveals that at São Jorge Island in 2022, after 60 years of repose, magma reached almost the surface within a few hours of the seismicity onset with no precursory signals. Results from analysis of geodetic data show that a sudden diking event occurred below São Jorge Island, with transient deformation recorded over two weeks and higher seismicity recorded during months after the start of the activity. The geodetic data from São Jorge was modeled using a segmented vertical dyke with multiple opening patches, with best-fit results indicating a maximum opening of more than one meter in two different areas, at 4-6 km and 7-9 km depth. ​

Ficha de Projeto

Bolsa de Doutoramento SRMCT/FRCT

Plate Boundary and Volcano Deformation in the Azores Analysed by Satellite-based Geodetic Techniques
Bolseiro: João D'Araújo

Entidade financiadora: FRCT

Referência nº: ACORES-10-5369-FSE-00000
Duração: 2017-2021

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