Bezzeghoud, Mourad

Borges, José Fernando

Caldeira, Bento

Carvalho, Alexandra

Carvalho, João P. G.

Neves, Samuel

Laboratório Nacional de Energia e Geologia Repository

Near-surface wave velocity structure of Faial (Azores - Portugal) Island for site effect studies

Carvalho, João

Repositório do LNEG

Geophysical Research AbstractsVol. 17, EGU2015-12509, 2015EGU General Assembly 2015© Author(s) 2015. CC Attribution 3.0 License.Near-surface wave velocity structure of Faial (Azores – Portugal) Islandfor site effect studiesJosé Borges (1), Samuel Neves (2), Bento Caldeira (1), Mourad Bezzeghoud (1), João Carvalho (3), andAlexandra Carvalho (4)(1) Instituto de Ciências da Terra; Departamento de Física, Escola de Ciências e Tecnologia, Universidade de Évora, (2)Universidade de Évora, (3) Laboratório Nacional de Energia e Geologia, Lisboa, Portugal, (4) Laboratório Nacional deEngenharia Civil, Lisboa, PortugalThroughout history, the life of the Azorean people has been marked by earthquakes that have had different effectsdepending on their proximity and magnitude. This seismic activity, which may have volcanic or tectonic origins,has affected the population of these islands by destroying infrastructure and claiming lives. The social and eco-nomic impacts of these phenomena are enormous. The last significant event affecting the Azores (Portugal) wasthe July 1998 Mw=6.2 earthquake causing major destruction affecting more than 5000 people, causing 8 deaths,150 persons injured and 1500 homeless. Ground motion simulations are mainly based on source characteristicsand are heavily dependent on the medium, which is still poorly understood. Subsurface soil condition can amplifythe seismic waves, so, for seismic response analysis, it is necessary to know the shallow soil properties and itsspatial variability. For this purpose, we applied P and S-wave refraction, Multichannel Analysis of Surface Waves(MASW) to characterize shear wave velocity at different sites in the Faial Island, in particular, in sites where al-ready occurred amplification. Ambient vibrations can also be used to estimate physical properties of the shallowergeological formations. With this goal, the obtained velocity models were confirmed by comparison between realH/V curves with synthetic ones. We concluded that the anomalous intensities observed in some sites are stronglyrelated to thick layers of soft sediments of pyroclastic deposits produced by old volcanic eruptions occurred in theFaial Island.

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Near-surface wave velocity structure of Faial (Azores - Portugal) Island for site effect studies

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