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Instituto de Investigação
em Vulcanologia e Avaliação de Riscos
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Referência Bibliográfica

MARQUES, R., GASPAR, J.L., ZÊZERE, J.L., SILVEIRA, D., MALHEIRO, A. (2004) - Mapping and characterization of the landslide induced by the 1522 Vila Franca do Campo earthquake (S. Miguel island, Azores). EGU 1st General Assembly, Nice, France,  25 - 30 de Abril (Poster).


Since the settlement of S. Miguel Island, in the 15th century, heavy rainfall episodes, earthquakes and volcanic eruptions induced several destructive landslides. The most important earthquake in the region occurred on the 22nd of October 1522. It was suggested that such event had epicenter on land, a few kilometers NNW of the former capital of S. Miguel Island, Vila Franca do Campo, reaching a maximum intensity of X (EMS-98). The earthquake triggered several landslides mostly of debris flow type and it was reported the occurrence of a small tsunami. As result of this coupled geological event about 5000 people died and the village of Vila Franca do Campo was completely destroyed. Some of the boats anchored near Vila Franca islet, 2 km offshore, were damaged.


In order to characterize the 1522 landslide episode, a detailed study was carried out comprising the analysis of historical documents, aerial photographs and field observations. The produced debris flows are well constrained in the regional stratigraphy, being covered by the ash and lapilli of the 1630 Furnas eruption. The deposit is highly variable in thickness and is heterogeneous considering the nature and dimension of its components. The matrix is fine-grained and mainly composed by pumice, containing a significant amount of basaltic, trachytic and syenitic fragments, as well as a considerable quantity of feldspar crystals. In some outcrops, archaeological artefacts from the 16th century were found. The interpretation of the available data allowed inferring the source of the main debris flows as well the reconstruction of the deposition areas.


The obtained results can be taken into account to implement strategies for land-use planning aiming to minimize the impact of future events.