Fieldwork in the Azores

Vila Franca ok x Blog
Vila Franca do Campo, Saõ Miguel, Azores (PForlin).

Located in correspondence with the Eurasian, Nubian and North American plates triple junction, the Azores represent one of the most seismically active areas of the Atlantic Ocean.

On October 22nd, 1522, a Mw 5.0-5.9 earthquake triggered several landslides on the island of Saõ Miguel. The largest one was activated by an active fault identified east of the Fogo volcano on the Achada das Furnas plateau (Carmo et Al. 2013). This mass movement, the volume of which has been calculated as 6.75×106 m3 with an extension of 4.5 km2 (Marques et Al. 2009), buried most of the settlement of Vila Franca do Campo, then-capital of Portuguese Azores, killing ca. 5000 people according to contemporary sources (Frutuoso 1981).

Archaeological investigations carried out during the 1960s and ‘70s by a local archaeologist, Sousa d’Oliveira (Bento 1989), identified several remains of the old settlement, laying at a depth of between 2 and 5 m underneath the actual surface. However, the quality of the archaeological documentation was not detailed, and what we know better thanks to this research is the positioning of the finds. Only very approximate plans and sections were instead produced.

Bento_p19
Plan from Bento 1989, p.19

Nevertheless, the site presents a very high archaeological potential, as most of the ancient Vila Franca do Campo remains possibly still preserved below this mass movement deposit.

Preliminary fieldwork conducted in collaboration with José Bettencourt (University of Lisbon) in November, gave us the opportunity to cross-reference available archaeological and palaeoenvironmental information, as shown by the attached GIS map. A first evaluation of the archaeological deposit distribution has therefore been assessed in order to consider possible future research.

Vila Franca GIS_2
Map showing the distribution of the archaeological sites found by Oliveria in relationship with the landslide that buried the old Vila Franca do Campo in 1522 (according to Marques et al. 2009). Map: P. Forlin

This case study allows us to open an exceptional window on the effects of the seismic event, but also on the reaction activated by the local population. Since the ‘new’ Vila Franca do Campo was funded along the western side of the landslide (for instance, the convent of São Francisco was built immediately after the earthquake in 1522), this context can be seen as an extraordinary example of resilience of that community, who again faced another destructive earthquake in 1536.

References

Bento, C. M. (1989) – Escavações Arqueológicas em Vila Franca do Campo 1967-1982, São Miguel, Associação Arqueológica do Arquipélago dos Açores

Carmo R., Madeira J., Hipólito A., Ferreira T. 2013, Paleoseismological evidence for historical surface faulting in São Miguel island (Azores), ANNALS OF GEOPHYSICS, 56, 6, 2013, S0671; doi:10.4401/ag-6221

Frutuoso, G. (1522-1591†). Livro Quarto das Saudades da Terra, in Saudades da Terra, G. Frutuoso (Ed.), 2a ed., Ponta Delgada, Instituto Cultural de Ponta Delgada, II, 1981

Marques R., Zêzere J.L., Gaspar J.L., Amaral P. 2009, Reconstituição e modelação probabilística da escoada detrítica de Vila Franca do Campo desencadeada pelo sismo de 22 de Outubro de 1522 (S. Miguel, Açores), Publicações da Associação Portuguesa de Geomorfólogos, Volume VI, APGEOM, Braga, 2009, p. 175-182

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