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Features of crustal structure under the Canary Islands

1981; Elsevier BV; Volume: 55; Issue: 1 Linguagem: Inglês

10.1016/0012-821x(81)90082-0

1385-013X

E. Banda, J.J. Dan ̄obeitia, E. Surin ̄ach, Jörg Ansorge,

earthquake and tectonic studies

The data and interpretation of a seismic refraction project carried out in the Canary Islands in 1977 and 1979 are presented. The Moho is reached at about 15 km under Fuerteventura, Gran Canaria, and Tenerife whereas under Lanzarote a value of 11 km has been found. The velocity at the surface varies, even within one island, from 2.8 to 4.4 km/s. There are variations in the velocity of the main crustal layer under the volcanic deposits. A continuous velocity-depth function seems to be more appropriate for the island of Tenerife, contrary to Fuerteventura, Lanzarote and Gran Canaria which seem to have a layered structure. There is evidence for pronounced structural differences between Lanzarote and Fuerteventura. The mantle velocity has a value of about 8.0 km/s under the western islands whereas a very low value of 7.4 km/s has been found under Lanzarote and Fuerteventura. Despite the clear structural differences between the islands our results leave little doubt about the oceanic character of all the islands. The differences between the eastern and western group may be due to the islands being situated close to the African continental margin. The seismic velocities under the volcanic deposits do not support the idea of a common basement for all the islands; they rather suggest independent volcanic edifices. Finally, a comparison of the structure of the crust under the Canary Islands with that under other volcanic islands reveals remarkable similarities.