IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS007 Poster presentation 1969
Magnetic imaging of the feeding system of oceanic volcanic islands: El
Hierro (Canary Islands)
Dr. Isabel Blanco-Montenegro
Departamento de Fsica Universidad de Burgos IAGA
Iacopo Nicolosi, Alessandro Pignatelli, Massimo Chiappini
El Hierro is the youngest of the Canary Islands, a volcanic archipelago in the central Atlantic, near the
African coast. The subaerial part of the island shows a characteristic shape with three convergent ridges
that have been interpreted as a triple-arm rift system. These ridges are separated by wide, horseshoe
embayments, related with the occurrence of at least four giant landslides. Recent works based on highresolution
bathymetry, however, have shown that in the submarine portion of the island the rift
structure is much more complex. We have analyzed an aeromagnetic anomaly dataset acquired in 1993
by the Spanish Instituto Geogrfico Nacional in order to obtain a structural model of the island from a
magnetic point of view. A digital elevation model of the volcanic edifice was divided into a mesh of
prismatic cells, each of them with its top corresponding to the topographic height (or bathymetric
depth, in the marine area) and its bottom at the constant depth of 4000 m below the sea level. A threedimensional
(3D) inversion algorithm was applied to the magnetic anomaly data that has provided us
with a magnetization distribution containing valuable information about the inner structure of the island.
We have completed the study with a forward modelling along some representative profiles. The
magnetic model has allowed us to obtain new evidences about the rift structure of El Hierro. In
particular, high magnetization values have been interpreted as intrusion complexes on which rifts zones
are rooted. Their location confirms the hypothesis of a complex rift structure in the marine area,
suggesting that sometimes rift axes might be shifted with respect to previous interpretations. In
addition, the areas affected by giant collapses are characterized by very low magnetization values,
showing that magnetic anomalies can provide fresh information about this kind of catastrophic event.
Keywords: oceanic volcanic islands, magnetic anomalies, intrusion complexes