The crustal structure of El Hierro (Canary Islands) from 3-D gravity inversion

摘要

El Hierro is the youngest and westernmost island of the Canarian Archipelago. Due to its singular and interesting characteristics, with extensive landsliding, studying its crustal structure can provide very useful information about its origin and evolution. With this aim, we use the gravity inversion methodology obtaining a crustal model of mass distribution. We performed a gravity survey of the entire island, completing the gravity anomaly map of this area with marine data from the United States Geological Survey. The calculated Bouguer gravity anomaly map was studied using a covariance analysis and the least squares technique. To obtain crustal information from these data, we used a 3D gravity inversion based on genetic algorithms (GA). Thus, our inversion technique aims to determine the geometry of the sources of the observed gravity field, upon a prismatic partition of the subsoil volume, and adopting a priori density contrast values. The results of this gravity study of El Hierro Island show the correlation of several volcanic structures with the distribution of the gravity field sources. The characteristic triple rift system of the island is associated with low-density areas, and the older volcanic stages with high-density structures. We also found differences among the structures related to the several landslides, which helped the island takes shape.