Long-term versus short-term deformation processes at Tenerife (Canary Islands)

摘要

Several geophysical investigations have identified that the Tenerife volcanic complex is affected by crustal deformation processes occurring at timescales of millions of years. Recently, space-based geodetic observations have also detected a short-term surface deformation, characterized by a broad subsidence pattern with maximum ground velocities of about 4 mm yr-I. For the purpose of investigating the relationship between these long-term and short-term deformation processes, we performed an advanced fluid dynamic analysis (FDA). We first carried out a standard dimensionless FDA to discriminate the deformation style of Tenerife and found that, at million year timescales, basement flexure mainly controls its long-term structural evolution. Secondly, to highlight the driving forces of the short-term deformation process, we simulated a numerical FDA based on finite element models that include topography as well as vertical and lateral material heterogeneities. Our results show that the recent surface deformation is mainly caused by a progressive sagging of the denser (less viscous) core of the island onto the weaker (but more viscous) lithosphere. Moreover, over periods comparable to the hypothesized age of loading of the oceanic crust beneath Tenerife, this tendency would result in a total flexure of about 3-4 km, which is in agreement with independent estimations based on geophysical analyses. Our study shows that a unitary physical model may explain both the deformation recorded in deep geological structures and the current active ground deformation processes occurring at the Tenerife volcano.