Coincident anomalies of seismic attenuation and electrical resistivity beneath the southern Bolivian Altiplano plateau

Abstract

Reassessment of local earthquake data from the ANCORP seismological network allowed the calculation of 3D attenuation (Q p) tomographic images of crust and upper mantle beneath the southern Bolivian Altiplano around 21° S. The images reveal a low-Q p middle and lower crust and a moderate-Q p upper mantle beneath the southern Altiplano. Beneath the recent magmatic arc, Q p is not significantly decreased at this latitude. The distribution of crustal Q p coincides with the variation of electrical resistivity, thus limiting the possible mechanisms causing the anomalies. Our findings support the hypothesis that partial melts in middle and lower crust beneath the Altiplano are present on a large scale. We see no evidence for a shallow asthenosphere beneath the southern Altiplano.