Velocity and Anisotropic Structure of the Uppermost Mantle Beneath Central America and Northwestern South America From Pn Tomography

Abstract

AbstractWe constructed the first Pn velocity and anisotropy model of the uppermost mantle in Central America and northwestern South America using the Pn tomography method and new ISC‐EHB data. Significantly low Pn velocities and arc‐parallel anisotropic structures are observed beneath the volcanic arc in Central America. The separate, low Pn velocity beneath the back‐arc volcano in Nicaragua shows that the hot material upwelling in the uppermost mantle beneath this volcano is likely separated from the main volcanic arc. The stable Caribbean Plate is characterized by high Pn velocities. The southward subduction and dehydration of the Caribbean Plate seem to be potential causes of the low Pn velocities in eastern Panama. Based on our Pn velocity, anisotropy and previous geological observations, we suggest a dynamic model of the Colombia‐Ecuador region including mantle flow and magmatic gap: there is arc‐parallel anisotropy in the uppermost mantle beneath the Colombia‐Ecuador volcanic arc, arc‐perpendicular mantle flow in the deeper mantle beneath the subducted plate, and a magmatic gap near the Caldas Tear.