Anatomy of the Colima volcano magmatic system, Mexico

Abstract

Colima volcano is one of the most active volcanoes in continental north America. It is located within the Colima graben on the western part of the Colima rift zone. Although extensively studied, the internal structure and deep magmatic system remains unknown. This research gives new clues to understand how and where magmas are produced and stored at depth. Using ambient seismic noise, we jointly invert for Rayleigh and Love wave dispersion curves for both phase and group velocity, which is applied for the first time in a volcanic environment. We invert for both the shear wave velocity and radial anisotropy. The 3D high resolution shear wave velocity model shows a deep, large and well-delineated elliptic-shape magmatic reservoir below the Colima volcano complex at a depth of about 15 km. On the other hand, the radial anisotropy model shows a significant negative feature (i.e., VSV>VSH) revealed from ≥35 km depth until the top of the magma reservoir at about 12 km depth. The latter suggests the presence of numerous vertical fractures where fluids, rooting from a well-known mantle window, can easily migrate upward and then accumulate in the magma reservoir. Furthermore, the convergence of both a low velocity zone and a negative anisotropy suggests that the magma is mainly stored in conduits or inter-fingered dykes as opposed to horizontally stratified magma reservoir.