Lithospheric structure of the central Andes based on surface wave dispersion

David Baumont (1) , Anne Paul (2) , George Zandt (3) , Susan L Beck (3) , Helle Pedersen (1)

1 LGIT - Laboratoire de Géophysique Interne et Tectonophysique
2 ISTerre - Institut des Sciences de la Terre
3 University of Arizona

Shear wave velocity is very sensitive to temperature anomalies and partial melt and can provide important insights on the state of the lithosphere. With that aim in mind, phase velocities of Rayleigh and Love waves have been inverted for the regionalized shear wave velocity structure of the lithosphere across the central Andes. This inversion reveals strong lateral variations of V s both across the range and along-strike in the Altiplano crust. In the upper crust, the main features of our models are prominent low-velocity anomalies probably related to partial melt below the Los Frailes ignimbrite complex and the southern Altiplano. At lower crustal level, the Altiplano is characterized by lower V s than the surrounding regions. We find that the transition from the Altiplano to the Puna is associated with a 7-km thickening of the crust. At mantle depths, the Nazca plate is found to be overlaid by a dipping low-velocity zone with decreasing intensity with depth. Our results favor the idea of a cold mantle lid underlying the whole central Andes.

Mots clés: Andes; surface waves; lithosphere; Vs; subduction

Domaines: Géophysique [physics.geo-ph]

David Baumont, Anne Paul, George Zandt, Susan L Beck, Helle Pedersen. Lithospheric structure of the central Andes based on surface wave dispersion. Journal of Geophysical Research : Solid Earth, 2002, 107 (B12), pp.ESE 18-1-ESE 18-13. ⟨10.1029/2001JB000345⟩. ⟨hal-02156825⟩