Publications

The central Andean plateau is a prime region to study mantle flow above an active plateau margin, where it has been suggested that there is a link between plateau uplift and removal of the lower crust and lithospheric mantle. The southern Puna plateau (25 S to 28 S) is characterized by a number of anomalous features with respect to the rest of the Puna-Altiplano plateau including a distinctive spatial and geochemical pattern of mafic lavas and giant ignimbrites, a high topography with a large deficit in crustal shortening, an underlying slab with a gap in teleseismic intermediate depth seismicity, and a transitional dip between a steeper segment to the north and a flat-slab to the south. To investigate mantle deformation patterns across this region a total of 43 US and 30 German broadband seismic stations were deployed across the southern Puna plateau. The region of study has the advantage of deep seismicity and intermediate depth seismicity at the edge of the array which will help to constrain the depth of an anisotropic layer(s) responsible for any shear-wave splitting. Using observations of both teleseismic and local shear-wave splitting, the depth dependence of azimuthal anisotropy beneath the Puna plateau can be constrained. The preliminary results of shear-wave splitting measurements from PKS, SKS, and SKKS phases show a fairly complex pattern of shear wave splitting throughout the southern Andean plateau. In general we observe trench parallel subparallel splitting extending from the back arc to the foreland fold and thrust belt. We also observe several small regions of apparent no splitting which might suggest the presence of vertical asthenospheric flow. There is also a region of complex splitting where there is a rotation of the fast directions that are consistent with a radial flow pattern.

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Robinson, D.; Sandvol, E.; Kay, S. M.; Comte, D.; Alvarado, P.; Heit, B.; Yuan, X. (2008): Seismic Anisotropy Beneath the Southern Puna Plateau. AGU 2008 Fall Meeting (San Francisco 2008).