Spatial Variation of Mantle Velocity Discontinuities across South America


By combining data from three broad band portable seismic networks, systematic variations in the depths of the Moho, the 410 km, and 670 km discontinuities have been revealed across the South American continent at approximately 20 degrees South latitude. Non-linear stacking of high quality radial receiver functions from 989 events, recorded by 40 broadband stations from 3 portable seismic networks (BANJO, BLSP, and SEDA) are used to study lateral variations in the depth and sharpness of major discontinuities. The most significant features are the dramatic variation of the depth to the Moho over the profile, and that of the 670 km discontinuity below and above the subducting slab. West of the Andes, the depth to the Moho is about 40-45 km, It increases to 65-80 km over a distance of less than 50 km, and then decreases to about 45-50 km beneath the eastern boundary of the Andes, over a distance of about 120 km. Further east, the depth to the Moho continues to decrease, reaching 38 km at approximately at a longitude of 58⁰W. Beneath a cratonic area at 51⁰W it thickens to 45 km. From 49⁰W to 44⁰W the depth decreases from 42 to 36 km. While the depth of the 410km discontinuity is about the same (410-420km) across the profile, the depth of the 660km discontinuity shows significant variations. Beneath the western part of the profile, approximately from 67⁰W to 59⁰W, the depth is in the range of 700-710km; and beneath the eastern part, it changes to 670-680km over a distance of about 300 km. The geodynamic significance of these observations will be presented.

Meeting Name

AGU Fall Meeting (1999: Dec. 1, San Francisco, CA)


Geosciences and Geological and Petroleum Engineering

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Article - Conference proceedings

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© 1999 American Geophysical Union (AGU), All rights reserved.

Publication Date

01 Dec 1999

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