Anomalous Crust of the Bolivian Altiplano, Central Andes: Constraints from Broadband Regional Seismic Waveforms

G. Zandt, S. L. Beck, S. R. Ruppert, C. J. Ammon, D. Rock, E. Minaya, T. C. Wallace, P. G. Silver

Research output: Contribution to journalArticle

54 Scopus citations

Abstract

A one-year deployment of broadband seismographs in the Bolivian Altiplano recorded numerous intermediate-depth earthquakes at near-regional distances. We modeled the associated broadband waveforms of two earthquakes to estimate an average crustal structure for the Altiplano. The resulting model is characterized by an anomalously low mean P velocity of 6.0 km/s, a low Poisson's ratio of 0.25, and a crustal thickness of 65 km. The combination of the low mean velocity and low Poisson's ratio can be explained only by a predominantly quartz-rich, felsic bulk composition. This constraint precludes significant volumes of magmatic addition from the mantle contributing to the great thickness of the Altiplano crust, but is consistent with thickening by compressive shortening concentrated in a weak felsic layer.

Original languageEnglish (US)
Article number96GL00967
Pages (from-to)1159-1162
Number of pages4
JournalGeophysical Research Letters
Volume23
Issue number10
DOIs
StatePublished - Jan 1 1996

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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    Zandt, G., Beck, S. L., Ruppert, S. R., Ammon, C. J., Rock, D., Minaya, E., Wallace, T. C., & Silver, P. G. (1996). Anomalous Crust of the Bolivian Altiplano, Central Andes: Constraints from Broadband Regional Seismic Waveforms. Geophysical Research Letters, 23(10), 1159-1162. [96GL00967]. https://doi.org/10.1029/96GL00967