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

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

Research output: Contribution to journalArticle

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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)
Pages (from-to)1159-1162
Number of pages4
JournalGeophysical Research Letters
Volume23
Issue number10
StatePublished - 1996

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Poisson ratio
crusts
waveforms
earthquakes
crust
broadband
earthquake
seismographs
crustal thickness
seismograph
crustal structure
Earth mantle
quartz
mantle
estimates
thickening

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Anomalous Crust of the Bolivian Altiplano, Central Andes : Constraints from Broadband Regional Seismic Waveforms. / Zandt, George; Beck, Susan; Ruppert, S. R.; Ammon, C. J.; Rock, D.; Minaya, E.; Wallace, T. C.; Silver, P. G.

In: Geophysical Research Letters, Vol. 23, No. 10, 1996, p. 1159-1162.

Research output: Contribution to journalArticle

Zandt, G, Beck, S, Ruppert, SR, Ammon, CJ, Rock, D, Minaya, E, Wallace, TC & Silver, PG 1996, 'Anomalous Crust of the Bolivian Altiplano, Central Andes: Constraints from Broadband Regional Seismic Waveforms', Geophysical Research Letters, vol. 23, no. 10, pp. 1159-1162.
Zandt, George ; Beck, Susan ; Ruppert, S. R. ; Ammon, C. J. ; Rock, D. ; Minaya, E. ; Wallace, T. C. ; Silver, P. G. / Anomalous Crust of the Bolivian Altiplano, Central Andes : Constraints from Broadband Regional Seismic Waveforms. In: Geophysical Research Letters. 1996 ; Vol. 23, No. 10. pp. 1159-1162.
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