Shear wave splitting and mantle flow beneath LA RISTRA

Rengin Gök, James F. Ni, Michael West, Eric Sandvol, David Wilson, Richard Aster, W. Scott Baldridge, Stephen Grand, Wei Gao, Frederik Tillmann, Steve Semken

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Shear-wave splitting parameters (fast polarization direction and delay time) are determined using data from LA RISTRA (Colorado pLAteau RIo Grande Rift/Great Plains Seismic TRAnsect), a deployment of broadband seismometers extending from the Great Plains, across the Rio Grande Rift and the Jemez Lineament, to the Colorado Plateau. Results show that the fast polarization directions are sub-parallel to North American absolute plate motion. The largest deviations from the plate motion are observed within the western edge of the Great Plains and in the interior of the Colorado Plateau where lithospheric anisotropy may be significant. Delay times range from 0.8 to 1.8 seconds with an average value of 1.4 seconds; the largest values are along the Jemez Lineament and the Rio Grande Rift which are underlain by an uppermost mantle low velocity zone extending to depths of ∼200 km. The anisotropy beneath the central part of LA RISTRA shows a remarkably consistent pattern with a mean fast direction of 40° ± 6°. Seismic anisotropy can be explained by differential horizontal motion between the North American lithosphere and westerly to southwesterly flow of the asthenospheric mantle. The approximately N-S fast direction found beneath western Texas is similar to that observed beneath the southern rift and may reflect a different dynamic regime.

Original languageEnglish (US)
Pages (from-to)16-1 - 16-4
JournalGeophysical Research Letters
Issue number12
StatePublished - Jun 15 2003
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)


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