Estimate of the Rigidity of Eclogite in the Lower Mantle From Waveform Modeling of Broadband S-to-P Wave Conversions

Samuel M. Haugland, Jeroen Ritsema, Satoshi Kaneshima, Michael S. Thorne

研究成果: Contribution to journalArticle査読

8 被引用数 (Scopus)

抄録

Broadband USArray recordings of the 21 July 2007 western Brazil earthquake (Mw=6.0; depth = 633 km) include high-amplitude signals about 40 s, 75 s, and 100 s after the P wave arrival. They are consistent with S wave to P wave conversions in the mantle beneath northwestern South America. The signal at 100 s, denoted as S1750P, has the highest amplitude and is formed at 1,750 km depth based on slant-stacking and semblance analysis. Waveform modeling using axisymmetric, finite difference synthetics indicates that S1750P is generated by a 10 km thick heterogeneity, presumably a fragment of subducted mid-ocean ridge basalt in the lower mantle. The negative polarity of S1750P is a robust observation and constrains the shear velocity anomaly δVS of the heterogeneity to be negative. The amplitude of S1750P indicates that δVS is in the range from −1.6% to −12.4%. The large uncertainty in δVS is due to the large variability in the recorded S1750P amplitude and simplifications in the modeling of S1750P waveforms. The lower end of our estimate for δVS is consistent with ab initio calculations by Tsuchiya (2011), who estimated that δVS of eclogite at lower mantle pressure is between 0 and −2% due to shear softening from the poststishovite phase transition.

本文言語英語
ページ(範囲)11,778-11,784
ジャーナルGeophysical Research Letters
44
23
DOI
出版ステータス出版済み - 12 16 2017

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

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