Evidence from shear-wave splitting for the restriction of seismic anisotropy to the upper crust

Satoshi Kaneshima, Masataka Ando, Shozou Kimura

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

The existence of anistropy in the propagation speed of seismic waves through the Earth's crust has been attributed to the non-random alignment of microcracks in the crust1. For sparsely distributed, parallel vertical cracks, perturbation theory predicts the splitting of a shear wave into two orthogonally polarized waves2-4. Here we present extremely clear evidence for shear-wave splitting in three-component seismograms from crustal and sub-crustal microearthquakes recorded in the Shikoku district of Japan. Quantitative analysis of travel-time differences between split shear waves leads to the conclusion that the observed anisotropy is limited to the upper crust, shallower than 10-15 km. This model is consistent with recent results from reflection seismology5, and implies that microcrack density or orientation changes from the upper to the lower crust.

Original languageEnglish
Pages (from-to)627-629
Number of pages3
JournalNature
Volume335
Issue number6191
DOIs
Publication statusPublished - Jan 1 1988
Externally publishedYes

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seismic anisotropy
wave splitting
upper crust
S-wave
microcrack
microearthquake
seismogram
seismic wave
quantitative analysis
travel time
lower crust
crack
anisotropy
perturbation

All Science Journal Classification (ASJC) codes

  • General

Cite this

Evidence from shear-wave splitting for the restriction of seismic anisotropy to the upper crust. / Kaneshima, Satoshi; Ando, Masataka; Kimura, Shozou.

In: Nature, Vol. 335, No. 6191, 01.01.1988, p. 627-629.

Research output: Contribution to journalArticle

Kaneshima, Satoshi ; Ando, Masataka ; Kimura, Shozou. / Evidence from shear-wave splitting for the restriction of seismic anisotropy to the upper crust. In: Nature. 1988 ; Vol. 335, No. 6191. pp. 627-629.
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