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

Satoshi Kaneshima, Masataka Ando, Shozou Kimura

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41 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 - 1988
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General

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