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ID 13931
JaLCDOI
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Title Alternative
Inversion of normal mode frequencies for estimation of lateral heterogeneity of the earth's elasticity atructure: A numerical test
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Author
Onishi, Seiji
Abstract
An investigation was made on effect of lateral heterogenity of the earth's elasticity structure on the normal mode frequencies. The lateral heterogeneity is expressed by an expansion of spherical harmonic functions, Pιm(cosθ)sinmΦ and Pιm(cosθ)cosmΦ, up to the second order harmonics (ι≤2). Free oscillation freguencies of the heterogeneous earth were computed by the xyz algorithm. Further we derived an analytic expression of partial derivatives of eigenfrequency with respect to the expansion coefficients, and performed a numerical test to verify whether or not it is possible to estimate the heterogeneity of the earth's structure by the inversion of noemal mode frequencies. When the earth is assumed to be elastically isotropic spheroid with short polar and long equatorial radii, frequency spectra affected by longitudinal heterogeneity terms, Pιm(cosθ)(sinmΦ, cosmΦ) (m≠ 0), for given values of ι and m coincide with each other, because these two terms describe the same heterogeneity when the earth is rotated by π/2m around rotation axis. In such a case, we cannot determine accurately the expansion coefficients of tha two heterogeneity terms by inversion of normal mode frequencies, whereas the coefficients of the latitudinal heterogeneity Pι0(cosθ) can be precisely determined. Therefore it is difficult to estimate of lateral heterogeneity of the earth's elasticity structure by the inversion of normal mode frequencies.
Keywords
Normal Mode
Inversion
Earth's Structure
Lateral Heterogeneity
Publication Title
Okayama University Earth Science Report
Published Date
1996-09-20
Volume
volume3
Issue
issue1
Publisher
岡山大学理学部地球科学教室
Publisher Alternative
Department of Earth Sciences Faculty of Science, Okayama University
Start Page
33
End Page
42
ISSN
1340-7414
NCID
AN10506284
Content Type
Departmental Bulletin Paper
OAI-PMH Set
岡山大学
language
日本語
Copyright Holders
岡山大学地球科学研究報告編集委員会
File Version
publisher
NAID
Eprints Journal Name
esr