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A single Rayleigh mode may exist with multiple values of phase-velocity at one frequency

Forbriger, Thomas; Gao, Lingli; Malischewsky, Peter; Ohrnberger, Matthias; Pan, Yudi

Abstract (englisch):
Other than commonly assumed in seismology, the phase velocity of Rayleigh waves is not
necessarily a single-valued function of frequency. In fact, a single Rayleigh mode can exist
with three different values of phase velocity at one frequency. We demonstrate this for the first
higher mode on a realistic shallow seismic structure of a homogeneous layer of unconsolidated
sediments on top of a half-space of solid rock (LOH). In the case of LOH a significant
contrast to the half-space is required to produce the phenomenon. In a simpler structure
of a homogeneous layer with fixed (rigid) bottom (LFB) the phenomenon exists for values
of Poisson’s ratio between 0.19 and 0.5 and is most pronounced for P-wave velocity being
three times S-wave velocity (Poisson’s ratio of 0.4375). A pavement-like structure (PAV)
of two layers on top of a half-space produces the multivaluedness for the fundamental mode.
Programs for the computation of synthetic dispersion curves are prone to trouble in such cases.
Many of them use mode-follower algorithms which loose track of the dispersion curve and
miss the multivalued section. We show results for well established programs. ... mehr

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Postprint §
DOI: 10.5445/IR/1000119814/post
Frei zugänglich ab 18.03.2021
Zugehörige Institution(en) am KIT Geophysikalisches Institut (GPI)
Institut für Angewandte und Numerische Mathematik (IANM)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 0956-540X, 1365-246X
KITopen-ID: 1000119814
Erschienen in Geophysical journal international
Band 222
Heft 1
Seiten 582-594
Projektinformation DFG, DFG EIN, FO 506/1-1
Vorab online veröffentlicht am 17.03.2020
Nachgewiesen in Web of Science
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