A single Rayleigh mode may exist with multiple values of phase-velocity at one frequency
Forbriger, Thomas
1; Gao, Lingli 2; Malischewsky, Peter; Ohrnberger, Matthias; Pan, Yudi 1
1 Geophysikalisches Institut (GPI), Karlsruher Institut für Technologie (KIT)
2 Institut für Angewandte und Numerische Mathematik (IANM), Karlsruher Institut für Technologie (KIT)
1; Gao, Lingli 2; Malischewsky, Peter; Ohrnberger, Matthias; Pan, Yudi 11 Geophysikalisches Institut (GPI), Karlsruher Institut für Technologie (KIT)
2 Institut für Angewandte und Numerische Mathematik (IANM), Karlsruher Institut für Technologie (KIT)
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
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
| Zugehörige Institution(en) am KIT | Geophysikalisches Institut (GPI) Institut für Angewandte und Numerische Mathematik (IANM) KIT-Zentrum Klima und Umwelt (ZKU) |
| Publikationstyp | Zeitschriftenaufsatz |
| Publikationsjahr | 2020 |
| Sprache | Englisch |
| Identifikator | ISSN: 0956-540X, 1365-246X KITopen-ID: 1000119814 |
| Erschienen in | Geophysical journal international |
| Verlag | Oxford University Press (OUP) |
| Band | 222 |
| Heft | 1 |
| Seiten | 582-594 |
| Projektinformation | DFG, DFG EIN, FO 506/1-1 |
| Vorab online veröffentlicht am | 17.03.2020 |
| Nachgewiesen in | Dimensions Web of Science |