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| Titel |
Tsunami excitation by inland/coastal earthquakes: the Green function approach |
| VerfasserIn |
T. B. Yanovskaya, F. Romanelli, G. F. Panza |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 3, no. 5 ; Nr. 3, no. 5, S.353-365 |
| Datensatznummer |
250001234
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| Publikation (Nr.) |
 copernicus.org/nhess-3-353-2003.pdf |
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| Zusammenfassung |
| In the framework of the linear theory,
the representation theorem is derived for an incompressible liquid layer
with a boundary of arbitrary shape and in a homogeneous gravity field. In
addition, the asymptotic representation for the Green function, in a layer
of constant thickness is obtained. The validity of the approach for the
calculation of the tsunami wavefield based on the Green function technique
is verified comparing the results with those obtained from the modal
theory, for a liquid layer of infinite horizontal dimensions. The Green
function approach is preferable for the estimation of the excitation
spectra, since in the case of an infinite liquid layer it leads to simple
analytical expressions. From this analysis it is easy to describe the
peculiarities of tsunami excitation by different sources. The method is
extended to the excitation of tsunami in a semiinfinite layer with a
sloping boundary. Numerical modelling of the tsunami wavefield, excited by
point sources at different distances from the coastline, shows that when
the source is located at a distance from the coastline equal or larger
than the source depth, the shore presence does not affect the excitation
of the tsunami. When the source is moved towards thecoastline, the low
frequency content in the excitation spectrum ecreases, while the high
frequencies content increases dramatically. The maximum of the excitation
spectra from inland sources, located at a distance from the shore like the
source depth, becomes less than 10% of that radiated if the same source is
located in the open ocean. The effect of the finiteness of the source is
also studied and the excitation spectrum is obtained by integration over
the fault area. Numerical modelling of the excitation spectra for
different source models shows that, for a given seismic moment, the
spectral level, as well as the maximum value of the spectra, decreases
with increasing fault size. When the sources are located in the vicinity
of a shore, the synthetic mareograms calculated at distances greater than
the source depth show that the maximum tsunami amplitude decays with
decreasing source-to-shore distance. The rate of decay is dependent on the
dip, length and depth of the fault. The tsunami intensity, defined as
maximum peak-to-peak amplitude, decays with the inland distance of the
source from the coast. At an inland distance equal to the source depth, it
becomes 4–5 times less than that from a source in the open ocean. If the
source is located under the coastline, the intensity of tsunami is
approximately the same as for oceanic sources. |
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