Geoscience Reference
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Fig. 5.10 Global chart showing energy propagation of the 2004 Sumatra tsunami calculated from
MOST. Filled colors show maximum computed tsunami heights during 44 hours of wave prop-
agation simulation. Contours show computed arrival time of tsunami waves. Circles denote the
locations and amplitudes of tsunami waves in three range categories for selected tide-gauge sta-
tions. Inset shows fault geometry of the model source and close-up of the computed wave heights
in the Bay of Bengal. Distribution of the slip among four subfaults (from south to north: 21 m,
13 m, 17 m, 2 m) provides best fit for satellite altimetry data and correlates well with seismic
and geodetic data inversions (see also Plate 6 in the Colour Plate Section on page 314) (Reprinted
from [Titov et al. (2005)] by permission of the publisher)
coastal measurements at one's disposal. Since the tsunami dynamics in the open
ocean is linear, the height of a wave is proportional to the square root of its en-
ergy. Thus, the space distribution of calculated maximum wave heights, presented
in Fig. 5.10, provides a clear picture of tsunami energy propagation. Numerous ver-
sions of calculations, performed for different values of bottom deformations, sizes
and orientations of the source, have revealed that all these parameters insignificantly
influence wave propagation in the remote zone. We right away note that in the close
zone the shape and orientation of the source happen to be decisive parameters.
A very important fact, testifying in favour of the numerical model being adequate,
is the good agreement between wave amplitudes, resulting from calculations, and
those registered by coastal stations. Thus, for example, the anomalously high values
of amplitudes in the remote zone reflect precisely the main directions of wave energy
propagation. The coastal stations in Halifax (Canada), Manzanillo (Mexico), Callao
(Peru), Arice (Chile) recorded wave heights exceeding 50 cm. Being at a significant
distance from the source (over 20,000 km), each of the sites indicated is to be found
in an area, related to the end of one of the 'wave rays'.
Numerical calculations, corroborated by in situ data, confirm the assumptions
that two main factors influence tsunami propagation: the source configuration (ge-
ometry) and the wave-guide properties of mid-oceanic ridges. We recall that the con-
tinental shelf can also serve as a wave guide. In many cases waves, captured by
the shelf, are the cause of prolonged oscillations of the water level at the coast.
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