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Fig. 6.8 Segment of shore 15 km south-west of the northern end of island Sumatra. The tsunami
height amounted to 15-20 m, here, while the heights of individual run-ups were up to 35 m above
the sea level. In this region the tsunami exerted a strong erosive and abrasive influence on the shore
and the nearby hills. In the background of the photograph one can see an abrasion niche, formed
after the tsunami. The distance from the shoreline is 300 m (Photo by T. K. Pinegina) (see also
Plate 11 in the Colour Plate Section on page 319)
a whole number of historical tsunamis in various regions over the world has shown
that tsunamis do not form new shapes of the coastal relief (for instance, like new
swells), but are capable of very strongly washing away the existing shapes. The
width of the zone subjected to erosive activity depends, first of all, on the tsunami
intensity and on the flow velocity. Thus, for example, in the Aceh province, in
the North of Sumatra, the width of the 'erosion' zone of the December 26, 2004,
earthquake impact amounted to 2-3 km and, farther, at a distance of 5-10 km was
the zone of accumulation of tsunamigenic material.
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