Geoscience Reference
In-Depth Information
The American gunship Wateree in the foreground and
the Peruvian warship America in the background. Both
ships were carried inland 3 km by a 21 m high tsunami
during the Arica, Peru (now Chile) event of 13 August
1868. Retreat of the sea from the coast preceded the
wave, bottoming both boats. The Wateree, being
flat-hulled, bottomed upright and then surfed the crest
of the tsunami wave. The America, being keel-shaped,
was rolled repeatedly by the tsunami (photograph
courtesy of the United States Geological Survey
Catalogue of Disasters #A68H08-002).
Fig. 10.15
the bay. Figure 10.15 dramatically illustrates the
potential extent of flooding inland that such tsunami
are able to generate. The American gunship
Wateree
and the Peruvian ship
America
were standing offshore
during the Arica, Chile, tsunami of 13 August 1868.
They were both swept 5 km up the coast, and 3 km
inland over the top of sand dunes by two successive
tsunami waves. The ships came to rest 60 m from a
vertical cliff at the foot of the coastal range, against
which the tsunami had surged to a height 14 m above
sea level. Unfortunately, 25 000 deaths also resulted
from this event along the coasts of Chile and Peru.
Run-up heights also depend upon the configuration
of the shore, diffraction, characteristics of the wave,
and resonance. Within some embayments, it takes
several waves to build up peak tsunami wave heights. If
the first wave in the tsunami wave train is the highest,
then it can be dampened out. Figure 10.16 maps the
heights of tsunami run-up around Hawaii for the 1946
Aleutian earthquake. The northern coastline facing the
tsunami advance received the highest run-up.
However, there was also a tendency for waves to wrap
around the islands and strike hardest at supposedly
protected sides, especially on the islands of Kauai and
Hawaii. Because of refraction effects, almost every
promontory also experienced high run-ups, often
Sequential photographs of the 9 March 1957 tsunami
overriding the backshore at Laie Point, Oahu, Hawaii. The
tsunami was generated by an earthquake with a surface
magnitude of 8.3 in the Aleutian Islands, 3600 km away.
Fifty-four people died in this tsunami (photograph credit:
Henry Helbush. Source: United States Geological Survey,
Catalogue of Disasters #B57C09-002).
Fig. 10.14
the largest run-up height recorded is that produced by
an earthquake-triggered rockfall into Lituya Bay,
Alaska, on 9 July 1958. The resulting wall of water
surged 524 m up the shoreline on the opposite side of
