A tsunami following a M8.1 earthquake caused serious
April 2007 in UTC. The tsunami destroyed some coastal
villages and killed 52 people according to the report of the
government of the Solomon Islands on 30 April 2007. A
post tsunami field survey was conducted in Simbo Island,
New Georgia Island near the epicenter for understanding
of tsunami damages and characteristics of the striking
tsunami.
In the field survey, tsunami inundation heights and runup
heights were measured from the level of sea surface at
time of each measurement, and were converted to the
heights above the estimated level of sea surface at the
time, the number of tsunami waves, scene of tsunami
striking and people’s activity when the tsunami struck
were gathered from residents and others.
Figure 1 indicates tsunami inundation and runup heights
measured in the field survey. The highest runup in our
survey is 9.0 m in Tapurai, Simbo Island, which is in the
subsidence area by the earthquake (Fritz and Kalligeris,
5 m at the north part of Simbo Island and at the south
coast of Ghizo Island, which suffer severe damages. On
the contrary, tsunami inundation heights of 2 m or less
are at the east coast of the south part of Vella Lavella
and at the north coast of the east part of Ghizo Island
which locates on the back side of the island against the
tsunami incident direction.
Numerical simulations are carried out and compared to
the survey results. The bathymetric data is based on 1-
minute grid data of GEBCO and a nautical chart around
Ghizo Island. The minimum grid size of calculation is 200
numerical simulations based on several fault models,
Tanioka’s model is finally selected, which is determined
from the results of ground uplift and subsidence by the
earthquake.
In the numerical simulations, the tsunami is trapped
around the islands near the epicenter and hardly
propagated behind the islands. Especially the high
tsunami appears around overall of Simbo Island and the
inundation and runup heights measured in the field
good agreement with the survey results in the locations
where there are less developing coral reefs in front of
coasts. However, in Munda, Vonunu, Titiana and New
Manra, the numerical results are larger than the survey
places but no or narrow reefs are in the calculation.
MITIGATION OF TSUNAMI DISASTERS
Human lives were saved by evacuation to hills near
looked at the tsunami coming in the offshore. High-floored
houses with stilts also saved human lives as well as
reduce tsunami destruction rate in the area. These facts
indicate importance of vertical evacuation.
Figure 1 - Measured tsunami inundation and runup
heights ( : Inundation height, : Runup height)
heights and calculated tsunami heights
Fritz and Kalligeris (2008): Ancestral heritage saves tribes
during 1 April 2007 Solomon Islands tsunami, GRS, 35.