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involving the construction of higher tsunami
seawalls. Huge seawalls break the continuity of
nature to land from the sea (Fig. 7 ). Twenty years
after the Okushiri earthquake, the construction of
tsunami seawalls has begun in the Pacifi c coast of
Tohoku district without environmental assessment. The height of the tsunami seawalls will be
exceeding 14 m in maximum.
References
Abe H, Sugeno Y, Chigama A (1990) Estimation of the
height of the Sanriku Jogan 11 Earthquake-Tsunami
(A.D. 869) in the Sendai Plain. Zishin 43:513–525
(in Japanese with English abstract)
Dawson S, Smith DE, Ruffman A, Shi S (1996) The diatom biostratigraphy of tsunami sediments: examples
from recent and middle holocene events. Phys Chem
Earth 21:87–92
Fig. 7 Coastline of
Okushiri Island, Hokkaido
Japan. ( a ) Natural coast.
Coastal vegetation is
continuous until the beach.
( b ) Coast which are
divided by the tsunami
seawalls with some
vegetation on the shore.
( c ) Huge seawalls. There is
no vegetation at all on
the shore
Impact of Repeating Massive Earthquakes on Intertidal Mollusk Community in Japan