60
It may take at least several 10 years to recover
the coseismic land subsidence. What creatures
will advance to new environment and will
disappear? We have to clarify not only short-term
effect which may explain an initial recovery of
intertidal and subtidal animals but also a longterm effect which may explain continuous
changes in population with land subsidence.
4
Effects of Man-Made
Structures
Almost all tidal fl ats in Mangoku-ura Inlet have
lost as a result of land subsidence after the earthquake. The mountain sediment has been putting
into sea from October 2013 to construct artifi cial
tidal fl ats for Manila clam culture (Fig. 6 ). Silt is
included in a certain percentage of the mountain
sediment, turbidity sometimes occurred in the sea
when low pressure came. We need to clarify
whether or not there is a new recruitment of juvenile after the summer 2014.
The magnitude 7.7 earthquake occurred in
1993 in the Sea of Japan near the Okushiri Island
in southwest-off Hokkaido, northern Japan
(Satake and Tanioka 1995 ). The tsunami reached
several minutes after the earthquake. The tsunami was 32 m high in maximum. The whole
island subsided by 5–80 cm. The tsunami inundated large parts of urban area in Okushiri Island
especially in Aonae area, despite its artifi cial wall
of tsunami defenses. The destructive power of
this tsunami led to an overhaul of the sea defenses
Fig. 6 (a and b ) Artifi cial tidal fl ats made by mountain sediment in Mangoku-ura Inlet; ( c ) Turbidity occurs when stir
the newly-introduced mountain sediment
K. Okoshi
It may take at least several 10 years to recover
the coseismic land subsidence. What creatures
will advance to new environment and will
disappear? We have to clarify not only short-term
effect which may explain an initial recovery of
intertidal and subtidal animals but also a longterm effect which may explain continuous
changes in population with land subsidence.
4
Effects of Man-Made
Structures
Almost all tidal fl ats in Mangoku-ura Inlet have
lost as a result of land subsidence after the earthquake. The mountain sediment has been putting
into sea from October 2013 to construct artifi cial
tidal fl ats for Manila clam culture (Fig. 6 ). Silt is
included in a certain percentage of the mountain
sediment, turbidity sometimes occurred in the sea
when low pressure came. We need to clarify
whether or not there is a new recruitment of juvenile after the summer 2014.
The magnitude 7.7 earthquake occurred in
1993 in the Sea of Japan near the Okushiri Island
in southwest-off Hokkaido, northern Japan
(Satake and Tanioka 1995 ). The tsunami reached
several minutes after the earthquake. The tsunami was 32 m high in maximum. The whole
island subsided by 5–80 cm. The tsunami inundated large parts of urban area in Okushiri Island
especially in Aonae area, despite its artifi cial wall
of tsunami defenses. The destructive power of
this tsunami led to an overhaul of the sea defenses
Fig. 6 (a and b ) Artifi cial tidal fl ats made by mountain sediment in Mangoku-ura Inlet; ( c ) Turbidity occurs when stir
the newly-introduced mountain sediment
K. Okoshi