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Hokkaido Nansei-Oki Tsunami, July 12, 1993 |
An earthquake occurred off the west coast of Hokkaido and the small offshore
island of Okushiri in the Sea of Japan. In two to five minutes the tsunami, one of
the largest in Japan's history, engulfed the coastline of Okushiri Island and the
central west coast of Hokkaido. Almost two hundred fatalities were associated with
the event, with more than half attributed to the tsunami. The $600 million in property
losses were attributed primarily to the tsunami. This tsunami caused spectacular localized
damage, especially on the southwestern shores of Hokkaido and on Okushiri Island.
This slide set shows damage to ships, dwellings, and businesses, and unique views
of clocks stopped in time by the tsunami.On July 12, 1993, at 22:17 local time (13:17
GMT), a magnitude 7.8 earthquake occurred off the west coast of Hokkaido and the small
offshore island of Okushiri in the Sea of Japan (42' 47'N, 139' 12'W). In two to five
minutes the tsunami engulfed the coastline of Okushiri Island and the central west
coast of Hokkaido. Almost two hundred fatalities were associated with the event, with
more than half attributed to the tsunami. The death toll on Okushiri Island was 165.
The $600 million in property losses were attributed primarily to the tsunami. This
1993 earthquake filled a previously identified seismic gap. This tsunami caused spectacular
localized damage, especially on the southwestern shores of Hokkaido and on Okushiri
Island.West Coast of Okushiri Island: This area experienced the highest runup measurements.
All twelve houses in the village of Monai were destroyed, killing 10 persons. Runup
measurements around the village were 20 m and in a small valley north of Monai on
the southwest coast the runup was measured at 31 m, the maximum for this event. South
of Monai, tsunami runups along the coast ranged from 15 to 20 m. Vegetation was stripped
off the hillside, and large boulders up to one-meter in diameter were deposited on
the flooded vegetation. These data suggest that the initial wave arrived from west
of Okushiri Island.Southern Coast of Okushiri Island: The tsunami was refracted by
the shoaling bathymetry at both ends of the island. The town of Aonae (population
1,600) at the southern tip of Okushiri was hardest hit.About four to five minutes
after the main earthquake shock, the first tsunami wave arrived, flooding the southern
tip of the island and the entire first row of houses nearest the coast. Two fires
started on the damaged fishing vessels after this first wave. The tsunami appeared
to arrive from the northeast, with flooding of between three and seven meters throughout
the town.About seven minutes after the first wave, a second, larger wave hit from
the east carrying the burning boats into the main town. The second wave advanced further
ashore than the first and completely flooded the first three rows of houses with a
runup of between five and ten meters throughout the town.The combination of a strong,
northeast wind, the burning boats, and an ample supply of heating propane and kerosene
spread the fire quickly and destroyed 340 homes. However, only two of the 114 deaths
in Aonae were caused by fire. The houses in the central part of Aonae were flooded
by tsunami waves that ran up to a height of five meters. Further from the shore the
structures were destroyed by fire. The tsunami destroyed a portion of the sea wall,
and fishing boats were left "high and dry" in the inundation zone.Northern and Eastern
Coasts of Okushiri: At Inaho, on the northern point of Okushiri Island, 13 people
were killed and all houses were destroyed by the 10-m waves. The eastern side of Okushiri
Island appeared to be sheltered from the waves, and the measured tsunami runup was
between two and five meters.Hokkaido: Severe damage was caused by the earthquake and
accompanying fires, landslides, and the tsunami on southwestern Hokkaido-540 houses
were destroyed and 1,834 others were damaged. The tsunami also hit the Island of Hokkaido,
arriving at Ota Bay within five minutes of the main shock and destroying five homes.
Runup in this area was nine meters. Damage also occurred at Setana from the six meter
waves. The coastline from Suttsu to south of Ota Bay was hardest hit with runup values
of five to nine meters. Outside this area, the tsunami intensity tapered off rapidly,
and runup values were below five meters.Other Areas: After 90 minutes, the tsunami
struck the coast of the Republic of Korea, where a maximum tsunami runup of two meters
was recorded. One person on a fishing boat was killed near Aomori, Honshu. A runup
of nearly one meter was recorded there. Three people from the southeast coast of Russia
were missing after the tsunami. The tsunami affected much of the southeastern coast
of Russia and also caused damage to a factory at Kamenka, Sakhalin Island.The tsunami
traveled to Russia within 30 minutes, causing runups of one to four meters. Damage
estimates were over $6 million (U.S. Dollars). Approximately 700 fishing boats were
damaged or lost off western Japan, southeastern Russia, the Republic of Korea, and
the Democratic People's Republic of Korea.
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