Japan Tsunami, 1993

The Hokkaido Nansei-Oki Tsunami, July 12, 1993

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 degrees 47'N, 139 degrees 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, thirteen people were killed and all houses were destroyed by the ten- meter 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. Five hundred forty 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 ninety 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 off Aomori, Honshu, and a runup of nearly one meter was recorded at Aomari, Honshu. 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 thirty minutes, causing runups of one to four meters. Damage estimates were over US $6 million. Approximately 700 fishing boats were damaged or lost off western Japan, southeastern Russia, and the Republic of Korea, and the People's Republic of Korea.

	Tsunami and fire damage SE Okushiri Is. A view of tsunami and related fire damage on southeast Okushiri Island in the community of Aonae. Photo orientation is looking northeast. Numerous fires broke out following the tsunami, adding to the property loss and misery. More than 120 people were killed in Japan (Okushiri and Hokkaido Islands) by the tsunami. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Tsunami damage at Aonae, Okushiri Is. Aonae, Okushiri Island looking southeast. Structures in the foreground were damaged by fires fueled by above-ground kerosene and propane tanks following the tsunami. The concrete steps provided a means of escape for some residents following the strong earthquake. The steps were originally installed for residents to easily walk between the housing area on the bluff (not visible) and the community area near the sea. Many residents remembered the May, 1983, earthquake and tsunami and used this previous experience to escape the deadly tsunami waves in 1993, using the steps as the fastest way to safety. Without this previous knowledge, the casualty count would probably have been much higher. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Clock at Aonae showing arrival time of wave Numerous battery-operated clocks were found scattered in the debris. These provide a rough estimate of the arrival time of inundating, destructive waves. The salt water shorted the electrical mechanism in the clock, causing it to stop. This clock at Aonae, Okushiri Island, shows a travel time (not necessarily for the first wave-but the first inundating wave at this specific location in Aonae) of some fifteen minutes following the earthquake. Clocks on the west side of Okushiri Island showed travel times of as little as six to seven minutes. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Scattered debris at Aonae, Okushiri Is. Debris scattered by the tsunami at Aonae, Okushiri Island. Most of the homes on Okushiri are framed in wood and the debris trail largely consisted of wood, roofing materials, and personal effects scattered randomly about the inundation area. The clock in the foreground shows a damaging tsunami wave travel time of eight minutes. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Beached fishing boat at Aonae, Okushiri Is. Aonae, Okushiri Island. Fishing boat (configured for catching squid) is beached high and dry near a damaged fire truck. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	View to north of damage to prosperous tourist area at Aonae, Okushiri Is. Aonae, Okushiri Island, looking north. Note red/white lighthouse is leaning to the northeast. Damage to the lighthouse was caused by the earthquake and not the tsunami. Debris in the foreground is all that remains of a prosperous tourist area occupied by small shops, houses, and kiosks. Concrete foundations and pads, wiped clear of houses and other structures, can be seen in the debris. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	View to south of above area Aonae, Okushiri Island, looking south An obelisk in the distance survived the damaging tsunami waves that rose to a height of five to ten meters at Aonae. Note how the waves undercut the concrete pad in the foreground. No wood-framed structure survived the tsunami waves in this immediate area. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Debris scattered near harbor at Aonae, Okushiri Is. Note the plastic containers and other debris scattered near the harbor at Aonae. Many of the personal and business effects show that Aonae was a prosperous tourist community with a well established squid and sea urchin fishery. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	High water mark of five meters shown on side of damaged house Aonae, Okushiri Island. High water marks are clearly evident on the side of this partially damaged house. Runup in this area was measured at five meters. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Small fishing boats deposited near harbor at Aonae Numerous small and large fishing boats were scattered by the tsunami waves and deposited in a variety of places. Near the harbor at Aonae, these boats were forcefully thrust into a seafood processing plant. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Clock half burried in sand shows travel time of twenty minutes Revealing a tsunami wave travel time of twenty minutes, this clock was found half buried in sand and other debris deposited by the tsunami at Aonae. Note that the small reinforced concrete building in the background survived the damaging tsunami waves. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Large barge that was moved 75 m by waves A large seventy-meter-long barge was moved seventy-five meters from the harbor by the flooding tsunami waves. The crane on the barge is used to lift concrete dolos from the nearby fabricating area to breakwaters and protective bulkheads surrounding the harbor area. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Fishing boat deposited on concrete shore protection barrier, Aonae A fishing boat was deposited on top of a concrete shore protection barrier at Aonae. Note wood debris from houses and other structures scattered about the area. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	A small valley on the west side of Okushiri Is. On the west side of Okushiri Island many locations experienced a maximum runup exceeding 20 m. This small valley leading to the ocean experienced a spectacular runup of 31 m. Note the debris in the foreground, including a broken steel reinforced concrete utility pole. Discolored and dead plants and grasses are evident on the hillside. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Damage at Monai, west Okushiri Is. The village of Monai, west Okushiri Island. Except for a few houses on the bluff (not visible) the community was completely destroyed by the tsunami waves. The waves reached an elevation of nearly twenty meters above sea level, flooding three hundred meters inland. Ten persons were killed and twelve houses were destroyed. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Debris Line at Monai, West Okushiri Is. The village of Monai, west Okushiri Island. The leading edge of the debris line marks the extent of the flooding. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Debris on highway overpass near Monai, Okushiri Is. Highway overpass near Monai. Note the debris, including a corrugated sheet metal panel, wrapped around the guard rail. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Debris in overhead utility wires on west Okushiri Is. West coast of Okushiri Island. The tsunami waves deposited debris from the hillside in the overhead utility wires; note the discoloration of plants and grasses. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Vegetation stripped from hillside, west Okushiri Is. West coast of Okushiri Island. The tsunami stripped plants and grasses from the hillside leaving debris in the overhead utility wires. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]
	Waves overtopped roadway, west Okushiri Is. West coast of Okushiri Island. The Sea of Japan, to the right, in this area has a tidal range of less than 0.5 m. Note how the tsunami waves crossed the roadway, splashed onto the hillside and killed/discolored the native plants and grasses. In this area, the tsunami reached a height of about 10 meters above sea level. [Photo Credit: Dennis J. Sigrist, International Tsunami Information Center, Honolulu, Hawaii]