Hokkaido Nansei-oki, Japan Earthquake of July 12, 1993

Keywords: Hokkaido, Nansei-oki, Japan Earthquake, July 12, 1993, Postearthquake Investigations, Strong Ground Motion, Tsunamis, Fires, Structural Damage, Liquefaction, Ground Failure, Lifelines, Highways, Tunnels, Transportation Systems, Port Failures, and Earthquake Engineering.

Abstract: This report reviews damages caused by the magnitude 7.8 earthquake which occurred offshore, southwest of the Island of Hokkaido in Northern Japan on July 12, 1993. The earthquake caused moderately strong ground shaking over a wide area. A peak ground acceleration of 0.50g was recorded about 100 km from the edge of the offshore aftershock zone. The shock was followed by a large tsunami, which caused water run-ups of up to 30.5 m and extensive shoreline damage on the Island of Okushiri and along the southwest coast of Hokkaido. The tsunami devastated the town of Aonae, on the southern tip of Okushiri Island. The tsunami was followed by a fire, which destroyed much of the town of Aonae. The earthquake shaking caused light to moderate damage to structures on Okushiri Island, light to moderate damage to infrastructure and industrial facilities, and extensive damage to roads and ports from ground failures up to about 100 km from the edge of the aftershock area. The primary lesson of the earthquake is that the triple hazards of earthquake shaking followed by tsunamis and uncontrolled fires can be devastating to modern cities.