Japan Institute Warns of Megaquakes after Aomori Temblor

Tokyo, Dec. 11 (Jiji Press)–A series of earthquakes with magnitudes of 7 or 8 may occur after a 7.5-magnitude quake struck off the east coast of Aomori Prefecture, part of Japan’s Tohoku northeastern region, on Monday, a research institute has said. Fumiaki Tomita, associate professor at the International Research Institute of Disaster Science of Japan’s Tohoku University, called on people to remain prepared for possible major quakes and tsunamis even after the Japan Meteorological Agency’s ongoing warning for a possible subsequent huge earthquake, which was issued soon after the Monday quake, ends at midnight next Monday. The warning was issued for residents of the Pacific coastal areas from Hokkaido, northernmost Japan, to Chiba Prefecture, east of Tokyo. Monday’s quake registered up to upper 6, the second-strongest level on Japan’s seismic intensity scale. According to the institute, quakes with magnitudes of 7 or 8 may strike south of the focus of Monday’s quake, or in other words north off Iwate Prefecture, which is part of Tohoku and south of Aomori. In the Pacific area off the coast of Tohoku, the ocean plate continues sinking into the land-side plate at the Japan Trench. As strain from the sinking accumulates at the boundary of the plates, part of the boundary area sometimes slips suddenly, causing megaquakes and tsunamis. According to the Japanese government’s earthquake research committee, Monday’s quake happened in the northern part of the focus area of the 1968 earthquake, which had a magnitude of 7.9 and killed 52 people. In the area north off Iwate, or the southern part of the focus area of the 1968 temblor, a powerful quake with a magnitude of 7.6 occurred in 1994, leaving three people dead. But no quakes with magnitudes of 7 or higher have happened there since then. Meanwhile, a 6.9-magnitude temblor occurred south of the northern area off Iwate on Nov. 9 this year. A tsunami advisory was issued at the time, and a 16-centimeter tsunami was observed in the city of Ofunato in the prefecture. After the Nov. 9 and Monday quakes, the northern part off Iwate remains the only area without major quakes, according to Tomita. “Earthquakes with magnitudes of 8 could strike the area (if large-scale slips occur between the two plates),” he warned. Monday’s quake caused tsunami waves, with the highest one, which measured 70 centimeters, observed at a port in Kuji. Tsunamis tend to be large at the port due to submarine topography around the facility. The highest of the tsunamis observed in Japan after the megaquake that occurred off Russia’s Kamchatka Peninsula on July 30 this year was seen at the Kuji port, measuring 141 centimeters. Shunichi Koshimura, professor at the institute, said that the 70-centimeter tsunami observed at the Kuji port after Monday’s quake was the fifth wave, which came about 90 minutes after the first wave reached the port. For future tsunamis, Koshimura warned, “We have to be careful about the biggest wave, which may come late.” “It was lucky that the highest tsunami in the Monday quake came at low tide,” which means that the tide level is 1.5 meters lower than at high tide,” he said. END [Copyright The Jiji Press, Ltd.]