50-60 Pct Chance of Huge Quake Predicted in Western Japan

Tokyo, Aug. 28 (Jiji Press)–Active faults in and around the Kinki western Japan region could trigger an earthquake with a magnitude of 6.8 or larger with a 50-60 pct probability within the next 30 years, a government panel said Friday. The probability stood at 30 pct for active faults in the northwestern part of the region, 40-60 pct for those in the central part called the Kinki triangle and 7 pct for those in the Kii Peninsula, according to the government’s Earthquake Research Committee. The assessment is based on a total of 45 active faults in and around the Kinki region. The committee has already disclosed its long-term assessments for 114 major active faults across the country and in the Kyushu southwestern, Kanto eastern, Chugoku and Shikoku western regions. Its long-term assessments will be released later for the Chubu central, Tohoku northeastern and Hokkaido northern regions. The Kinki region has many active faults mainly because of the impact of the expansion of the Sea of Japan during the formation of the Japanese islands. The chance of a major earthquake in the region is as high as that of the Kanto region. Of the 45 active faults in the Kinki region, the highest magnitude of around 8.1 to 8.3 is predicted for the Yanagase-Sekigahara fault zone stretching from Fukui Prefecture to the border between Gifu and Shiga prefectures if three sections in the zone move simultaneously. If four sections become active together in the Median Tectonic Line fault zone near the border between the Kinki triangle and the Kii Peninsula, an earthquake with a magnitude of at least 8.0 could occur, according to the committee. An earthquake with a magnitude of around 8.0 is forecast to occur if the two main sections of the Yamasaki fault zone covering Okayama and Hyogo prefectures are active at the same time. Faults are categorized into S, A, Z and X ranks if the probability of an earthquake occurring within the next 30 years is 3 pct or more, 0.1-3 pct, less than 0.1 pct and unknown due to lack of data, respectively. Currently, nine faults are classified in the S rank. Of the two sections in the Rokko-Awaji Island fault zone in Hyogo Prefecture, the west coast section of Awaji Island, which caused the 1995 Great Hanshin Earthquake with a magnitude of 7.3, remains in the Z rank. The section between the southern edge of Mt. Rokko and the eastern coast of Awaji Island was reclassified from A to S. In the Yoro-Kuwana-Yokkaichi fault zone near northern Mie Prefecture, with an estimated magnitude of 7.4 to 7.8 during simultaneous activity in four sections, the rank for the northern and central parts, where the average activity interval was shortened, was raised from A to S. Conversely, the most recent estimated activity time for the main part of the Uemachi fault zone in Osaka Prefecture, with an estimated magnitude of 7.6 during activity, was renewed, and its rank was lowered from S to Z. The rank of the southern part of the Kyoto basin-Nara basin fault zone was maintained at S. The distribution of seismic intensity for predicted activity on each fault and fault zone was compiled by the secretariat of the Headquarters for Earthquake Research Promotion and was also released Friday. Kazushige Obara, chairman of the committee and emeritus professor at the University of Tokyo, said he hopes that the newly released data will be reflected in local governments’ damage estimates and hazard maps and used for disaster prevention. “There are concerns about Nankai Trough (major) earthquakes in the Kinki region, but we want people to be fully aware that there are many active faults under their feet and prepare for them,” he added. END [Copyright The Jiji Press, Ltd.]