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[MIS15-05] Earthquakes and subsequent rock falls at the west of Yari-Hotaka range in the Northern Alps in September 2021
Keywords:earthquake swarm, talus, climbing trail, mountain hut, Tourism disaster prevention, the Japanese Alps
At 17:18 on September 19, 2021, an earthquake of magnitude 5.3 occurred under the northern Japanese Alpse. The epicenter of the earthquake was 10 km below the ground, 2 km northwest of Mt. Yarigatake. The seismographs in Kamioka-cho by the Japan Meteorological Agency (JMA), Kamitakara-mura by Kyoto University, and Yarigatake Sanso Hut by TV Matsumoto Cablevision recorded JMA seismic intensity 3, 4, and 5-, respectively. At the event of the earthquake, we happened to be at a tent site near Mt. Minami-dake (4 km south-southeast of the epicenter), and immediately after a momentary rumbling of the earth, we encountered a tremor to the extent that a stone barrier beside the tent collapsed. The next morning, we descended to Karasawa (a bottom of the Karasawa cirque) via Daikiretto (one of the most difficult trail on the ridge) and Kita-Hotaka Hut on the south side of Minami-dake. We saw fresh rock deposition along the trail, and We ourself was involved in a small rockfall accident. (One person has been killed by a rock fall after the earthquake. We sincerely pray for his soul.)
The earthquake occurred in the evening when most of the climbers had finished their activities, and no major accidents occurred except for the death of one person. However, earthquakes like this case have occurred repeatedly in the past in this range, such as the one in April 2020 (maximum M 5.5) and the one in August 1998 (M 5.6). In addition, this area has many steep and unstable rocky terrain, and popular mountain climbing routes are concentrated, so there have been many accidents involving falling rocks. Therefore, it is necessary to make special preparations for earthquakes and falling rocks unique to this region. In this paper, we report on the damage caused by the earthquake and how climbers and mountain huts responded afterwards.
The earthquake occurred in the evening when most of the climbers had finished their activities, and no major accidents occurred except for the death of one person. However, earthquakes like this case have occurred repeatedly in the past in this range, such as the one in April 2020 (maximum M 5.5) and the one in August 1998 (M 5.6). In addition, this area has many steep and unstable rocky terrain, and popular mountain climbing routes are concentrated, so there have been many accidents involving falling rocks. Therefore, it is necessary to make special preparations for earthquakes and falling rocks unique to this region. In this paper, we report on the damage caused by the earthquake and how climbers and mountain huts responded afterwards.