Journal of the Japan Society of Erosion Control Engineering, Vol.56,No.3,2003

The sediment-related disaster Caused by earthquake in the offing the northern part of Miyagi prefecture in July, 2003 (prompt report)

Michiya IRASAWA, Motoyuki USHIYAMA, Kazuki MATSUMURA, Hiroshi KAWABE, Shinya HIRAMATSU, Daisuke HIGAKI

Abstract
The earthquake of magnitude 5.5 (12km deep of seismic center) hit at about 00:13 on July 26, 2003, was centered in the northern part of Miyagi. The recorded seismic intensity was a little less than 6 in Ono Naruse-cho, Yamoto Yamoto-cho, Miyagi prefecture. Furthermore the earthquake of magnitude 6.2 (12km deep of seismic center) was almost centered at the same places at 07:13 on the same day. The seismic intensity of this earthquake was a little over 6 on Naruse-cho, Yamoto Yamoto-cho, Kibazuka Nango-cho. In addition, the earthquake of magnitude 5.3 (12km deep of seismic center) was centered at the almost same place at 16:56 on the same day. By this earthquake, we recorded the seismic intensity a little less than 6 in Maeyachi Kanan-cho. In this way, there were three times earthquakes in a day, the seismic intensity with a little less than 6 and a little over 6. It is the first time in a history of internal seismometry in such a continuation earthquake. By this earthquake, 674 persons were injured (50 serious wounds/624 slight wounds). And the dwelling house damage were 1,017 complete destruction, partial destruction2,245,8,078 one part damage (the August 29 present). We showed off terror of earthquake directly above its epicenter in the inland. Such damage concentrated on Miyagi prefecture. By an earthquake directly above its epicenter in this inland, sediment disaster occurred in each place in North Miyagi districts such as Kanan-cho, Yamoto-cho, Naruse-cho. The Japan Society of Erosion Control Engineering dispatched the disaster Investigating commission about slope collapse by the earthquake of 2003.7.26 North Miyagi in order to grasp the general conditions of sediment disasters by the earthquakes. We reorganize the disaster investigating commission, “Slope collapse investigation commission by the earthquake of the 2003.5.26 offshore of Miyagi prefecture" to “Slope collapse investigation commission by the earthquake of the 2003.5.26 offshore of Miyagi prefecture and the earthquake of 2003.7.26 North Miyagi prefecture".This paper summarized the investigations related to the property to the earthquake damages, focused on slope failures in hilly areas.

Key words:Tohoku district, Miyagi prefecture, earthquake, sediment-related disaster, slope failure, earthquake directly above its epicenter in this inland