The 2007 Noto Peninsula, Japan, Earthquake (Mw 6.7): Damage to Wooden Structures

Abstract

The 2007 Noto Peninsula earthquake ( Mw 6.7, M jma 6.9) produced strong shaking throughout central Japan with substantial damage to more than 14,500 buildings. The shallow event occurred close to the Japan Sea coast (37.22°N, 136.69°E, depth 11 km) on 25 March 2007 at 00:41:58 GMT. Analyses of seismic data showed that it was a thrust fault (striking northeast and dipping downward to the southeast) with dimensions of about 15 × 30 km2 (figure 1; Aoi and Sekiguchi 2007). There was no significant surface faulting from the earthquake but Global Positioning System measurements showed surface displacements of 20 to 25 cm (Geographical Survey Institute 2007). The recent seismicity of the Noto Peninsula region has been relatively low and has included moderate events in 1933 ( Mjma 6.0) and 1993 ( M jma 6.6). For the latest earthquake, there were significant strong ground motions throughout the Noto Peninsula (figure 1), with maximum recorded ground velocities of 80 to 100 cm/s. Although the region is a relatively sparsely populated area of Japan, there was considerable damage to wooden structures, the predominant type of construction. There were 630 totally and 13,920 partially collapsed buildings, with damage concentrated in the towns of Monzen and Anamizu and lesser damage in downtown Wajima (Cabinet Office, Government of Japan 2007a). The cost of the total damage is estimated to be ¥65 billion (about U.S. $535 million) (Cabinet Office, Government of Japan 2007b). Despite the large number of severely damaged houses, there was only one fatality (not related to a building collapse) and 336 injured. As has been the case with other recent earthquakes in Japan, several groups quickly carried out detailed surveys of building damage. This paper presents some statistical results about damage to wooden structures from the Noto Peninsula earthquake, which characterizes the fragility …