The underground shelter was built by Japanese Imperial Army in 1943 in pyroclastic flow deposits resulting from nearby Singgalang and Merapiti Volcanoes. The Singkarak Lake earthquake, took place as two large shocks on March 6, 2007 and caused extensive damage to slopes in Sianok Valley, in which the underground shelter is situated. This article is concerned with the seismic effects on the underground shelter and its seismic response during the earthquake. A brief outline of geography, geology, the layout of the underground shelter and the shape and size of underground openings are fırst described. Then the characteristics of the earthquake are briefly presented. And then the seismic effects on the underground shelter is described. In the fınal part, the results of some preliminary dynamic numerical simulations for the response of the underground shelter during the earthquake are explained and discussed.
The West Sumatra Province of Indonesia was struck by an earthquake on March 6, 2007, killing 73 people and caused heavy damage in the cities of Solok, Payah Kumbuh, Batusangkar and Simabur[1]. Two large events with a moment magnitude of 6.4 and 6.3 occurred at an interval two hours on March 6, 2007[2,3]. The first author visited the epicentral area between Bukit Tinggi and Solok in July, 2007. This earthquake induced many slope failures in sceneric Sianok Valley in Bukit Tinggi. This valley was created by Sumatra fault cutting through pyroclastic flow deposits from nearby Volcanoes. In Sianok Valley Japanese Imperial Army built an underground shelter in the same geological formation in 1943. While there were many extensive slope failures along the valley, the damage to the underground shelter was almost none, which may be of great value for understanding the behaviour of underground openings during earhquakes. This article is written with a sole purpose of pointing out the importance of underground shelter as a rock engineering structure in weak rock and to discuss the long-term behaviour and dynamic response during the earthquake. There is no doubt that the evaluation of the long-tem stability and dynamic response of this underground shelter from a rock engineering perspective would provide an important data set. The geography, geology, the layout of the underground shelter, the shape and size of underground openings and underground climate and ventilation are briefly described. Then the rock classifications and static stability of assessments of the underground shelter are presented. And then, the characteristics of the earthquake, the seismic effects on the underground shelter and the results of some preliminary dynamic numerical simulations are explained and discussed.
This area is called the Padang Highland. A geologica1 sketch map of the area is shown in Figure 1, which was compiled by Sato [4] from the 1250000 quadrangle geologic maps published by the Geological Survey of Indonesia.
