A Detailed Study on the Liquefaction-Induced Settlement of Timber Houses During the 2000 Tottoriken-Seibu Earthquake

More than 100 timber houses settled and tilted due to liquefaction at a housing development during the 2000 Tottoriken-seibu earthquake in Japan. Among the damaged houses, 47 houses tilted more than 15/1000. Heavily tilted houses were necessary to restore to become horizontal after the earthquake, though several houses, that tilted slightly, were not necessary to restore. The authors studied the boundary of the angle of the restored and non-restored houses. According to the study by the authors, the critical angle of tilting to restore houses was about 10/1000. The authors studied soil conditions also, and found that groundwater level was shallower than about 1.7 m in the damaged zone. This implies that small structures such as timber houses have no damage due to liquefaction if the groundwater level or the bottom of surface non-liquefiable layer is deeper that about 1.7 m