Abstract
On May 27, 2006, the Mid Java Earthquake hit around Jogjakarta City in Java Island, Indonesia. In this report, results from field investigations on geotechnical issues conducted by the Japanese Geotechnical Society survey team are summarized. At several sites where liquefaction occurred in lowland areas, subsurface soil conditions consisting of high groundwater table with soft soil deposits were identified. The liquefaction caused frequent plugging of wells. In these lowland areas, high collapse ratio of houses was reported, which may be linked to the directivity of earthquake motions affected by the earthquake fault location and/or their amplification in the soft soil deposits. In mountainous areas, a large scale landslide and a large number of slope failures and rock falls occurred. Earth fill dams suffered from cracking at the crest, while the rate of the leakage water from the toe of the downstream slope was not changed. Some recommendations are made in conducting detailed analyses and executing rehabilitation works on the damaged dams.
