SEGJ Technical Conference

Overview of the urgent disaster investigation in Iwaki City, Fukushima prefecture

Numerous ground caving and water flooding occurred after the 2011 Tohoku Earthquake, March 11, 2011, at old coal mine areas in Iwaki City, Fukushima Prefecture. Relatively shallow earthquake swarms have been observed over the old coal mine areas in southern Fukushima Prefecture and northern Ibaraki Prefecture since March 11. On April 11, large aftershocks occurred in Iwaki City and generated surface raptures along Idosawa Fault and Yunodake Fault. Sharp changes of flow-out rate of hot spring water were reported from surrounding spa resorts since then. Responding a request from the local government of Iwaki City, the Society of Exploration Geophysicists of Japan formed a voluntary team in order to carry out geophysical surveys in Iwaki City. The team has conducted shallow geophysical measurements at water flooding sites, earthquake monitoring over the ground caving and water flooding areas, and a CSAMT survey at Fujiwara Fault (southeastern extension of Yunodake Fault).