Abstract
A strong earthquake measuring a magnitude of 7.8 on the Richter scale shook areas of Kushiro in Hokkaido at January 15, 1993. The epicenter was located at 17km off Kushiro city, and the focal depth was about 107km. The Taiheiyo Coal Mine is located at the east end of Kushiro city. At the very moment of earthquake occurred, about 450 over coal miners worked in a variety of the deep pits about 600m below the seabed.
To clarify the seismic intensity in deep underground space, a questionnaire seismic intensity survey was carried out to 31 Taiheiyo coal miners.Although Japan Meteorological Agency reported the maximum ground intensity of 6 at Kushiro areas, the obtained average seismic intensity in a underground of 600m was 3.1.
