1995年10月18日, 19日の奄美大島近海の地震(M6.6, M6.5)の前震および余震活動について Foreshock and Aftershock Activity of the Near Amami-Oshima Earthquakes on 18 and 19 October 1995
An earthquake with <I>M</I>6.6 occurred about 50 km southeast off Kikai-jima which is located near Amami-Oshima in Kagoshima prefecture at 19 : 37 October 18, 1995. About 16 hours after the event, an another earthquake with <I>M</I>6.5 occurred in the same region. Seismic intensity of 5 in the JMA scale was recorded at Takigawa in Kikai-jima for the two earthquakes. Focal mechanisms of the two earthquakes were normal fault-type, and they were estimated to have had occurred within the Philippine Sea plate. Tsunamis were observed at Pacific coasts in southwest Japan. Tsunami waves were higher than usual at Kikai-jima, relative to seismic magnitude, at the two earthquakes. Characteristics of the seismic activity before and after the near Amami-Oshima earthquake are summarized as follows : <BR>1. Preceding seismic activity and foreshocks were observed.<BR>2. Another earthquake with almost the same magnitude succeeded after a short interval.<BR>3. Following characteristic patterns were recognized in seismicity : <BR>Seismicity was decreased noticeably in the northeastern part of the aftershock area just before larger shocks over <I>M</I>5. While conspicuous decrease in seismicity was observed in the southwestern part of the aftershock area after the earthquake of <I>M</I>6.5.
地學雜誌 106(4), 465-475, 1997-08-25
Tokyo Geographical Society