| Co-Investigator(Kenkyū-buntansha) |
YANUAR Meteorological and Geophysical Agency of Indonesia, Medan, Chief, パラパト観測所, 所長
SYNARJO Meteorological and Geophysical Agency of Indonesia, Jakarta, Chief Technical off, 主任研究員
SOETARDJO R. Meteorological and Geophysical Academy of Indonesia, Jakarta, Associate Chief, 次長
GUSIAKOV V.K. Academy of Science of Russia, Computer Center Novosibirsk, Technical official, 上級研究員
IVASHENKO A.I. Academy of Science of Russia, Institute of Marine Geology & Geophysics, Yuzhno-S, 地球物理研究所, 副所長
MIYATAKE Takashi Earthquake Research Institute, The University of Tokyo, Lecturer, 地震研究所, 講師 (60126183)
TAKEO Minoru Earthquake Research Institute, The University of Tokyo, Associate Professor, 地震研究所, 助教授 (00197279)
SHIMAZAKI Kunihiko Earthquake Research Institute, The University of Tokyo, Professor, 地震研究所, 教授 (50012951)
SUETSUGU Daisuke Building Research Institute Technical official, 建設技官(研究職)
NAKANISHI Ichiro Faculty of Science, Hokkaido University, Associate Professor, 理学部, 助教授 (10164229)
MORIYA Takeo Faculty of Science, Hokkaido University Associate Professor, 理学部, 助教授 (60001864)
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| Research Abstract |
Digital broadband seismograms are more or less continuously recorded at Yuzhno-Sakhalinsk in Russia and at Parapat, northern Sumatra, Indonesia. Parapat station is characterized by low noise at night, but large-amplitude noises appear for several hours in day time. Although the comparison between time of the day when the noises appear and daily temperature measured at Parapat did lead to a firm conclusion, the 1/f dependence of noise spectrum strongly suggests that the noises are due to temperature fluctuations caused by the radiative heat of the sun light.
The Russian and Japanese sides agree on that the second site for cooperative broadband seismic observation between Russia and Japan should be Kamenskoye in northern Kamchatka. The valuable data concerning the tsunami and aftershocks of the 1993 Japan Sea earthquake were successfully exchanged between Russian and Japanese scientists.
On the basis of the three-dimensional seismic velocity structure obtained by us, broadband digital seismograms at Parapat for various propagation paths are examined. The seismograms of Halmahere events show strong attenuation, which is consistent with very low seismic wave velocity in the Straits of Molucca shown in the three-dimensional structure.
Waveform analyses of digital broadband seimograms indicate that the 1993 Kushiro-Oki earthquake is characterized by high stress drop and that the 1993 Japan Sea earthquake is characterized by a marked differecne between the initial and overall rupture processes.
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