Preliminary results of multidisciplinary observations before, during and after the Kocaeli (Izmit) earthquake in the western part of the North Anatolian Fault Zone

Preliminary results of multidisciplinary observations before, during and after the Kocaeli (Izmit) earthquake in the western part of the North Anatolian Fault Zone

Y. Honkura1, A. M. Isikara2, N. Oshiman3, A. Ito4, B. Üçer2, S. Baris2, M. K. Tunçer2, M. Matsushima1, R. Pektas2, C. Çelik2, S. B. Tank2, F. Takahashi1, M. Nakanishi1, R. Yoshimura3, Y. Ikeda5, and T. Komut2

1Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo 152-8551, Japan
2Kandilli Observatory and Earthquake Research Institute, Bogaziçi University, Istanbul, Turkey
3Disaster Prevention Research Institute, Kyoto University, Kyoto 611-0011, Japan
4Faculty of Education, Utsunomiya University, Utsunomiya 321-0943, Japan
5Department of Geography, University of Tokyo, Tokyo 113-0033, Japan

(Received October 5, 1999; Revised February 19, 2000; Accepted March 9, 2000)

Abstract: On August 17, 1999, a destructive earthquake occurred in the western part of the North Anatolian Fault Zone, Turkey. The earthquake source region has been designated as a seismic gap and an M7-class earthquake has been supposed to occur someday in the future so as to fill this seismic gap. So far we have undertaken various kinds of observations in this area and we could obtain some valuable data before, during and after the mainshock. Here we report some of the preliminary results of our recent studies, which include field work started in late July this year and continued during and after the earthquake occurrence just in the earthquake source region and its vicinity, in addition to seismic observations carried out for several years before the mainshock. Much emphasis is put on magnetotelluric field data acquired during the mainshock; in fact, large variations caused by seismic waves were recorded. Such variations could be interpreted in terms of electromagnetic induction in the conducting crust caused by the velocity field interacting with the static magnetic field of the Earth. In particular, the first motion of seismic wave could be identified in the records and used for precise determination of the hypocenter of the mainshock.

orijinal link : Earth Planets Space, Vol. 52 (No. 4), pp. 293-298, 2000