Precise Distribution of Aftershocks of the Izmit Earthquake of August 17, 1999, Turkey

HR: 13:45h
AN: S12D-02
TI: Precise Distribution of Aftershocks of the Izmit Earthquake of August 17, 1999, Turkey
AU: * Ito, A
EM: ito@cc.utsunomiya-u.ac.jp
AF: Facuty of Education, Utsunomiya University, Utsunomiya, 321-8505 Japan
AU: Ucer, B
AF: Kandilli Observatory and Earthquake Research Institute, Bogazici University, Istanbul, Turkey
AU: Baris, S
AF: Kandilli Observatory and Earthquake Research Institute, Bogazici University, Istanbul, Turkey
AU: Honkura, Y
AF: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokoy, 152-8551 Japan
AU: Kono, T
AF: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Tohoku University, Sendai, 980-8578 Japan
AU: Nakamura, A
AF: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Tohoku University, Sendai, 980-8578 Japan
AU: Pektas, R
AF: Kandilli Observatory and Earthquake Research Institute, Bogazici University, Istanbul, Turkey
AU: Ishikawa, Y
AF: Facuty of Education, Utsunomiya University, Utsunomiya, 321-8505 Japan
AU: Isikara, A
AF: Kandilli Observatory and Earthquake Research Institute, Bogazici University, Istanbul, Turkey

Abstract

AB: On August 17, 1999, a destructive earthquake occurred in the western part of the North Anatolian Fault Zone (NAFZ), Turkey. The source region of the earthquake has been designated as a seismic gap. We have been operating a radio-linked seismic network, called IZINET, since 1992 in order to monitor the seismicity in this seismic gap. IZINET was only one, and also digital, seismic network that was operated surrounding the hypocenter of the main shock when it has occurred. Therefore, we have recorded the aftershock sequence just after the main shock. In addition to the telemetering observation, we have installed 10 temporary seismic stations since August 21 along the source region. By combining the data of IZINET and these temporary observations, we have got a very precise hypocenter distribution of aftershocks. Major aspects of the aftershock distribution were as follows; \begin{enumerate} \item Aftershocks have been taking place linearly along the trace of surface rupture in the middle part of the source region. In the western part, the aftershock region also extends linearly from the Izmit bay up to about N29.1, where would be considered as the western end of the rupture of the main shock. \item In the eastern part, aftershocks occur no longer along the surface rupture but rather seems to scatter widely. The southern edge of the aftershock expansion in this part seems to be aligned to one of branches of NAFZ, while the northern edge seems to correspond to the surface rupture. \item The eastern-most portion of the aftershock region extends in the northeastern direction along the other branch of NAFZ and reaches up to about E31.0. \end{enumerate} Above features of the aftershock distribution suggest that the whole length of rupture zone of the main shock has been about 150 km. This conclusion is, however, a little different from other results obtained by waveform inversion analyses. We need to discuss how we can understand the source process with fewer inconsistencies.

DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics and mechanics
DE: 7230 Seismicity and seismotectonics
SC: S
MN: 1999 AGU Fall Meeting