HR: 11:35h
AN: S22B-05    [Abstracts]
TI: Effect of Fault Zone on Strong Ground Motion
AU: * Bouchon, M
EM: Michel.Bouchon@ujf-grenoble.fr
AF: Universite Joseph Fourier, BP 53, Grenoble, 38041 France
AU: Karabulut, H
EM: kara@boun.edu.tr
AF: Bogazici University , Kandilli Observatory, Istanbul, 81220 Turkey
AU: Dietrich, M
EM: Michel.Dietrich@ujf-grenoble.fr
AF: Universite Joseph Fourier, BP 53, Grenoble, 38041 France
AU: Bouin, M
EM: bouin@ipgp.jussieu.fr
AF: Institut de Physique du Globe, 4 Place Jussieu, Paris, 75252 France
AU: Aktar, M
EM: aktar@boun.edu.tr
AF: Bogazici University , Kandilli Observatory, Istanbul, 81220 Turkey
AB: During the M=7.2 Duzce earthquake and its early aftershocks, we recorded the ground accelerations at a small array located within the fault zone of the Izmit earthquake. The array was about 25km away from the Duzce epicenter and consisted of 4 stations set a few hundred meters apart. The stations were all located within about 150m from the fault trace and one of them was installed on the fault trace itself. Peak horizontal acceleration during the main shock was 0.3g at the furthest station from the fault but drastically increased to about 1.0g on the fault itself. Likewise, during the many recorded aftershocks, peak acceleration shows a regular and drastic increase as the recording site is located closer and closer to the fault. During the strongest recorded aftershock, for instance, peak values continuously increase from 0.21g, to 0.34g, to 0.62g, and to about 1.0g, as the distance of the site to the fault trace decreases from about 150m to 0m. These observations show that the fault zone is a narrow structure which extends over a distance of about 100m from the fault trace and which considerably increases the ground shaking close to the fault. This result is in agreement with the study of fault-zone trapped waves made by Ben-Zion et al. (2003) along the same fault segment. The present results also show that the fault zone is not a homogeneous low-velocity wedge, but is a zone of continuously degrading elastic stiffness as one approaches the fault trace.
DE: 7223 Seismic hazard assessment and prediction
DE: 7209 Earthquake dynamics and mechanics
DE: 7212 Earthquake ground motions and engineering
SC: Seismology [S]
MN: 2004 AGU Fall Meeting