Calcul de l’aléa sismique pour une région dans le Tien-Shan Central, étude in situ et modélisation numérique dynamique de la réponse sismique de sites de bassin de retenue.

Kyrgyzstan is situated in the heart of the Tien Shan. During the last two centuries,
several M>7 earthquakes occurred in this country. Therefore, a good knowledge of seismic
hazard in this area is essential, not only at regional scale but also at local scale.
First, this work presents a detailed analysis of seismic hazard in the Central Tien Shan.
Several seismic hazard map have been made but none of them include paleoseismic data.
Our maps are based on previous studies of probabilistic seismic hazard of the Kyrgyz Tien
Shan (Abdrakhmatov et al., 2003). We integrate in our calculation the palaeoseismicity
of the Talas Fergana Fault. It allows us to take into consideration strong earthquakes
with high return periods. The final results are presented as maps with different return
periods (100, 200, 475, 1000, 2000, 5000 and 10000 years). The outcomes are discussed
in comparison with previous results, with GSHAP predictions (Ulomov et al., 1999) and
with probabilistic seismic hazard map (Abdrakhmatov et al., 2003).
The purpose of the second part of this study is the assessment of local seismic hazard
of Tuyuk-Suu and Taldy-Bulak "D" tailings, both located in the Minkush valley. First,
seismic wave amplifications are determined by means of spectral ratios of the horizontalto-
vertical (H/V) components acquired through ambient noise measurements. Secondly,
a dynamic modeling of the two tailings is performed. It is based on peak ground acceleration
calculated previously for a return period of 1000 years. The dynamic modeling gives
Fourier spectra for several histories. Spectral ratios obtained from dynamic modeling are
compared with H/V measurement in order to estimate site effects.