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Russian Geology and Geophysics

2011 year, number 9

STRONG HISTORICAL EARTHQUAKES IN THE NORTHWESTERN ISSYK KUL' BASIN ( northern Tien Shan )

A.M. Korjenkova, S.V. Abdievaa, P.S. Vakhrameevab, A.B. Dzhumabaevaa, E.M. Mamyrova, E.A. Morozovab, L.A. Orlovac, and A.B. Fortunaa
aInstitute of Seismology, National Academy of Sciences of the Kyrgyz Republic, Asanbai microdistrict 52/1, Bishkek, 720060, Kyrgyzstan
bSt. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg, 199034, Russia
cV.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Ancient earthquakes, Middle Ages, absolute dating, archeoseismology, paleoseismology, Lake Issyk Kul', Tien Shan
Pages: 1007-1015

Abstract

The northern Tien Shan is the northern front of the Himalayan mountain belt, which resulted fr om the collision between the Indian and Eurasian Plates. This region encompasses the most active seismic zones of the orogen, which generated the strongest ( M > 8) earthquakes. Since there are scarcely any written accounts, the only way to trace back strong earthquakes is the paleoseismological method. Since 1984 we have been studying the northwestern Issyk Kul' basin, wh ere there are differently directed anticlines, which constitute the Kungei megaanticline. Here, several active tectonic structures (faults, folds) are located, whose development was accompanied by strong earthquakes. Our field studies in 2008 in the Iiri-Taldybulak River valley, along the adyrs (foothills) of the Kungei-Ala-Too Range, revealed two unknown historical earthquakes. The first one, which occurred along the southern rupture in the late 7th century, gave rise to a seismic scarp; the latter broke through the river floodplain and a tash-koro (ancient settlement). The second one, which occurred along the northern rupture in the late 9th century, increased the height of the seismic scarp existing on the Early Holocene and older terraces. Note that this region already records a strong seismic event at ~500 A.D. Archeologic data have revealed one more strong earthquake, which took place in the 14th century. Note that the above-mentioned strong seismic events are coeval with the decline of the nomadic civilizatious (Wusun, Turkic, Mogul) in the northern Tien Shan and Zhetysu (Semirech'e).