Strong Earthquakes on the Southern Slope of the Kungei Ala-Too Range, Northern Tien Shan, and Their Structural Position in the Earth’s Crust

Strong Earthquakes on the Southern Slope of the Kungei Ala-Too Range, Northern Tien Shan, and Their Structural Position in the Earth’s Crust

The morphostructures and paleoseismicity of the southern slope of the Kungei Ala-Too Range (Northern Tien Shan) have been studied. It has been found that the main seismogenic structures in the Late Pleistocene and Holocene were adyr (foothill) faults, that is, thrusts, strike-slips, and normal dips....

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Bibliographic Details
Published in:Izvestiya. Atmospheric and oceanic physics Vol. 58; no. 7; pp. 724 - 747
Main Authors: Korzhenkova, L. A., Korzhenkov, A. M., Strelnikov, A. A., Starikova, A. Yu, Kichutkin, A. S., Makeev, V. M., Mazheika, J. V., Fortuna, A. B.
Format: Journal Article
Language:English
Published: Moscow Pleiades Publishing 01-12-2022
Springer Nature B.V
Subjects:
Carbon 14
Climatology
Comparative analysis
Earth and Environmental Science
Earth crust
Earth Sciences
Earth surface
Earthquakes
Escarpments
Fault detection
Fault lines
Faults
Foothills
Geological faults
Geophysics/Geodesy
Graben
Hanging walls
Holocene
Mountains
Paleogeology
Pleistocene
Radiocarbon dating
Seismic activity
Slopes
Trenching
underthrusts
trenching
Tien Shan
strong earthquakes
ramp graben
Terskey Ala-Too
Issyk-Kul
archeoseismology
radiocarbon dating
fault scarps
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Summary:The morphostructures and paleoseismicity of the southern slope of the Kungei Ala-Too Range (Northern Tien Shan) have been studied. It has been found that the main seismogenic structures in the Late Pleistocene and Holocene were adyr (foothill) faults, that is, thrusts, strike-slips, and normal dips. With a general thrusting of block folds of the basement southwards (toward the Issyk-Kul Basin), there are also northward-moving underthrusts. The past seismic activity along the adyr faults is expressed by single seismogenic scarps, as well as by stair-like series of alluvial-proluvial and fluvioglacial surfaces, upthrown in the hanging walls of faults. In addition to the easily identifiable vertical component of slips along the faults, we have also identified significant horizontal slips, which often greatly exceed the vertical ones. In addition, a unique structure, that is, a neotectonic ramp graben bounded from the south and north by oppositely directed thrusts, was studied on the slope of the Kungei Range. The mentioned faults were also studied by trenching. It was found that in the middle–second half of the Holocene three strong morphogenetic seismic events occurred on the South Tegerek adyr fault and three strong earthquakes occurred on the North Tegerek adyr fault. The ages of four strong earthquakes were determined by the radiocarbon method. The maximum ages of the first three events are 3970–3755 BC, 220–405 AD, and 1380–1450 AD, while the minimum age of the last event is 1720–1815 AD. The magnitudes of historical and paleoearthquakes that occurred on the studied adyr faults range from M  = 6.6–6.9 ± 0.5 (South Tegerek fault) to M  = 6.8–7.4 ± 0.5 (Kultor adyr fault). Seismic events of similar magnitudes lead to deformations of the earth’s surface and in building constructions, which can be estimated on a macroseismic scale at I  ≥ IX. Our data obtained in this study can be used for a comparative analysis of similar post-platform orogens in Russia (e.g., Altay and Sayan mountains), as well as in compiling the new general seismic zoning map for the Kyrgyz Republic.
ISSN:0001-4338
1555-628X
DOI:10.1134/S0001433822070064