The Occurrence of Large Holocene Earthquakes in the Kultor Fault Zone, Northern Issyk-Kul Area, Tien Shan Based on Radioisotope Dating

Abstract

Structural-geomorphological and paleoseismological methods were used to study morphostructures on the southern slope of the Kungei Ala-Too mountain range and in its southern foothills (adyrs). An analysis of radioisotope dates (radiocarbon and infrared luminescence) in paleoseismological trenches shows a lateral migration of vigorous seismic activity along the Kultor fault zone in the northern Issyk-Kul region. It has been confirmed that the contemporary high seismic activity concentrates in the adyr zone, and is confined to adyr faults. At least seven morphogenic earthquakes have occurred along this fault zone during Holocene time. The repeat time of morphogenic earthquakes was 200‒300 years in our era. It seems that this fault generated great seismic disasters with М ~ 7.5 (Io = Х) in the 7th and 15th centuries, with the rupture zones emerging at the surface and producing fault scarps up to 70‒80 km in length.