A study of the Late Pleistocene action of Yaluhe fault in northern Da Hinggan Mountains

The Yahuhe fault in northern Da Hinggan Mountains is a typical active fault, and it is of significance in the study of the Late Pleistocene regional geological and geomorphologic evolution and modern earthquake. The authors discovered the active records of Yaluhe fault on the east of Yalu River in northern Genghis Khan Town of Zhalantun City. In this paper, on the basis of detailed field data, the authors determined the fault activity characteristics and time limit through the OSL dating of loose deposits, and estimated the ancient seismic features of the fault active records combined with relevant experience formula. The study results show that the movement of Yaluhe fault in the south of Zhalantun occurred in the Late Pleisotocene. The fault is nearly SN-striking, with dip 55° and dip angle 265°, being a thrust fault. The fault dislocated Mesozoic rhyolite and early to middle Late Pleistocene pluvial-alluvial deposits, and was covered by the Late Pleistocene eluvial and alluvial deposits. The fault happened at 53.4±6.7~39.1±3.6ka. As active record reflected, the ancient seismic moment magnitude (M₀) and surface wave magnitude (Ms) was about 6.7, and surface rupture length (SRL) was about 30.2~37.8km at the time of the earthquake.