Dip-slip rate determined by cosmogenic surface dating on a Holocene scarp of the Daju fault, Yunnan, China

摘要

The Daju and Lijiang-Daju fault zones which bound the Yulong Mountains on its northern and eastern perimeters, respectively, are segments of a continuous fault system that bends at Daju. Uplift of the Yulong Mountains, the southernmost glacierized mountain range in Eurasia, resulted from the normal faulting characteristics of the fault system. Using cosmogenic surface exposure dating with ~(10)Be and ~(26)Al, we have measured bedrock exposure ages as a function of elevation along an exposed bedrock scarp of the Daju fault. ~(10)Be and ~(26)Al exposure ages increase monotonically with elevation ranging from 2.6 to 9.6ka over the 51m scarp length giving an average dip-slip rate of 7.5m/ka during the Holocene period and a vertical uplift rate of 5.7m/ka. The 5.7m/ka Holocene uplift rate and supporting geomorphic features suggest that the uplift of the Yulong Mountains mainly occurred in the Quaternary. The fast slip rate and seismic quiescence for the recent 2.8ka call attention to the possible recurrence of large magnitude earthquake events along the fault zone.