Characteristics and dynamics of the Ganqiuchi rock avalanche triggered by a paleo-earthquake in the Northern Qinling Mountains Characteristics and dynamics of the Ganqiuchi rock avalanche triggered by a paleo-earthquake in the Northern Qinling Mountains

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Vol17 No.5: 1143-1160

Title】Characteristics and dynamics of the Ganqiuchi rock avalanche triggered by a paleo-earthquake in the Northern Qinling Mountains

Author】ZHOU Ze-Hua1; LYU Yan1*; SU Sheng-rui1; LIU Shi-jie1; ZHAO Hui2; LI Peng1; ZHOU Yang1

Addresses】1 School of Geology Engineering and Geomatics, Chang'an University, Xi'an 710054, China; 2 The Geopark of Shaanxi Cuihua Mountain, Xi'an 710054, China

Corresponding author】LYU Yan

Citation】Zhou ZH, Lyu Y, Su SR, et al. (2020) Characteristics and dynamics of the Ganqiuchi rock avalanche triggered by a paleo-earthquake in the Northern Qinling Mountains. Journal of Mountain Science 17(5). https://doi.org/10.1007/s11629-019-5599-0

DOI】https://doi.org/10.1007/s11629-019-5599-0

Abstract】Analyzing large prehistoric rock avalanches provides significant data for evaluating the disaster posed by these relatively infrequent but destructive geological events. This paper attempts to study the characteristics and dynamics of the Ganqiuchi granitic rock avalanche, in the middle of the northern margin of Qinling Mountains, 30 km to the south of Xi'an, Shaanxi Province, China. In plane view, this rock avalanche is characterized by source area, accumulation area and dammed lake area. Based on previous studies, historical records and regional geological data, the major trigger of the Ganqiuchi rock avalanche is considered to be a strong paleo-earthquake with tremendous energy. The in situ deposit block size distributions of the intact rock mass and the debris deposits are presented and analyzed by using a simple model for estimating the number of fragmentation cycles that the blocks underwent. The results show that the primary controlling factor of the fragmentation process is the pre-existing fractures, and there is a relationship between the potential energy and the fragmentation energy: the latter is approximately 20% of the former. Based on the dynamic discrete element technique, the study proposes a four-stage model for the dynamic course of the Ganqiuchi rock avalanche: (1) failing; (2) high-speed sliding; (3) collision with obstacles; (4) decelerated sliding, which has implication for hazard assessment of the potential rock avalanches in China and other countries with similar geological setting.

Keywords】Ganqiuchi rock avalanche; Deposit block size distribution; Fragmentation; Discrete element method; Rock avalanche dynamics