Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault （LSPF）, one of the most active faults in the Hetao fault zone in Inner Mongol...Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault （LSPF）, one of the most active faults in the Hetao fault zone in Inner Mongolia, North China. The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history. Using cosmogenic ^10Be exposure dating, we measured the exposure ages of the western Langshankou scarp, located in the middle segment of the LSPF. Our data revealed at least two earthquakes that occurred at 22.2±3.3 Ira and 7.2±2.4 ka, respectively. These events are consistent with previous paleoseismic trench studies. The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 ±0.05/-0.06 mm/yr, which is significantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr, as estimated from the offset of the T2 terraces by previous studies. This indicates that the slip of the LSPF may have been accommodated by other fault branches.展开更多
The Heqing-Eryuan fault is an important part of the active fault system in the Northwestern Yunnan Province, China. Thus, the study on the nature, characteristics and activity history of this fault can provide not onl...The Heqing-Eryuan fault is an important part of the active fault system in the Northwestern Yunnan Province, China. Thus, the study on the nature, characteristics and activity history of this fault can provide not only the basis for seismic safety and engineering evaluation, but also the important information for the characteristics, history and patterns of the structural deformation of the southeastern margin of the Tibetan Plateau. Trench and faulted landforms investigations could provide effective paleoseismic methods to obtain the recent parameters of active faults. Using these methods, this study makes some breakthroughs on the recent activity of southeast boundary fault of the Heqing basin, middle segment of Heqing-Eryuan fault zone. Results indicate that the average vertical slip rate and left-lateral slip rate of the segment are about 0.28 mm/a and 1.8o mm/a respectively since the Late Pleistocene. The trench near the Beixi Village at the .outhea.t houndnrv fault of the lqaaing basinreveals that there have been at least three paleoearthquake events during the Holocene （8 ka BP）. The vertical displacement and sinistral strike-slip distance of a single paleoearthquake are ~20 cm and -1.2 m, respectively. The estimated paleoearthquake magnitudes with Ms7.o, and the recurrence interval at 2-5 ka, as well as the latest activity time during 800- 290 ca1 yr BP, are of great significance for preventing and mitigating regional earthquake disasters.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.41171001)the 1:50000 Active Fault Mapping of Langshan Piedmont Fault (Grant No.201408023)the Basic Research Business Foundation of the China Earthquake Administration (Grant No.ZDJ2012-02)
文摘Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault （LSPF）, one of the most active faults in the Hetao fault zone in Inner Mongolia, North China. The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history. Using cosmogenic ^10Be exposure dating, we measured the exposure ages of the western Langshankou scarp, located in the middle segment of the LSPF. Our data revealed at least two earthquakes that occurred at 22.2±3.3 Ira and 7.2±2.4 ka, respectively. These events are consistent with previous paleoseismic trench studies. The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 ±0.05/-0.06 mm/yr, which is significantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr, as estimated from the offset of the T2 terraces by previous studies. This indicates that the slip of the LSPF may have been accommodated by other fault branches.
基金supported by the National Natural Science Foundation of China (Grant No. 41171001, 41471002, 41402184)the 1:50000 Active Fault Mapping of HeqingEryuan fault (Grant No. 201108001-20)a research grant from the Institute of Crustal Dynamics, China Earthquake Administration (Grant No. ZDJ2013-17)
文摘The Heqing-Eryuan fault is an important part of the active fault system in the Northwestern Yunnan Province, China. Thus, the study on the nature, characteristics and activity history of this fault can provide not only the basis for seismic safety and engineering evaluation, but also the important information for the characteristics, history and patterns of the structural deformation of the southeastern margin of the Tibetan Plateau. Trench and faulted landforms investigations could provide effective paleoseismic methods to obtain the recent parameters of active faults. Using these methods, this study makes some breakthroughs on the recent activity of southeast boundary fault of the Heqing basin, middle segment of Heqing-Eryuan fault zone. Results indicate that the average vertical slip rate and left-lateral slip rate of the segment are about 0.28 mm/a and 1.8o mm/a respectively since the Late Pleistocene. The trench near the Beixi Village at the .outhea.t houndnrv fault of the lqaaing basinreveals that there have been at least three paleoearthquake events during the Holocene （8 ka BP）. The vertical displacement and sinistral strike-slip distance of a single paleoearthquake are ~20 cm and -1.2 m, respectively. The estimated paleoearthquake magnitudes with Ms7.o, and the recurrence interval at 2-5 ka, as well as the latest activity time during 800- 290 ca1 yr BP, are of great significance for preventing and mitigating regional earthquake disasters.
