Objective The uplift process and uplift mechanism of the Tibetan Plateau has been a research focus among geologists in recent years. This work put emphasis on the Cenozoic exhumation histories of the blocks bounded by...Objective The uplift process and uplift mechanism of the Tibetan Plateau has been a research focus among geologists in recent years. This work put emphasis on the Cenozoic exhumation histories of the blocks bounded by the major faults at the central segment of the Longmenshan thrust belt, and the vertical faulting history, including the starting time and the total vertical displacement, of the major faults. Then we quantitatively established a complete active process for the central segment of the Longmenshan thrust belt, combining with the previous geophysical data in the deep and geologcial data. This study is critical for deeply and completely understanding the Cenozoic uplift history of the Longmenshan, and also provides thermochronology constraints to the different models for the uplift of the eastern margin of the Tibetan Plateau.展开更多
In the epicenter of the Lushan MS7.0 earthquake there are several imbricate active reverse faults lying from northwest to southeast,namely the Gengda-Longdong,Yanjing-Wulong,Shuangshi-Dachuan and Dayi faults.Emergency...In the epicenter of the Lushan MS7.0 earthquake there are several imbricate active reverse faults lying from northwest to southeast,namely the Gengda-Longdong,Yanjing-Wulong,Shuangshi-Dachuan and Dayi faults.Emergency field investigations have indicated that no apparent earthquake surface rupture zones were located along these active faults or their adjacent areas.Only brittle compressive ruptures in the cement-covered pavements can be seen in Shuangshi,Taiping,Longxing and Longmen Townships,and these ruptures show that a local crustal shortening occurred in the region during the earthquake.Combining spatial distribution of the relocated aftershocks and focal mechanism solutions,it is inferred that the Lushan earthquake is classified as a typical blind reverse-fault earthquake,and it is advised that the relevant departments should pay great attention to other historically un-ruptured segments along the Longmenshan thrust belt and throughout its adjacent areas.展开更多
As revealed by field investigations,the co-seismic surface rupture zone of the 2010 MS7.1 Yushu earthquake,Qinghai is a characteristic sinistral strike-slip feature consisting of three distinct sinistral primary ruptu...As revealed by field investigations,the co-seismic surface rupture zone of the 2010 MS7.1 Yushu earthquake,Qinghai is a characteristic sinistral strike-slip feature consisting of three distinct sinistral primary ruptures,with an overall strike of 310°-320° and a total length of 31 km.In addition,an approximately 2-km-long en-echelon tensile fissure zone was found east of Longbao Town;if this site is taken as the north end of the rupture zone,then the rupture had a total length of ～51 km.The surface rupture zone is composed of a series of fissures arranged in an en-echelon or alternating relationship between compressive bulges and tensile fissures,with a measured maximum horizontal displacement of 1.8 m.The surface rupture zone extends along the mapped Garzê-Yushu Fault,which implicates it as the seismogenic fault for this earthquake.Historically,a few earthquakes with a magnitude of about 7 have occurred along the fault,and additionally traces of paleoearthquakes are evident that characterize the short-period recurrence interval of large earthquakes here.Similar to the seismogenic process of the 2008 Wenchuan earthquake,the Yushu earthquake is also due to the stress accumulation and release on the block boundaries resulting from the eastward expansion of Qinghai-Tibet Plateau.However,in contrast with the Wenchuan earthquake,the Yushu earthquake had a sinistral strike-slip mechanism resulting from the uneven eastward extrusion of the Baryan Har and Sichuan-Yunnan fault blocks.展开更多
基金supported by the National Natural Science Foundation of China(grant No.41302159)
文摘Objective The uplift process and uplift mechanism of the Tibetan Plateau has been a research focus among geologists in recent years. This work put emphasis on the Cenozoic exhumation histories of the blocks bounded by the major faults at the central segment of the Longmenshan thrust belt, and the vertical faulting history, including the starting time and the total vertical displacement, of the major faults. Then we quantitatively established a complete active process for the central segment of the Longmenshan thrust belt, combining with the previous geophysical data in the deep and geologcial data. This study is critical for deeply and completely understanding the Cenozoic uplift history of the Longmenshan, and also provides thermochronology constraints to the different models for the uplift of the eastern margin of the Tibetan Plateau.
基金supported by the National Natural Science Foundation of China(91214201 and 40821160550)the Special Fund for Scientific Investigation of the Lushan Earthquake
文摘In the epicenter of the Lushan MS7.0 earthquake there are several imbricate active reverse faults lying from northwest to southeast,namely the Gengda-Longdong,Yanjing-Wulong,Shuangshi-Dachuan and Dayi faults.Emergency field investigations have indicated that no apparent earthquake surface rupture zones were located along these active faults or their adjacent areas.Only brittle compressive ruptures in the cement-covered pavements can be seen in Shuangshi,Taiping,Longxing and Longmen Townships,and these ruptures show that a local crustal shortening occurred in the region during the earthquake.Combining spatial distribution of the relocated aftershocks and focal mechanism solutions,it is inferred that the Lushan earthquake is classified as a typical blind reverse-fault earthquake,and it is advised that the relevant departments should pay great attention to other historically un-ruptured segments along the Longmenshan thrust belt and throughout its adjacent areas.
基金supported by the management and other functions of the Institute of Geology,CEA
文摘As revealed by field investigations,the co-seismic surface rupture zone of the 2010 MS7.1 Yushu earthquake,Qinghai is a characteristic sinistral strike-slip feature consisting of three distinct sinistral primary ruptures,with an overall strike of 310°-320° and a total length of 31 km.In addition,an approximately 2-km-long en-echelon tensile fissure zone was found east of Longbao Town;if this site is taken as the north end of the rupture zone,then the rupture had a total length of ～51 km.The surface rupture zone is composed of a series of fissures arranged in an en-echelon or alternating relationship between compressive bulges and tensile fissures,with a measured maximum horizontal displacement of 1.8 m.The surface rupture zone extends along the mapped Garzê-Yushu Fault,which implicates it as the seismogenic fault for this earthquake.Historically,a few earthquakes with a magnitude of about 7 have occurred along the fault,and additionally traces of paleoearthquakes are evident that characterize the short-period recurrence interval of large earthquakes here.Similar to the seismogenic process of the 2008 Wenchuan earthquake,the Yushu earthquake is also due to the stress accumulation and release on the block boundaries resulting from the eastward expansion of Qinghai-Tibet Plateau.However,in contrast with the Wenchuan earthquake,the Yushu earthquake had a sinistral strike-slip mechanism resulting from the uneven eastward extrusion of the Baryan Har and Sichuan-Yunnan fault blocks.
