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2008 Bilateral Workshop under the Sino - US Earthquake Studies Protocol TECTONIC DEFORMATION OF THE TIBET PLATEUA AND THE WENCHUAN EARTHQUAKE REN Jinwei and Xiong Renwei Institute of Earthquake Science, CEA, Beijing 100036, China Email: [email protected] Sun Xiong and Song Xiaoming Earthquake Administration of Qinghai Province, Xi'nin 810001, China November 11-14, 2008 Boulder, Colorado, USA Active Tectonics of Tibetan Plateau Fault scarp in the Gulu Basin (Dangxiong graben) Fault scarp in the Gulu Basin (Dangxiong graben) Fault scarp in the Gulu Basin (Dangxiong graben) Fault scarp in Wenquan (hot spring) basin Linear tufa in Wenquan (hot spring) basin A 4200 4155 4122 A’ 4143 3996 A’ A 2.5km Air photograph of Ranwu area, south-eastern Tibet North-western segment of Jiali fault Landslides along the normal fault at Daren Basin Scarps along the Jiali fault T3 Fault scarp T2 T1 Fault scarp along the BNS (south of Tanggula) In the southern part of the Tibetan plateau (Lhasa terrane and BangongNujiang suture), the deformation is dominated by east-west extension The deformation is occurred throughout the Lhasa terrane, along the suture the deformation is not significant The strike slip motion of the faults in this area is most likely related to the extension Active Tectonics of Tibetan Plateau Thrust fault along the Jinsha Suture (south of Erdaogou) Deformation of the alluvium south of Erdaogou Along the Jinsha suture, neo-tectonic deformation is dominated by the thrust faulting and it mainly occurred along the suture Within the Qiangtang terrane, the deformation is minor Active Tectonics of Tibetan Plateau The highway was offset 3m by the ruptures at Kunlun Pass 5.8 m Surface Ruptures Left lateral displacement 90km west of Kunlun Pass Surface ruptures along the Kunlun pass fault by 2001 earthquake Active Tectonics of Tibetan Plateau Surface ruptures along the east Kunlun fault by 1937 earthquake Surface ruptures along the east Kunlun fault by 1937 earthquake Surface ruptures along the east Kunlun fault by 1937 earthquake Surface ruptures along the east Kunlun fault by 1937 earthquake Active Tectonics of Tibetan Plateau Surface ruptures along the east Kunlun fault near Maqin Surface ruptures along the east Kunlun fault eastof Maqin Surface ruptures along the east Kunlun fault east Maqin Surface ruptures along the east Kunlun fault near Maqin Along the Kunlun suture, neo-tectonic deformation is dominated by left lateral strike slip faulting and it mainly occurred along the suture large earthquakes occurred along the east Kunlun fault in the last century, the surface ruptures caused by these events had almost gone through the entire fault Crust Movement of China Continent GPS Data from CMONOC Fold caused by the strike slip motion by 2001 earthquake Large Earthquakes along the Kunlun Fault 2001/8.1 1963/7.0 ????/>7.5 1937/7.5 1947/7.5 CONCLUSION REMARKS The crust deformation of the Tibetan plateau is dominated by east-west extension in the southern part and the material in northern part of the plateau has been penetrated eastward. The eastward flow is separated by several large left-lateral strike-slip faults. Once the movement of the blocks between the faults are obstructed, thrust faults would be created to accommodate the deformation transfered by the strike slip faults. Longmenshan fault on which the Wenchuan earthquake occurred, is one of the thrust fault that accommodate the deformation transfered by the East Kunlun fault. Along the East Kunlun fault there were several large earthquakes occurred in last century. Field investigation shows that the surface ruptures created by these large earthquakes have gone through the whole East Kunlun fault, which means that the East Knulun fault could not hold up the deformation any longer, and all the burden were transfered to Longmenshan fault. This might be the reason of the occurrence of Wenchuan earthquake. November 11-14, 2008 Boulder, Colorado, USA THANK YOU FOR YOUR ATTENTION 东大滩谷地北侧发育的叠瓦状构造