Longmen Shan is located the special joint between the Qinghai-Tibetan Plateau in the west and the Yangtze craton in the east. Consisting of a series of parallel imbricated thrust, it develops, from the west to the eas...Longmen Shan is located the special joint between the Qinghai-Tibetan Plateau in the west and the Yangtze craton in the east. Consisting of a series of parallel imbricated thrust, it develops, from the west to the east, the Maoxian-Wenchuan, Yingxiu-Beichuan and Pengxian-Guanxian faults. Wenchuan Ms 8.0 earthquake is a thrust with strike-slip type, and surface ruptures are located in Yingxiu-Beichuan fault zone and Peng- xian-Guanxian fault zone. Based on the geological background, tectonic setting, the active tectonics of Long- men Shan and surface ruptures of the Wenchuan earthquake, a dynamical model to illustrate possible links between surface processes and upward extrusion of lower crustal flow channel at the eastern margin of the Tibetan plateau have been studied, and the results is the material in lower crust in the Longmen Shan moving as nearly-vertical extrusion and uplift, resulting in the surface rate of tectonic movement differing according to depth rate as well as the occurrence of large shallow Wenchuan earthquake.展开更多
The Litang fault is a left-lateral secondary shear zone in the Sichuan-Yunnan active block that accommodates the tectonic deformation associated with the eastward extrusion of the upper crust of the Tibetan Plateau. B...The Litang fault is a left-lateral secondary shear zone in the Sichuan-Yunnan active block that accommodates the tectonic deformation associated with the eastward extrusion of the upper crust of the Tibetan Plateau. Based on 1 : 50 000 geological mapping of active faults, the Litang fault consists of three geometric segments, the Cuopuhu, Damaoyaba, and Litang segments, in the west of Litang, which are divided by the of Haizi Mountain uplift and the wide-angle bending and branching of the fault near Jinchanggou. This study also identifies the surface rupture of the A.D. 1890 earthquake, which is distributed intermittently along the ~28 km long Damaoyaba segments and ~25 km long Litang segments. The maximum horizontal displacement is 4.1 m along Damaoyaba segments, and 4 m along Litang segments. The rupture involves typical left-lateral shear movement. The two ruptures are divided by discontinuous segments or gaps that are ~18 km long;thus, the total surface rupture is approximately 71 km long. The estimated moment magnitude was M_(w)7.3±0.1. A comprehensive analysis of data obtained from 5 trenches excavated along the Damaoyaba and Litang segments and the trench data by Xu et al.(2005) identifies age constraints of the 4 most recent paleoseimic events occurred B.C. 1468±54–1340±25, B.C. 52±25–A.D. 76±47, A.D. 1115±90, and A.D. 1890, respectively. The recurrence intervals are 1 415±80, 1 104±104, and 775±90 a, which are consistent with quasi-periodic earthquake recurrence behavior. The average recurrence interval is 1 098±112 a.展开更多
文摘Longmen Shan is located the special joint between the Qinghai-Tibetan Plateau in the west and the Yangtze craton in the east. Consisting of a series of parallel imbricated thrust, it develops, from the west to the east, the Maoxian-Wenchuan, Yingxiu-Beichuan and Pengxian-Guanxian faults. Wenchuan Ms 8.0 earthquake is a thrust with strike-slip type, and surface ruptures are located in Yingxiu-Beichuan fault zone and Peng- xian-Guanxian fault zone. Based on the geological background, tectonic setting, the active tectonics of Long- men Shan and surface ruptures of the Wenchuan earthquake, a dynamical model to illustrate possible links between surface processes and upward extrusion of lower crustal flow channel at the eastern margin of the Tibetan plateau have been studied, and the results is the material in lower crust in the Longmen Shan moving as nearly-vertical extrusion and uplift, resulting in the surface rate of tectonic movement differing according to depth rate as well as the occurrence of large shallow Wenchuan earthquake.
基金This research was supported by the“China Seismic Active Fault Exploration,Central-South Segment Project of the NorthSouth Seismic Belt”of the China Earthquake Administrationthe National Science Foundation of China(No.41372114)。
文摘The Litang fault is a left-lateral secondary shear zone in the Sichuan-Yunnan active block that accommodates the tectonic deformation associated with the eastward extrusion of the upper crust of the Tibetan Plateau. Based on 1 : 50 000 geological mapping of active faults, the Litang fault consists of three geometric segments, the Cuopuhu, Damaoyaba, and Litang segments, in the west of Litang, which are divided by the of Haizi Mountain uplift and the wide-angle bending and branching of the fault near Jinchanggou. This study also identifies the surface rupture of the A.D. 1890 earthquake, which is distributed intermittently along the ~28 km long Damaoyaba segments and ~25 km long Litang segments. The maximum horizontal displacement is 4.1 m along Damaoyaba segments, and 4 m along Litang segments. The rupture involves typical left-lateral shear movement. The two ruptures are divided by discontinuous segments or gaps that are ~18 km long;thus, the total surface rupture is approximately 71 km long. The estimated moment magnitude was M_(w)7.3±0.1. A comprehensive analysis of data obtained from 5 trenches excavated along the Damaoyaba and Litang segments and the trench data by Xu et al.(2005) identifies age constraints of the 4 most recent paleoseimic events occurred B.C. 1468±54–1340±25, B.C. 52±25–A.D. 76±47, A.D. 1115±90, and A.D. 1890, respectively. The recurrence intervals are 1 415±80, 1 104±104, and 775±90 a, which are consistent with quasi-periodic earthquake recurrence behavior. The average recurrence interval is 1 098±112 a.
