We simulate GPS horizontal velocity field in terms of rotations of crustal blocks to describe deformation behavior of the Chinese mainland and its neighboring areas. 31 crustal blocks are bounded primarily by -30 Quat...We simulate GPS horizontal velocity field in terms of rotations of crustal blocks to describe deformation behavior of the Chinese mainland and its neighboring areas. 31 crustal blocks are bounded primarily by -30 Quaternary faults with distinct geometries and variable long-term rates of 〈20 mm/a, and 1 683 GPS velocities were determined from decade-long observations mostly with an averaged uncertainty of 1-2 mm/a. We define GPS velocity at a site by the combination of motion of rigid block and elastic strain induced by the fault that is locking during a seismic cycle. Model velocities predicted from the preferable block model match well with the GPS velocities to an uncertainty of-l.7mm/a. The slip rates inferred from this model is in a range of 6-18 mm/a for the major faults in Tibet and its margins and 1-4 mm/a in eastern China, consistent with geological observations. Our numerical simulation suggests that the crustal blocks deform internally at a level of-10× 10^-9/a, quite small in comparison with significant deformation localized along fault zones of 50-100 km wide. We conclude that the pattern of continental deformation is not continuous-like but block-like, and the tenet of plate tectonics may be applicable to characterize the active deformation in Asia.展开更多
Metasediments from the Tethyan Himalaya (TH) were sampled for paleomagnetic studies in several areas. In this paper, we will present the first results from Carboniferous and Early Triassic marly limestones from Hidden...Metasediments from the Tethyan Himalaya (TH) were sampled for paleomagnetic studies in several areas. In this paper, we will present the first results from Carboniferous and Early Triassic marly limestones from Hidden Valley (Central Nepal).. The paleomagnetic directions reflect a Tertiary overprint probably synchronous with the metamorphism. In this area, the metamorphic conditions reached during Tertiary are poorly constrained. Temperatures are probably in between 300 and 400℃. The age of the thermal event is still debated. No geochronological data is available in this area. Previously published geochronological data from the northern part of TH metasediments in India ranges from 47 to 42Ma (Ar/Ar Illite) after Weissman et al. (1999) and Bonhomme and Garzanti (1991). While in the southern part (close to HHC), biotite Ar/Ar data ranges from 30 to 26Ma in Marsyandi Valley (Coleman and Hodges, 1998) and muscovite Ar/Ar ranges from 18 to 12Ma in the upper Kali Gandaki Valley (Godin et al., 1998).. In this context, the age of the magnetization can′t be defined with precision.展开更多
Objective The lateral extrusion of southeastern edge of the crustal materials around the Tibetan Plateau since the Oligocene is believed to be one of the main inducements of-1300 km latitudinal crustal convergence in...Objective The lateral extrusion of southeastern edge of the crustal materials around the Tibetan Plateau since the Oligocene is believed to be one of the main inducements of-1300 km latitudinal crustal convergence in the Tibetan Plateau, since the collision of India and Eurasia in the Paleogene. Two end-member models were used to describe the process of lateral extrusion of crustal material on the southeastern edge of the Tibetan Plateau. The ＂tectonic escape＂ model suggests the Indochina Block, Chuandian Fragment and Shan-Thai Block have experienced lateral extrusion along strike-slip fault systems, and the ＂crustal flow＂ model suggests that the upper crust has undergone southeastward escape in the form of ductile deformation, driven by viscous lower crustal flow channels. In addition, the GPS observations surrounding the Tibetan Plateau indicate that crustal materials currently experience clockwise rotation around the Eastern Himalaya syntaxis. This work conducted paleomagnetic studies in the Cretaceous and Paleogene red-beds along the southeastern margin of Tibetan Plateau,展开更多
基金supported bythe National Natural Science Foundation of China(No.40674054,40774014 and 40974012)Foundation of Institute of Seismology CEA(IS200856059)
文摘We simulate GPS horizontal velocity field in terms of rotations of crustal blocks to describe deformation behavior of the Chinese mainland and its neighboring areas. 31 crustal blocks are bounded primarily by -30 Quaternary faults with distinct geometries and variable long-term rates of 〈20 mm/a, and 1 683 GPS velocities were determined from decade-long observations mostly with an averaged uncertainty of 1-2 mm/a. We define GPS velocity at a site by the combination of motion of rigid block and elastic strain induced by the fault that is locking during a seismic cycle. Model velocities predicted from the preferable block model match well with the GPS velocities to an uncertainty of-l.7mm/a. The slip rates inferred from this model is in a range of 6-18 mm/a for the major faults in Tibet and its margins and 1-4 mm/a in eastern China, consistent with geological observations. Our numerical simulation suggests that the crustal blocks deform internally at a level of-10× 10^-9/a, quite small in comparison with significant deformation localized along fault zones of 50-100 km wide. We conclude that the pattern of continental deformation is not continuous-like but block-like, and the tenet of plate tectonics may be applicable to characterize the active deformation in Asia.
文摘Metasediments from the Tethyan Himalaya (TH) were sampled for paleomagnetic studies in several areas. In this paper, we will present the first results from Carboniferous and Early Triassic marly limestones from Hidden Valley (Central Nepal).. The paleomagnetic directions reflect a Tertiary overprint probably synchronous with the metamorphism. In this area, the metamorphic conditions reached during Tertiary are poorly constrained. Temperatures are probably in between 300 and 400℃. The age of the thermal event is still debated. No geochronological data is available in this area. Previously published geochronological data from the northern part of TH metasediments in India ranges from 47 to 42Ma (Ar/Ar Illite) after Weissman et al. (1999) and Bonhomme and Garzanti (1991). While in the southern part (close to HHC), biotite Ar/Ar data ranges from 30 to 26Ma in Marsyandi Valley (Coleman and Hodges, 1998) and muscovite Ar/Ar ranges from 18 to 12Ma in the upper Kali Gandaki Valley (Godin et al., 1998).. In this context, the age of the magnetization can′t be defined with precision.
基金supported by the National Natural Science Foundation of China(grants No.41202162 and 41572183)
文摘Objective The lateral extrusion of southeastern edge of the crustal materials around the Tibetan Plateau since the Oligocene is believed to be one of the main inducements of-1300 km latitudinal crustal convergence in the Tibetan Plateau, since the collision of India and Eurasia in the Paleogene. Two end-member models were used to describe the process of lateral extrusion of crustal material on the southeastern edge of the Tibetan Plateau. The ＂tectonic escape＂ model suggests the Indochina Block, Chuandian Fragment and Shan-Thai Block have experienced lateral extrusion along strike-slip fault systems, and the ＂crustal flow＂ model suggests that the upper crust has undergone southeastward escape in the form of ductile deformation, driven by viscous lower crustal flow channels. In addition, the GPS observations surrounding the Tibetan Plateau indicate that crustal materials currently experience clockwise rotation around the Eastern Himalaya syntaxis. This work conducted paleomagnetic studies in the Cretaceous and Paleogene red-beds along the southeastern margin of Tibetan Plateau,
