The Liquine-Ofqui Fault Zone(LOFZ) of southern Chilean Andes is one of the largest active strike-slip fault zones.There is an ongoing debate regarding the origin of the stress field along the LOFZ due to its complex g...The Liquine-Ofqui Fault Zone(LOFZ) of southern Chilean Andes is one of the largest active strike-slip fault zones.There is an ongoing debate regarding the origin of the stress field along the LOFZ due to its complex geometry.This paper represents a study of the origins of the LOFZ regional stress field.Stress fields are calculated by finite element(FE) analysis.The two possible stress origins, i.e., oblique plate convergence and ridge collision/indenter tectonics of Chile ridge against Peru-Chile trench, have been emphasized in the present study.Three types of boundary conditions for the three particular models have been applied to calculate stress fields.Models are assumed to be elastic and plane stress condition.Modeling results are presented in terms of four parameters, i.e., orientation of maximum horizontal stress(σ H max ), displacement vector, s train distribution, and maximum shear stress(τmax ) contour line within the model.The results of the first model with oblique plate convergence show inconsistency between the geometric shape of the LOFZ and the distribution of the four parameters.Although more realistic results are obtained from the second model with normal ridge collision, there are few coincident in the LOFZ geometry and regional stress field.The third model with normal and oblique ridge collision is reasonable in understanding the origin of stress field and geometrical condition in the lithosphere of the LOFZ.展开更多
The Lhasa-Gangdise Terrane is taken as a representative mobile terrane during the Himalayan orogeny of the India- Eurasia continental collision, for which a corresponding kinematics-uplift model is set up. The paramet...The Lhasa-Gangdise Terrane is taken as a representative mobile terrane during the Himalayan orogeny of the India- Eurasia continental collision, for which a corresponding kinematics-uplift model is set up. The parameterization of the model is ultimately constrained by the uplift history outlined by synthesized paleogeoglaphic studies with consideration of the following factors: (1 ) kinematic features of india-Eurasia plate convergence; (2) 3-D mass conservation during terrane deformations incorporating shortening, thickening, extension, uplift and ero sion; and (3) instantaneous vertical movement of lithospheric material under the control of isostasy. The model study involves the following four groups of uplift-relevant parameters: ① plate converging velocity and its variations with time; ② extent of lateral mass transfer; ③ crustal structure: and ④) surface erosion mode. The results of calculation of 144 models of different Parameter combinations have indicated the non-uniqueness of solution. Nevertheless, it is also proved that for a fixed kinematic mode of plate convergence there exists a unique best-fitting model which may reproduce the observed uplift history, implying the uniqueness of dynamic environment of two converging plates. Therefore, the uplift of the Himalayan-Tibetan region is mainly controlled by plate dynamics-kinematics and is a complicated geological process of far-reaching implications.展开更多
文摘The Liquine-Ofqui Fault Zone(LOFZ) of southern Chilean Andes is one of the largest active strike-slip fault zones.There is an ongoing debate regarding the origin of the stress field along the LOFZ due to its complex geometry.This paper represents a study of the origins of the LOFZ regional stress field.Stress fields are calculated by finite element(FE) analysis.The two possible stress origins, i.e., oblique plate convergence and ridge collision/indenter tectonics of Chile ridge against Peru-Chile trench, have been emphasized in the present study.Three types of boundary conditions for the three particular models have been applied to calculate stress fields.Models are assumed to be elastic and plane stress condition.Modeling results are presented in terms of four parameters, i.e., orientation of maximum horizontal stress(σ H max ), displacement vector, s train distribution, and maximum shear stress(τmax ) contour line within the model.The results of the first model with oblique plate convergence show inconsistency between the geometric shape of the LOFZ and the distribution of the four parameters.Although more realistic results are obtained from the second model with normal ridge collision, there are few coincident in the LOFZ geometry and regional stress field.The third model with normal and oblique ridge collision is reasonable in understanding the origin of stress field and geometrical condition in the lithosphere of the LOFZ.
文摘The Lhasa-Gangdise Terrane is taken as a representative mobile terrane during the Himalayan orogeny of the India- Eurasia continental collision, for which a corresponding kinematics-uplift model is set up. The parameterization of the model is ultimately constrained by the uplift history outlined by synthesized paleogeoglaphic studies with consideration of the following factors: (1 ) kinematic features of india-Eurasia plate convergence; (2) 3-D mass conservation during terrane deformations incorporating shortening, thickening, extension, uplift and ero sion; and (3) instantaneous vertical movement of lithospheric material under the control of isostasy. The model study involves the following four groups of uplift-relevant parameters: ① plate converging velocity and its variations with time; ② extent of lateral mass transfer; ③ crustal structure: and ④) surface erosion mode. The results of calculation of 144 models of different Parameter combinations have indicated the non-uniqueness of solution. Nevertheless, it is also proved that for a fixed kinematic mode of plate convergence there exists a unique best-fitting model which may reproduce the observed uplift history, implying the uniqueness of dynamic environment of two converging plates. Therefore, the uplift of the Himalayan-Tibetan region is mainly controlled by plate dynamics-kinematics and is a complicated geological process of far-reaching implications.
