On 12th May 2008, a MW7.9 earthquake occurred on the Longmenshan fault in the mountains to the west of Sichuan Province, which shook many Asian cities and killed at least 69000 people. The surface ruptures strike NE a...On 12th May 2008, a MW7.9 earthquake occurred on the Longmenshan fault in the mountains to the west of Sichuan Province, which shook many Asian cities and killed at least 69000 people. The surface ruptures strike NE and extend up to 270 km along the boundary between the eastern Tibetan Plateau and the Sichuan basin. It was difficult to complete the detailed mapping of surface ruptures and to measure fault slip in the field because well-defined features to correlate across the fault were rare in mountainous area. Near surface deformation is in fact composed of contributions from internal faulting and folding. Using the COSI-Corr software, we obtain coseismic ground displacements deduced from sub-pixel correlation of SPOT5 and ENVISAT and also from D-InSAR on ENVISAT. The results can provide continuous surface displacements. In the south, the results show significant shortening, generally <10 meters, and two parallel ruptures, while in the north, they show strike slip dominant and only a single rupture. Based on our results, we simulate the fault geometry in different locations. To realize the long-term fault kinematics a comparison is further needed between coseismic deformation and long-term geomorphic deformation recorded in the landforms.展开更多
The Chi-Chi earthquake, after 10 years of study, is arguably the one of the best constrained and best studied large thrust-belt earthquake worldwide, considered from a number of perspectives, including geophysical ins...The Chi-Chi earthquake, after 10 years of study, is arguably the one of the best constrained and best studied large thrust-belt earthquake worldwide, considered from a number of perspectives, including geophysical instrumentation, strong ground-motion records, geodetic constraints on surface displacements, post-earthquake borehole data and surface geologic studies. In addition it is arguably the geologically best constrained earthquake from the point of view of independent constraints on the 3D subsurface structural geometry of the Chelungpu and related faults that slipped in the earthquake, as well as the deeper tectonic structure of Taiwan that feeds lithospheric convergence into the Chelungpu fault system. These insights from the Chi-Chi earthquake may give us some ideas for study of the structural geology of the Wenchuan earthquake. Both are thrust-belt earthquakes, but the Wenchuan is in a more interior and more complex position, making it more challenging to study. Here we present the 3-D structural geometry of the key faults in the Chi-Chi earthquake and show how they are related to the coseismic surface and fault displacements. We then make comparisons to the coseismic displacements in the Wenchuan earthquake and their relationship to structural展开更多
The past size and location of the hypothesized proto-South China Sea vanished ocean basin has important plate-tectonic implications for Southeast Asia since the Mesozoic. Here we present new details on proto-South Chi...The past size and location of the hypothesized proto-South China Sea vanished ocean basin has important plate-tectonic implications for Southeast Asia since the Mesozoic. Here we present new details on proto-South China Sea paleogeography using mapped and unfolded slabs from tomography. Mapped slabs included: the Eurasia-South China Sea slab subducting at the Manila trench; the northern Philippine Sea Plate slab subducting at the Ryukyu trench; and, a swath of detached, subhorizontal, slab-like tomographic anomalies directly under the South China Sea at 450 to 700 km depths that we show is subducted ‘northern proto-South China Sea' lithosphere. Slab unfolding revealed that the South China Sea lay directly above the ‘northern Proto-South China Sea' with both extending 400 to 500 km to the east of the present Manila trench prior to subduction. Our slab-based plate reconstruction indicated the proto-South China Sea was consumed by double-sided subduction, as follows:(1) The ‘northern proto-South China Sea' subducted in the Oligo–Miocene under the Dangerous Grounds and southward expanding South China Sea by in-place ‘self subduction' similar to the western Mediterranean basins;(2) limited southward subduction of the proto-South China Sea under Borneo occurred pre-Oligocene, represented by the 800–900 km deep ‘southern proto-South China Sea' slab.展开更多
文摘On 12th May 2008, a MW7.9 earthquake occurred on the Longmenshan fault in the mountains to the west of Sichuan Province, which shook many Asian cities and killed at least 69000 people. The surface ruptures strike NE and extend up to 270 km along the boundary between the eastern Tibetan Plateau and the Sichuan basin. It was difficult to complete the detailed mapping of surface ruptures and to measure fault slip in the field because well-defined features to correlate across the fault were rare in mountainous area. Near surface deformation is in fact composed of contributions from internal faulting and folding. Using the COSI-Corr software, we obtain coseismic ground displacements deduced from sub-pixel correlation of SPOT5 and ENVISAT and also from D-InSAR on ENVISAT. The results can provide continuous surface displacements. In the south, the results show significant shortening, generally <10 meters, and two parallel ruptures, while in the north, they show strike slip dominant and only a single rupture. Based on our results, we simulate the fault geometry in different locations. To realize the long-term fault kinematics a comparison is further needed between coseismic deformation and long-term geomorphic deformation recorded in the landforms.
文摘The Chi-Chi earthquake, after 10 years of study, is arguably the one of the best constrained and best studied large thrust-belt earthquake worldwide, considered from a number of perspectives, including geophysical instrumentation, strong ground-motion records, geodetic constraints on surface displacements, post-earthquake borehole data and surface geologic studies. In addition it is arguably the geologically best constrained earthquake from the point of view of independent constraints on the 3D subsurface structural geometry of the Chelungpu and related faults that slipped in the earthquake, as well as the deeper tectonic structure of Taiwan that feeds lithospheric convergence into the Chelungpu fault system. These insights from the Chi-Chi earthquake may give us some ideas for study of the structural geology of the Wenchuan earthquake. Both are thrust-belt earthquakes, but the Wenchuan is in a more interior and more complex position, making it more challenging to study. Here we present the 3-D structural geometry of the key faults in the Chi-Chi earthquake and show how they are related to the coseismic surface and fault displacements. We then make comparisons to the coseismic displacements in the Wenchuan earthquake and their relationship to structural
文摘The past size and location of the hypothesized proto-South China Sea vanished ocean basin has important plate-tectonic implications for Southeast Asia since the Mesozoic. Here we present new details on proto-South China Sea paleogeography using mapped and unfolded slabs from tomography. Mapped slabs included: the Eurasia-South China Sea slab subducting at the Manila trench; the northern Philippine Sea Plate slab subducting at the Ryukyu trench; and, a swath of detached, subhorizontal, slab-like tomographic anomalies directly under the South China Sea at 450 to 700 km depths that we show is subducted ‘northern proto-South China Sea' lithosphere. Slab unfolding revealed that the South China Sea lay directly above the ‘northern Proto-South China Sea' with both extending 400 to 500 km to the east of the present Manila trench prior to subduction. Our slab-based plate reconstruction indicated the proto-South China Sea was consumed by double-sided subduction, as follows:(1) The ‘northern proto-South China Sea' subducted in the Oligo–Miocene under the Dangerous Grounds and southward expanding South China Sea by in-place ‘self subduction' similar to the western Mediterranean basins;(2) limited southward subduction of the proto-South China Sea under Borneo occurred pre-Oligocene, represented by the 800–900 km deep ‘southern proto-South China Sea' slab.
