Based on field geological survey, structural measurements and classical Ar/Ar dating of mica, biotite and K-feldspar, we obtain cooling ages for Miocene left-lateral shear along the Xianshuihe fault zone. The results ...Based on field geological survey, structural measurements and classical Ar/Ar dating of mica, biotite and K-feldspar, we obtain cooling ages for Miocene left-lateral shear along the Xianshuihe fault zone. The results document two thermal events during the sinistral shear. The early event (12-10 Ma) corresponds to rapid cooling of the Zheduoshan granitic massif from above 700℃ to below 350℃. The late event (5-3.5 Ma) corresponds to cooling of granites intruded along the eastern side of the fault zone. These dating results provide important thermochronological constraint on the timing of late Cenozoic eastward extrusion of the Chuan-Dian Block in the SE Tibetan margin.展开更多
Transient pore pressure in response to short intense rainfall process plays an important role in shallow landslide occurrence. Using GIS technology, we carry out the rainfall-induced landslide stability analysis in re...Transient pore pressure in response to short intense rainfall process plays an important role in shallow landslide occurrence. Using GIS technology, we carry out the rainfall-induced landslide stability analysis in response to transient pore pressure by means of transient and unsaturated rainfall infiltration modeling. A case study is performed on the shallow landslide stability analysis in Hong Kong. Detailed analysis and discussion reached some useful conclusions on the tempo-spatial behavior and characteristics of slope stability response and pore pressure response to typical rainfall process. Comparison analysis is performed on some important issues including landslide stability response in different types of slopes with different hydraulic properties, antecedent rainfall and landslide stability, and the nature of pore pressure response time. These studies might give us an important insight into landslide tringgering mechanism and the hydrological process in response to rainfall, and provide systematic information and evidences for effective risk assessment and warning system establishment.展开更多
Environmental change signals in geological or biological records are commonly reflected on their reflecting or transmitting images. These environmental signals can be extracted through digital image analysis. The anal...Environmental change signals in geological or biological records are commonly reflected on their reflecting or transmitting images. These environmental signals can be extracted through digital image analysis. The analysis principle involves section line selection, color value reading and calculating environmental proxy index along the section lines, layer identification, auto-chronology and investigation of structure evolution of growth bands. On detailed illustrations of the image technique, this note provides image analyzing procedures of coral, tree-ring and stalagmite records. The environmental implications of the proxy index from image analysis are accordingly given through application demonstration of the image technique.展开更多
We use the Pg seismic phase along the Korla-Jimsar profile across the Tianshan orogen and the 3D finite difference method to inverse the velocity structure of the upper crust beneath the basement of this mountain. Bas...We use the Pg seismic phase along the Korla-Jimsar profile across the Tianshan orogen and the 3D finite difference method to inverse the velocity structure of the upper crust beneath the basement of this mountain. Based on the velocity structure, the Korla-Jimsar profile can be divided into three parts, i.e. the north edge of the Tarim basin, the Tianshan orogen, and the south margin of the Junggar basin. Within the Tianshan there is a pattern of four convexities and three concavities, which correspond to the southern Tianshan, the Yanqi basin, the middle Tianshan, the Turpan basin, and the Bogda Mountains. In the north edge of the Tarim basin, the basement is about 10km deep with small lateral variations of velocity. In the Tianshan the velocity varies greatly laterally. The basement depth of the Yanqi basin is 6 km, which becomes shallow rapidly northward, and almost to the surface at the middle Tianshan. South to Kumux there is a small intermountain basin, where the maximum basement depth is 3 km, and also turns very shallow near Kumux. The Luntai fault, which bounds the Tarim basin and Tianshan, has vertical dislocation of about 5 km. The Turpan basin is covered with so thick a sediment that its basement is 7 km deep. The boundary fault between the Tianshan and Turpan is the Bolohoro fault which is characterized by quick deepening basement and 7 km vertical dislocation. In the Junggar basin the basement is 8 km deep. On the Korla-Jimsar profile, the velocity distribution of the upper crust and the structure are featured by NS symmetry on both sides of the axis of the Middle Tianshan, consistent with the deep structure revealed by this profile. It means that the Tarim ba-sin and the Junggar basin underthrust toward the Tianshan from south and north, respectively. Such a structural style is different from that of another profile, i.e. the Xayar-Burjing profile, sug-gesting that there may be an important tectonic boundary between these two profiles.展开更多
文摘Based on field geological survey, structural measurements and classical Ar/Ar dating of mica, biotite and K-feldspar, we obtain cooling ages for Miocene left-lateral shear along the Xianshuihe fault zone. The results document two thermal events during the sinistral shear. The early event (12-10 Ma) corresponds to rapid cooling of the Zheduoshan granitic massif from above 700℃ to below 350℃. The late event (5-3.5 Ma) corresponds to cooling of granites intruded along the eastern side of the fault zone. These dating results provide important thermochronological constraint on the timing of late Cenozoic eastward extrusion of the Chuan-Dian Block in the SE Tibetan margin.
基金This work was supported by the Council of the Hong Kong Special Administrative Region, China (Grant No. HKU 7015/02E) the National Natural Science Foundation of China (Grant No. 40225004)Postdoctoral Science Foundation of China.
文摘Transient pore pressure in response to short intense rainfall process plays an important role in shallow landslide occurrence. Using GIS technology, we carry out the rainfall-induced landslide stability analysis in response to transient pore pressure by means of transient and unsaturated rainfall infiltration modeling. A case study is performed on the shallow landslide stability analysis in Hong Kong. Detailed analysis and discussion reached some useful conclusions on the tempo-spatial behavior and characteristics of slope stability response and pore pressure response to typical rainfall process. Comparison analysis is performed on some important issues including landslide stability response in different types of slopes with different hydraulic properties, antecedent rainfall and landslide stability, and the nature of pore pressure response time. These studies might give us an important insight into landslide tringgering mechanism and the hydrological process in response to rainfall, and provide systematic information and evidences for effective risk assessment and warning system establishment.
基金This work was supported by the Knowledge Innovation Project of South China Insitute of Oceanology (Grant No. 5210607)Knowledge Innovation Project of the Chinese Academy of Sciences (Grant No. KZCX2-108)the National Natural Science Foundation of C
文摘Environmental change signals in geological or biological records are commonly reflected on their reflecting or transmitting images. These environmental signals can be extracted through digital image analysis. The analysis principle involves section line selection, color value reading and calculating environmental proxy index along the section lines, layer identification, auto-chronology and investigation of structure evolution of growth bands. On detailed illustrations of the image technique, this note provides image analyzing procedures of coral, tree-ring and stalagmite records. The environmental implications of the proxy index from image analysis are accordingly given through application demonstration of the image technique.
文摘We use the Pg seismic phase along the Korla-Jimsar profile across the Tianshan orogen and the 3D finite difference method to inverse the velocity structure of the upper crust beneath the basement of this mountain. Based on the velocity structure, the Korla-Jimsar profile can be divided into three parts, i.e. the north edge of the Tarim basin, the Tianshan orogen, and the south margin of the Junggar basin. Within the Tianshan there is a pattern of four convexities and three concavities, which correspond to the southern Tianshan, the Yanqi basin, the middle Tianshan, the Turpan basin, and the Bogda Mountains. In the north edge of the Tarim basin, the basement is about 10km deep with small lateral variations of velocity. In the Tianshan the velocity varies greatly laterally. The basement depth of the Yanqi basin is 6 km, which becomes shallow rapidly northward, and almost to the surface at the middle Tianshan. South to Kumux there is a small intermountain basin, where the maximum basement depth is 3 km, and also turns very shallow near Kumux. The Luntai fault, which bounds the Tarim basin and Tianshan, has vertical dislocation of about 5 km. The Turpan basin is covered with so thick a sediment that its basement is 7 km deep. The boundary fault between the Tianshan and Turpan is the Bolohoro fault which is characterized by quick deepening basement and 7 km vertical dislocation. In the Junggar basin the basement is 8 km deep. On the Korla-Jimsar profile, the velocity distribution of the upper crust and the structure are featured by NS symmetry on both sides of the axis of the Middle Tianshan, consistent with the deep structure revealed by this profile. It means that the Tarim ba-sin and the Junggar basin underthrust toward the Tianshan from south and north, respectively. Such a structural style is different from that of another profile, i.e. the Xayar-Burjing profile, sug-gesting that there may be an important tectonic boundary between these two profiles.
