The focal mechanisms of 32 earthquakes with magnitude of M_S≥3.0, which were recorded by the Guangdong Digital Seismographic Network, are calculated by using P-wave polarity and amplitude ratio data, and those of 83 ...The focal mechanisms of 32 earthquakes with magnitude of M_S≥3.0, which were recorded by the Guangdong Digital Seismographic Network, are calculated by using P-wave polarity and amplitude ratio data, and those of 83 earthquakes of Guangdong and its adjacent areas derived by previous researchers are sorted out. On the basis of this, the characteristics of focal mechanism in Guangdong and its adjacent areas are summarized. Meanwhile the focal mechanisms of three earthquake areas, i.e., Yangjiang, Xinfengjiang and Nanao, are discussed respectively. Results show clear regional feature in the function and nature of the stress, and earthquakes are mostly of strike-slip associated with dip-slip component. Earthquakes in the Xinfengjiang Reservoir area are all reservoir-induced ones, so they are only of strike-slip and normal faulting types. In the Yangjiang area, some thrust earthquakes occurred. The dominant orientation of principal compressive stress axis changes from NS in Hainan, Gaungxi to NWW in Guangdong and finally near EW in the coastal areas of Guangdong and Fujian Provinces.展开更多
China＇s new urbanization process requires coordinated development between cities and rural areas. Territorial functions of rural areas are defined as advantageous effects on nature and human society that, in particul...China＇s new urbanization process requires coordinated development between cities and rural areas. Territorial functions of rural areas are defined as advantageous effects on nature and human society that, in particular, rural systems perform via their property and interactions with other systems at certain social development stages. This paper establishes an index System for evaluating rural territorial functions including agricultural function, social function, economic function and ecological function. By establishing a model based on a General Regression Neural Network （GRNN） with the county-level as the basic unit, we comprehensively evaluate the rural territorial functions of 109 counties and/or cities in Henan province, China in 2000, 2005 and 2010. Results show that compared with that in 2000, each function in 2010 improved, with the spatial heterogeneity of economic func- tion the most evident, social service function comparatively balanced and spatial distribution of agricultural produc- tion function changing little. Cluster analysis was adopted to study the major functions of rural regions. Henan was divided into six major function zones to enhance administrative management and developmental policy. The six major function zones are Type I （core economic development zone）, Type II （agricultural production safeguarding zone）, Type III （function improving zone for rural areas）, Type IV （model zone of livelihood and social services）, Type V （economic restructuring and development zone）, and Type Vl （nature conservation areas）. Different development goals and development strategies should be considered according to different major function areas to achieve the coordinated development of urban and rural areas in China.展开更多
The crustal structure of the northwestern sub-basin area of the South China Sea was modeled by inverting a wide-angle seismic survey line across the entire region and on both sides of its bounding continental margins....The crustal structure of the northwestern sub-basin area of the South China Sea was modeled by inverting a wide-angle seismic survey line across the entire region and on both sides of its bounding continental margins. The survey line extended over 484 km. A total of 14 Ocean Bottom Seismometers (OBS) were deployed at intervals of 30 km to record air-gun array sources with a combined volume of 5160 in 3 . The crustal velocity structure of the northwestern sub-basin area was acquired through the integration of multi-channel seismic data. OBS data were processed and modeled initially using ray tracing inversion techniques. Results indicate that crustal thickness under the continental slope decreases from 21 to 11 km, crustal thickness of the northwestern sub-basin is 7.7 km, and the depth to the Moho ascends from 21 km under the upper continental slope to 11 km under the middle basin. The crust of the northwestern sub-basin is similar to that of the eastern sub-basin in its oceanic crustal structure. This structure has a thicker layer 1 (sedimentary layer) and a thinner layer 2. These characteristics are especially clear in the eastern sub-basin, which differs somewhat from typical oceanic crust. The tectonic geometry and velocity structure of the northwestern sub-basin and its margins comprise a symmetrical conjugate and indicate a pure shear mode with regard to the continental margin rifting mechanism. We did not find clear seismic signals from high velocity layers under the lower crust of the continental margin in the northern part of the northwestern sub-basin, which provides new evidence for the idea that the western part of the northern continental margin of the South China Sea constitutes nonvolcanic crust. Because the seafloor spreading period of the northwestern sub-basin was short, layer 2 might have experienced asymmetrical basalt magma flows, which may have blurred the magnetic anomaly lineations of the northwestern sub-basin.展开更多
文摘The focal mechanisms of 32 earthquakes with magnitude of M_S≥3.0, which were recorded by the Guangdong Digital Seismographic Network, are calculated by using P-wave polarity and amplitude ratio data, and those of 83 earthquakes of Guangdong and its adjacent areas derived by previous researchers are sorted out. On the basis of this, the characteristics of focal mechanism in Guangdong and its adjacent areas are summarized. Meanwhile the focal mechanisms of three earthquake areas, i.e., Yangjiang, Xinfengjiang and Nanao, are discussed respectively. Results show clear regional feature in the function and nature of the stress, and earthquakes are mostly of strike-slip associated with dip-slip component. Earthquakes in the Xinfengjiang Reservoir area are all reservoir-induced ones, so they are only of strike-slip and normal faulting types. In the Yangjiang area, some thrust earthquakes occurred. The dominant orientation of principal compressive stress axis changes from NS in Hainan, Gaungxi to NWW in Guangdong and finally near EW in the coastal areas of Guangdong and Fujian Provinces.
基金National Natural Science Foundation of China(41571096)
文摘China＇s new urbanization process requires coordinated development between cities and rural areas. Territorial functions of rural areas are defined as advantageous effects on nature and human society that, in particular, rural systems perform via their property and interactions with other systems at certain social development stages. This paper establishes an index System for evaluating rural territorial functions including agricultural function, social function, economic function and ecological function. By establishing a model based on a General Regression Neural Network （GRNN） with the county-level as the basic unit, we comprehensively evaluate the rural territorial functions of 109 counties and/or cities in Henan province, China in 2000, 2005 and 2010. Results show that compared with that in 2000, each function in 2010 improved, with the spatial heterogeneity of economic func- tion the most evident, social service function comparatively balanced and spatial distribution of agricultural produc- tion function changing little. Cluster analysis was adopted to study the major functions of rural regions. Henan was divided into six major function zones to enhance administrative management and developmental policy. The six major function zones are Type I （core economic development zone）, Type II （agricultural production safeguarding zone）, Type III （function improving zone for rural areas）, Type IV （model zone of livelihood and social services）, Type V （economic restructuring and development zone）, and Type Vl （nature conservation areas）. Different development goals and development strategies should be considered according to different major function areas to achieve the coordinated development of urban and rural areas in China.
基金supported by National Basic Research Program of China (Grant No. 2007CB411701)National Natural Science Foundation of China (Grant Nos. 40876035 and 91028006)Scientific Research Fund of the Second Institute of Oceanography, State Oceanic Administration (Grant No. JG200803)
文摘The crustal structure of the northwestern sub-basin area of the South China Sea was modeled by inverting a wide-angle seismic survey line across the entire region and on both sides of its bounding continental margins. The survey line extended over 484 km. A total of 14 Ocean Bottom Seismometers (OBS) were deployed at intervals of 30 km to record air-gun array sources with a combined volume of 5160 in 3 . The crustal velocity structure of the northwestern sub-basin area was acquired through the integration of multi-channel seismic data. OBS data were processed and modeled initially using ray tracing inversion techniques. Results indicate that crustal thickness under the continental slope decreases from 21 to 11 km, crustal thickness of the northwestern sub-basin is 7.7 km, and the depth to the Moho ascends from 21 km under the upper continental slope to 11 km under the middle basin. The crust of the northwestern sub-basin is similar to that of the eastern sub-basin in its oceanic crustal structure. This structure has a thicker layer 1 (sedimentary layer) and a thinner layer 2. These characteristics are especially clear in the eastern sub-basin, which differs somewhat from typical oceanic crust. The tectonic geometry and velocity structure of the northwestern sub-basin and its margins comprise a symmetrical conjugate and indicate a pure shear mode with regard to the continental margin rifting mechanism. We did not find clear seismic signals from high velocity layers under the lower crust of the continental margin in the northern part of the northwestern sub-basin, which provides new evidence for the idea that the western part of the northern continental margin of the South China Sea constitutes nonvolcanic crust. Because the seafloor spreading period of the northwestern sub-basin was short, layer 2 might have experienced asymmetrical basalt magma flows, which may have blurred the magnetic anomaly lineations of the northwestern sub-basin.
