Asia is the largest distribution area of salt-affected soils in the world. Very few countries in Asia couldescape from hazard of salinization. This paper deals with various salt-affected soils spreading in East Asiaan...Asia is the largest distribution area of salt-affected soils in the world. Very few countries in Asia couldescape from hazard of salinization. This paper deals with various salt-affected soils spreading in East Asiaand its neighboring regions (including China, Japan, Kampuchea, Democratic People’s Republic of Korea,Republic of Korea, Laos, Mongolia, Burma, Thailand and Vietnam). Principles of occurrence of salinization,and features of salt-affected soils in these regions have been studied in the present paper. Based on studieson types, features and distribution patterns of salt-affected soils, a salt-affected soil map of East Asia andits neighboring regions has been complied. Mechanism and manifestation of the salinization hazard on theregional agriculture and ecological environment, measures of preventing salinization hazard and exploitingsalt-affected soils in these regions are also discussed.展开更多
Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magneti...Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magnetic and drilling wells data led to the discovery of three post fault sequences (V, VI, VII). Extensive tectonic uplift, magma activity and erosion occurred in Dongsha Island and the adjacent area, where most of the faults in the northeastern SCS were still active during Pliocene and Quaternary. Two groups of faults trending NEE and NW were developed during Late Cenozoic. We conclude that three important tectonic movements, especially Dongsha movement (4.4-5.2 Ma) and Liuhua movement (1.4-1.89 Ma), controlled the structural framework in the Dongsha rise; whose deformation in the east is stronger than that in the west and whose stress field variation suggests that the tectonic uplift in the study area contributed to magmato tectonic events correlated to the main collision phases between the East China and Taiwan 5-3 and 3-0 Ma ago.展开更多
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
文摘Asia is the largest distribution area of salt-affected soils in the world. Very few countries in Asia couldescape from hazard of salinization. This paper deals with various salt-affected soils spreading in East Asiaand its neighboring regions (including China, Japan, Kampuchea, Democratic People’s Republic of Korea,Republic of Korea, Laos, Mongolia, Burma, Thailand and Vietnam). Principles of occurrence of salinization,and features of salt-affected soils in these regions have been studied in the present paper. Based on studieson types, features and distribution patterns of salt-affected soils, a salt-affected soil map of East Asia andits neighboring regions has been complied. Mechanism and manifestation of the salinization hazard on theregional agriculture and ecological environment, measures of preventing salinization hazard and exploitingsalt-affected soils in these regions are also discussed.
文摘Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magnetic and drilling wells data led to the discovery of three post fault sequences (V, VI, VII). Extensive tectonic uplift, magma activity and erosion occurred in Dongsha Island and the adjacent area, where most of the faults in the northeastern SCS were still active during Pliocene and Quaternary. Two groups of faults trending NEE and NW were developed during Late Cenozoic. We conclude that three important tectonic movements, especially Dongsha movement (4.4-5.2 Ma) and Liuhua movement (1.4-1.89 Ma), controlled the structural framework in the Dongsha rise; whose deformation in the east is stronger than that in the west and whose stress field variation suggests that the tectonic uplift in the study area contributed to magmato tectonic events correlated to the main collision phases between the East China and Taiwan 5-3 and 3-0 Ma ago.
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.
