Investigation of the deep geophysical structure of the Longmen Mountains tectonic belt and its relation to the Wenchuan Earthquake is important for the study of earthquakes.By using magnetotelluric sounding profiles o...Investigation of the deep geophysical structure of the Longmen Mountains tectonic belt and its relation to the Wenchuan Earthquake is important for the study of earthquakes.By using magnetotelluric sounding profiles of the Luqu-Zhongjiang and Anxian-Suining; seismic sounding profiles of the Sichuan Maowen-Chongqing Gongtan,the Qinghai Huashi Gorge-Sichuan Jianyang,and the Batang-Zizhong; and magnetogravimetric data of the Longmen Mountains region,the deep geophysical structure of the Songpan-Ganzi block,the western Sichuan foreland basin,and the Longmen Mountains tectonic belt and their relation was discussed.The eastward extrusion of the Qinghai-Tibet Plateau thrusts the Songpan-Ganzi block upon the Yangtze block,which obstructs the eastward movement of the Qinghai-Tibet Plateau.The Maoxian-Wenchuan,Beichuan-Yingxiu,and Anxian-Guanxian faults of the Longmen Mountains fault belt dip to northwest with different dip angles and gradually converge in the deeper parts.Geophysical structure suggests that an intracrustal low-velocity,low-resistivity,and high-conductivity layer is common between the middle and upper crust west of the Longmen Mountains tectonic belt but not in the upper Yangtze block.The Sichuan Basin has a thick low-resistance sedimentary layer on a stable high-resistance basement; moreover,there are secondary paleohighs and depression structures at the lower part of the western Sichuan foreland basin with characteristic of high magnetic anomalies,whereas the Songpan-Ganzi block has a high resisitivity cover of upper crust and continues to a low-resistance layer.Considering the Longmen Mountains tectonic belt as the boundary,there are Bouguer gravity anomalies of "one belt between two zones." Thus,we infer that there is a corresponding relation between the inferred crystalline basement of the Songpan block and the underlying basin basement of the Longmen Mountains fault belt.Furthermore,there may be an extensive ancient Yangtze block,which is west of the Ruoergai block.In addition,the crust-mantle ductile shear zone under the Longmen Mountains tectonic belt is the main fault,whereas the Beichuan-Yingxiu and Anxian-Guanxian faults at the surface are earthquake faults.The Wenchuan Ms 8.0 earthquake might be attributed to the collision of the Yangtze block and the Qinghai-Tibet Plateau.The eastward obduction of the eastern edge of the Qinghai-Tibet Plateau and eastward subduction of its deeper part under the influence of the collision of the Indian,Pacific,and Philippine Plates with the Eurasia Plate might have caused the Longmen Mountains tectonic belt to cut the Moho and extend to the middle and upper crust; thus,creating high stress concentration and rapid energy release zone.展开更多
藏波罗花Incarvillea younghusbandii是著名的藏药之一,极具开发和研究价值,但准确预测其潜在地理分布一直是目前尚未解决的关键问题。本文结合实地调查与现有研究数据,以气候和地表覆盖为环境变量,利用Maxent模型与GIS工具,对藏波罗花...藏波罗花Incarvillea younghusbandii是著名的藏药之一,极具开发和研究价值,但准确预测其潜在地理分布一直是目前尚未解决的关键问题。本文结合实地调查与现有研究数据,以气候和地表覆盖为环境变量,利用Maxent模型与GIS工具,对藏波罗花在西藏地区的潜在地理分布进行预测。研究结果表明:(1)Maxent模型对藏波罗花的潜在地理分布具有较高的预测精度,ROC曲线下面积(Area under the curve,AUC),训练AUC值可达0.994,测试AUC值可达0.996;(2)土壤类型、年降水量和生长繁育期降水量是影响藏波罗花生长分布的最重要环境因子;(3)藏波罗花在西藏有广泛的适生性,雅鲁藏布江与多雄藏布河间的山谷地带、喜马拉雅山脉中段地带河谷区和喜马拉雅山东段北侧与雅鲁藏布江中游南岸相间地带是目前主要的适生区,而喜马拉雅山脉东部部分地区可能会成为藏波罗花的扩散分布区。展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 40839909, No. 41274077 and No. 41274078)
文摘Investigation of the deep geophysical structure of the Longmen Mountains tectonic belt and its relation to the Wenchuan Earthquake is important for the study of earthquakes.By using magnetotelluric sounding profiles of the Luqu-Zhongjiang and Anxian-Suining; seismic sounding profiles of the Sichuan Maowen-Chongqing Gongtan,the Qinghai Huashi Gorge-Sichuan Jianyang,and the Batang-Zizhong; and magnetogravimetric data of the Longmen Mountains region,the deep geophysical structure of the Songpan-Ganzi block,the western Sichuan foreland basin,and the Longmen Mountains tectonic belt and their relation was discussed.The eastward extrusion of the Qinghai-Tibet Plateau thrusts the Songpan-Ganzi block upon the Yangtze block,which obstructs the eastward movement of the Qinghai-Tibet Plateau.The Maoxian-Wenchuan,Beichuan-Yingxiu,and Anxian-Guanxian faults of the Longmen Mountains fault belt dip to northwest with different dip angles and gradually converge in the deeper parts.Geophysical structure suggests that an intracrustal low-velocity,low-resistivity,and high-conductivity layer is common between the middle and upper crust west of the Longmen Mountains tectonic belt but not in the upper Yangtze block.The Sichuan Basin has a thick low-resistance sedimentary layer on a stable high-resistance basement; moreover,there are secondary paleohighs and depression structures at the lower part of the western Sichuan foreland basin with characteristic of high magnetic anomalies,whereas the Songpan-Ganzi block has a high resisitivity cover of upper crust and continues to a low-resistance layer.Considering the Longmen Mountains tectonic belt as the boundary,there are Bouguer gravity anomalies of "one belt between two zones." Thus,we infer that there is a corresponding relation between the inferred crystalline basement of the Songpan block and the underlying basin basement of the Longmen Mountains fault belt.Furthermore,there may be an extensive ancient Yangtze block,which is west of the Ruoergai block.In addition,the crust-mantle ductile shear zone under the Longmen Mountains tectonic belt is the main fault,whereas the Beichuan-Yingxiu and Anxian-Guanxian faults at the surface are earthquake faults.The Wenchuan Ms 8.0 earthquake might be attributed to the collision of the Yangtze block and the Qinghai-Tibet Plateau.The eastward obduction of the eastern edge of the Qinghai-Tibet Plateau and eastward subduction of its deeper part under the influence of the collision of the Indian,Pacific,and Philippine Plates with the Eurasia Plate might have caused the Longmen Mountains tectonic belt to cut the Moho and extend to the middle and upper crust; thus,creating high stress concentration and rapid energy release zone.
基金National Key Technologies Research and Development Program of China(2014BAL07B02)Tibet Autonomous Region Science-technology Support Projects(201DKJGX01-38)
文摘藏波罗花Incarvillea younghusbandii是著名的藏药之一,极具开发和研究价值,但准确预测其潜在地理分布一直是目前尚未解决的关键问题。本文结合实地调查与现有研究数据,以气候和地表覆盖为环境变量,利用Maxent模型与GIS工具,对藏波罗花在西藏地区的潜在地理分布进行预测。研究结果表明:(1)Maxent模型对藏波罗花的潜在地理分布具有较高的预测精度,ROC曲线下面积(Area under the curve,AUC),训练AUC值可达0.994,测试AUC值可达0.996;(2)土壤类型、年降水量和生长繁育期降水量是影响藏波罗花生长分布的最重要环境因子;(3)藏波罗花在西藏有广泛的适生性,雅鲁藏布江与多雄藏布河间的山谷地带、喜马拉雅山脉中段地带河谷区和喜马拉雅山东段北侧与雅鲁藏布江中游南岸相间地带是目前主要的适生区,而喜马拉雅山脉东部部分地区可能会成为藏波罗花的扩散分布区。