In accordance with the studies concerning the tectonics of Nei Monggolmade by Huang Jiqing and others, two tectonic units occur in this area:Sino-Korean Platform to the south and Nei Monggol-Greater Khingan Mtsfold sy...In accordance with the studies concerning the tectonics of Nei Monggolmade by Huang Jiqing and others, two tectonic units occur in this area:Sino-Korean Platform to the south and Nei Monggol-Greater Khingan Mtsfold system to the north. The dividing line between the two units lies fromBaiyun’ebo on the west to Chifeng on the east. Geophysical studies demonst-rate that there are two gravity gradient zones trending ENE in the northernmargin of the North China Platform. The northern zone is a linear anomalyzone of--50 to--45 mGal extending from Baiyun’ebo in the west to theeast of Chifeng. The southern zone, 60--70km wide, lies from Guyang throughJining to Longhua in the east and its amplitude of gravity gradient amountsto 60 mGal. Field geological survey indicates that there are two main faultedzones. Our recent investigations suggests that there are two Proterozoic riftsof E-W trend in the northern margin of the North China Platform.展开更多
It can be inferred from the geophysical data, linear structures, tectonic evolu-tion history and metallogeny that the S-N tectonic Belt stretches further south in a different di-rection and manner after intercepted by...It can be inferred from the geophysical data, linear structures, tectonic evolu-tion history and metallogeny that the S-N tectonic Belt stretches further south in a different di-rection and manner after intercepted by the Red River Fault, The stretching segment is the im-portant tectonic boundary in Indo-Asia and assiminlates the S-N tectonic belt with some differ-ences.展开更多
In this paper,the focal mechanisms of the fore-main-after shocks of the 1989 Datong-Yanggao earthquake are determined by fitting Pnl and SH waveforms,and the earthquake processes and seismotectonics are inferred.The r...In this paper,the focal mechanisms of the fore-main-after shocks of the 1989 Datong-Yanggao earthquake are determined by fitting Pnl and SH waveforms,and the earthquake processes and seismotectonics are inferred.The results show that the fore-main-after shocks occurred on a composite fault plane,The fault motion at the shallow part is right-lateral strike-slip with mechanisms:strike 201,dip 75,rake 191; at the deeper part,the fault movement is strike 201,dip 58,rake 222.The epicentral area is subject to a ENE-WSW horizontal compression and a NNW-SSE extension which is consistent with the tectonic stress orientation of North China.The P-axis at greater depth has an azimuth of 54.5 and a plunge of 51.The relatively large P-axis plunge in depth corresponds with the great depressive deformation in this area.In addition,the similarities and differences between the Datong-Yanggao earthquakes and general graben-associated earthquakes are discusses.展开更多
The 1:6,000,000 Epicenter Distribution Map of China compiled by the Center for Analysis and Prediction,SSB,has given more than 100,000 epicenters of large and small earthquakes.The images composed of these dots contai...The 1:6,000,000 Epicenter Distribution Map of China compiled by the Center for Analysis and Prediction,SSB,has given more than 100,000 epicenters of large and small earthquakes.The images composed of these dots contain plenty of information concerning the structures in the middle-upper crust.Using the so-called visual seismic line method,a tectonic interpretation of the epicenter distribution map of shallow focus earthquakes in China mainland is given in this paper,and the seismotectonic patterns and dynamic characteristics of the Tianshan,AIxa-Qilianshan and Qinghai-Xizang(Tibet)seismic belts,the S-N central axis belt as well as Northeast China,North China,the middle and lower reaches of the Yangtze River and the southeast coastal areas are analyzed and interpreted.展开更多
文摘In accordance with the studies concerning the tectonics of Nei Monggolmade by Huang Jiqing and others, two tectonic units occur in this area:Sino-Korean Platform to the south and Nei Monggol-Greater Khingan Mtsfold system to the north. The dividing line between the two units lies fromBaiyun’ebo on the west to Chifeng on the east. Geophysical studies demonst-rate that there are two gravity gradient zones trending ENE in the northernmargin of the North China Platform. The northern zone is a linear anomalyzone of--50 to--45 mGal extending from Baiyun’ebo in the west to theeast of Chifeng. The southern zone, 60--70km wide, lies from Guyang throughJining to Longhua in the east and its amplitude of gravity gradient amountsto 60 mGal. Field geological survey indicates that there are two main faultedzones. Our recent investigations suggests that there are two Proterozoic riftsof E-W trend in the northern margin of the North China Platform.
基金Supported the Key project of Academia Sinica Funds "Establishment and application of hisoric-casationist tectonics.
文摘It can be inferred from the geophysical data, linear structures, tectonic evolu-tion history and metallogeny that the S-N tectonic Belt stretches further south in a different di-rection and manner after intercepted by the Red River Fault, The stretching segment is the im-portant tectonic boundary in Indo-Asia and assiminlates the S-N tectonic belt with some differ-ences.
文摘In this paper,the focal mechanisms of the fore-main-after shocks of the 1989 Datong-Yanggao earthquake are determined by fitting Pnl and SH waveforms,and the earthquake processes and seismotectonics are inferred.The results show that the fore-main-after shocks occurred on a composite fault plane,The fault motion at the shallow part is right-lateral strike-slip with mechanisms:strike 201,dip 75,rake 191; at the deeper part,the fault movement is strike 201,dip 58,rake 222.The epicentral area is subject to a ENE-WSW horizontal compression and a NNW-SSE extension which is consistent with the tectonic stress orientation of North China.The P-axis at greater depth has an azimuth of 54.5 and a plunge of 51.The relatively large P-axis plunge in depth corresponds with the great depressive deformation in this area.In addition,the similarities and differences between the Datong-Yanggao earthquakes and general graben-associated earthquakes are discusses.
文摘The 1:6,000,000 Epicenter Distribution Map of China compiled by the Center for Analysis and Prediction,SSB,has given more than 100,000 epicenters of large and small earthquakes.The images composed of these dots contain plenty of information concerning the structures in the middle-upper crust.Using the so-called visual seismic line method,a tectonic interpretation of the epicenter distribution map of shallow focus earthquakes in China mainland is given in this paper,and the seismotectonic patterns and dynamic characteristics of the Tianshan,AIxa-Qilianshan and Qinghai-Xizang(Tibet)seismic belts,the S-N central axis belt as well as Northeast China,North China,the middle and lower reaches of the Yangtze River and the southeast coastal areas are analyzed and interpreted.
