Statistic analyses of sectional focal depth frequency relation for 1739 M S≥4.0 events in North China, 541 M S≥4.0 events in Xingtai seismic region and 999 M S≥4.0 events in Tangshan seismic region ...Statistic analyses of sectional focal depth frequency relation for 1739 M S≥4.0 events in North China, 541 M S≥4.0 events in Xingtai seismic region and 999 M S≥4.0 events in Tangshan seismic region have been carried out for the first step of the study. Then the sectional focal depth frequency diagrams (H N diagram) for each region were obtained. The study shows that: (1) The intraplate earthquakes in North China occur within the continental crust, and are mainly concentrated within a certain depth range of the middle and upper crust, making up a seismic source layer; (2) The seismic source layer consists of a main layer and an auxiliary layer adjacent to it. The tops and bottoms of the main and auxiliary layers correspond to the G and C, as well as to B and G geologic boundaries respectively; (3) The H N diagrams for Xingtai and Tangshan seismic regions are significantly different from each other, indicating the regionality and localization of the seismic source layers; (4) DSS and MTS observations show that the regionality and localization of the seismic source layer depend mainly on the environment of the deep structures of the region; (5) The seismic source layer is a substance of medium layer, which can be related to the brittle ductile transition zone within the crust. The seismic source layer is also a stress conducting layer. As the media above and below this layer are subjected to failure or flowage, then the stress will concentrate in the stress conducting layer, in which the earthquake occurs.展开更多
In this paper the differences and characteristics of the degree of seismic activities of various tectonic blocks and the different parts within the blocks in the eastern part of the Chinese mainland (to the east of 10...In this paper the differences and characteristics of the degree of seismic activities of various tectonic blocks and the different parts within the blocks in the eastern part of the Chinese mainland (to the east of 105°E) have been studied. Based on the results, the crust-mantle structural factors which caused these differences have further been studied from the inner and deep part of the plate. The ratio between the crustal and lithospheric thicknesses, i. e. the so-called crust-mantle structural ratio R, has been calculated. The result has shown that the magnitude of R has a close relation to the degree of seismic activity. The R-value implies the state of the movement of crust-mantle materials and the degree of interaction between the crust and mantle through convection and intrusion.展开更多
文摘Statistic analyses of sectional focal depth frequency relation for 1739 M S≥4.0 events in North China, 541 M S≥4.0 events in Xingtai seismic region and 999 M S≥4.0 events in Tangshan seismic region have been carried out for the first step of the study. Then the sectional focal depth frequency diagrams (H N diagram) for each region were obtained. The study shows that: (1) The intraplate earthquakes in North China occur within the continental crust, and are mainly concentrated within a certain depth range of the middle and upper crust, making up a seismic source layer; (2) The seismic source layer consists of a main layer and an auxiliary layer adjacent to it. The tops and bottoms of the main and auxiliary layers correspond to the G and C, as well as to B and G geologic boundaries respectively; (3) The H N diagrams for Xingtai and Tangshan seismic regions are significantly different from each other, indicating the regionality and localization of the seismic source layers; (4) DSS and MTS observations show that the regionality and localization of the seismic source layer depend mainly on the environment of the deep structures of the region; (5) The seismic source layer is a substance of medium layer, which can be related to the brittle ductile transition zone within the crust. The seismic source layer is also a stress conducting layer. As the media above and below this layer are subjected to failure or flowage, then the stress will concentrate in the stress conducting layer, in which the earthquake occurs.
文摘In this paper the differences and characteristics of the degree of seismic activities of various tectonic blocks and the different parts within the blocks in the eastern part of the Chinese mainland (to the east of 105°E) have been studied. Based on the results, the crust-mantle structural factors which caused these differences have further been studied from the inner and deep part of the plate. The ratio between the crustal and lithospheric thicknesses, i. e. the so-called crust-mantle structural ratio R, has been calculated. The result has shown that the magnitude of R has a close relation to the degree of seismic activity. The R-value implies the state of the movement of crust-mantle materials and the degree of interaction between the crust and mantle through convection and intrusion.
