The environment shear stress of Tangshan main earthquake and 38 great aftershocks have been calculated by the acceleration data of Tangshan earthquake sequence. The environment shear stress for 52 smaller aftershocks ...The environment shear stress of Tangshan main earthquake and 38 great aftershocks have been calculated by the acceleration data of Tangshan earthquake sequence. The environment shear stress for 52 smaller aftershocks from July of 1982 to July of 1984 have also been calculated by use of the digital data of the Sino-American cooperation recorded by the instrumental arrays in Tangshan. The results represent that the environment shear stress τ0 values have a weak dependence on the seismic moment, only the small and moderate earthquakes will be able to occur in the region with smaller τ0 value and the large earthquakes are only in the region with greater τ0 value. The peak acceleration, velocity and displacement will be larger for the earthquakes occurred in the region with greater τ0 value, Therefore, the measurement of environment shear stress τ0 value for the significant region will play an important role in earthquske prediction and engineering shock-proof. The environment shear stress values for the great aftershocks occurred in the two ends of the main fault are often higher than that for the main shock. This case may represent the stress concentration in the two ends of the fault. This phenomenon provides the references for the place where the great aftershock will occur.展开更多
The state of the stress fields in the source region is analysed systematically, on the basis of the focal mechanismsof 167 events with Ms≥4. 0 of Tangshan sequence and 163 moderate-small events of Lancang sequence re...The state of the stress fields in the source region is analysed systematically, on the basis of the focal mechanismsof 167 events with Ms≥4. 0 of Tangshan sequence and 163 moderate-small events of Lancang sequence respectively. The result indicates that the directions of the stress field in the source region are generally stable and thevariation is not obvious after the occurrence of strong shock. The dominant orientations of focal mechanisms ofthe aftershocks are consistent with that of the mainshock, there is still a small difference between some mechanisms of aftershocks and the mechanism of mainshock, and the difference decreases as time goes on. The numbers of solutions with dominant direction of Tangshan and Lancang sequences are similar to each other, it indicates that the controls of the strong earthquake sequences from the tectonic stress field are similar to each othertoo. Through the hierarchical clustering analysis of focal mechanism,it is found that the number of clusters ofTangshan sequence is larger than that of Lancang sequence,and their orientations are relatively disordered. Itmay be the cause that the tectonics in the Tangshan region are more complicated than those in the Lancang region.展开更多
文摘The environment shear stress of Tangshan main earthquake and 38 great aftershocks have been calculated by the acceleration data of Tangshan earthquake sequence. The environment shear stress for 52 smaller aftershocks from July of 1982 to July of 1984 have also been calculated by use of the digital data of the Sino-American cooperation recorded by the instrumental arrays in Tangshan. The results represent that the environment shear stress τ0 values have a weak dependence on the seismic moment, only the small and moderate earthquakes will be able to occur in the region with smaller τ0 value and the large earthquakes are only in the region with greater τ0 value. The peak acceleration, velocity and displacement will be larger for the earthquakes occurred in the region with greater τ0 value, Therefore, the measurement of environment shear stress τ0 value for the significant region will play an important role in earthquske prediction and engineering shock-proof. The environment shear stress values for the great aftershocks occurred in the two ends of the main fault are often higher than that for the main shock. This case may represent the stress concentration in the two ends of the fault. This phenomenon provides the references for the place where the great aftershock will occur.
文摘The state of the stress fields in the source region is analysed systematically, on the basis of the focal mechanismsof 167 events with Ms≥4. 0 of Tangshan sequence and 163 moderate-small events of Lancang sequence respectively. The result indicates that the directions of the stress field in the source region are generally stable and thevariation is not obvious after the occurrence of strong shock. The dominant orientations of focal mechanisms ofthe aftershocks are consistent with that of the mainshock, there is still a small difference between some mechanisms of aftershocks and the mechanism of mainshock, and the difference decreases as time goes on. The numbers of solutions with dominant direction of Tangshan and Lancang sequences are similar to each other, it indicates that the controls of the strong earthquake sequences from the tectonic stress field are similar to each othertoo. Through the hierarchical clustering analysis of focal mechanism,it is found that the number of clusters ofTangshan sequence is larger than that of Lancang sequence,and their orientations are relatively disordered. Itmay be the cause that the tectonics in the Tangshan region are more complicated than those in the Lancang region.
