This paper deals with the response features of AR(apparent ratio of seismic wave velocities to the changes of TR(true ratio of wave velocities)in the horizontal layered model by mathematical modeling.The results show ...This paper deals with the response features of AR(apparent ratio of seismic wave velocities to the changes of TR(true ratio of wave velocities)in the horizontal layered model by mathematical modeling.The results show that:(1)the response features of AR are associated with the parameters of the structure and its dynamic changes,and the relative position between the hypocenters and the monitoring networks,showing complicated patterns strongly related to the concrete paths of propagation of seismic waves from the source to the receiver in the observatories of the network;(2)the depth of the seismic source would have important influence on the response features of AR,especially the capacity to carry the anomalous information in the condition of the earth media,being in the anomalous state would be greater for those earthquakes which occur inside the anomalous layers than those underneath the anomalous layers;(3)the response features of AR are clearly related to the changes of TR(true ratio of wave velocities)instead of changes of wave velocities themselves,i.e.the response could be small as the changes in TR is small even in the case of large changes in the wave velocities.It is suggested that more attention must be paid to all these features in combination with detailed investigation of the velocity structure of the earth media in the study region and best fitting of precise hypocenter locations when one wants to obtain the reliable precursors from the changes in AR.展开更多
At 19:33 p.m on September 27, 2003, an earthquake with M7.9 occurred in the Russia-Mongolia-China boundary Region. It was strongly felt in the Altay region of Xinjiang. The losses caused by the earthquake was 76 milli...At 19:33 p.m on September 27, 2003, an earthquake with M7.9 occurred in the Russia-Mongolia-China boundary Region. It was strongly felt in the Altay region of Xinjiang. The losses caused by the earthquake was 76 million yuan (RMB). Some information about the earthquake was outlined, including basic parameters, focal mechanism, evaluation of earthquake disaster losses and so on. The satellite remote sensing information worked initial analysis for deformation of ground and failure phenomenon.展开更多
The amplitudes of the Earth＇s free oscillations have a close relationship to earthquake focal mechanisms. Focal mechanisms of large earthquakes can be well analyzed and constrained with observations of long period fr...The amplitudes of the Earth＇s free oscillations have a close relationship to earthquake focal mechanisms. Focal mechanisms of large earthquakes can be well analyzed and constrained with observations of long period free oscillations. Although the 2013 Lushan earthquake was only moderately sized, observable spherical normal modes were excited and clearly observed by a su- perconductive gravimeter and a broadband seismometer. We compare observed free oscillations with synthetic normal modes corresponding to four different focal mechanisms for the Lushan earthquake. The results show that source parameters can be analyzed and constrained by spherical normal modes in a 2.3-5 mHz frequency band. The scalar seismic moment M~ has a major influence on the amplitudes of free oscillations; additionally, the strike, dip, rake and depth of the hypocenter have mi- nor influences. We found that the synthetic modes corresponding to the focal mechanism determined by the Global Centroid Moment Tensor show agreement to the observed modes, suggesting that earthquake magnitudes predicted in this way can readily reflect the total energy released by the earthquake. The scalar seismic moment obtained by far-field body wave inver- sion is significantly underestimated. Focal mechanism solutions can be improved by joint inversion of far- and near-field data.展开更多
文摘This paper deals with the response features of AR(apparent ratio of seismic wave velocities to the changes of TR(true ratio of wave velocities)in the horizontal layered model by mathematical modeling.The results show that:(1)the response features of AR are associated with the parameters of the structure and its dynamic changes,and the relative position between the hypocenters and the monitoring networks,showing complicated patterns strongly related to the concrete paths of propagation of seismic waves from the source to the receiver in the observatories of the network;(2)the depth of the seismic source would have important influence on the response features of AR,especially the capacity to carry the anomalous information in the condition of the earth media,being in the anomalous state would be greater for those earthquakes which occur inside the anomalous layers than those underneath the anomalous layers;(3)the response features of AR are clearly related to the changes of TR(true ratio of wave velocities)instead of changes of wave velocities themselves,i.e.the response could be small as the changes in TR is small even in the case of large changes in the wave velocities.It is suggested that more attention must be paid to all these features in combination with detailed investigation of the velocity structure of the earth media in the study region and best fitting of precise hypocenter locations when one wants to obtain the reliable precursors from the changes in AR.
文摘At 19:33 p.m on September 27, 2003, an earthquake with M7.9 occurred in the Russia-Mongolia-China boundary Region. It was strongly felt in the Altay region of Xinjiang. The losses caused by the earthquake was 76 million yuan (RMB). Some information about the earthquake was outlined, including basic parameters, focal mechanism, evaluation of earthquake disaster losses and so on. The satellite remote sensing information worked initial analysis for deformation of ground and failure phenomenon.
基金supported by the National Basic Research Program of China (Grant No. 2014CB845902)National Natural Science Foundation of China (Grant Nos. 41174022, 4127408 and 41021003)
文摘The amplitudes of the Earth＇s free oscillations have a close relationship to earthquake focal mechanisms. Focal mechanisms of large earthquakes can be well analyzed and constrained with observations of long period free oscillations. Although the 2013 Lushan earthquake was only moderately sized, observable spherical normal modes were excited and clearly observed by a su- perconductive gravimeter and a broadband seismometer. We compare observed free oscillations with synthetic normal modes corresponding to four different focal mechanisms for the Lushan earthquake. The results show that source parameters can be analyzed and constrained by spherical normal modes in a 2.3-5 mHz frequency band. The scalar seismic moment M~ has a major influence on the amplitudes of free oscillations; additionally, the strike, dip, rake and depth of the hypocenter have mi- nor influences. We found that the synthetic modes corresponding to the focal mechanism determined by the Global Centroid Moment Tensor show agreement to the observed modes, suggesting that earthquake magnitudes predicted in this way can readily reflect the total energy released by the earthquake. The scalar seismic moment obtained by far-field body wave inver- sion is significantly underestimated. Focal mechanism solutions can be improved by joint inversion of far- and near-field data.
