Using digital wave data recorded by the Barkam station, source parameters for 93 earthquakes with ML2.5 - 5.0 in the Barkam area are determined by spectral analysis. PreHmiuary analysis of the source parameters show t...Using digital wave data recorded by the Barkam station, source parameters for 93 earthquakes with ML2.5 - 5.0 in the Barkam area are determined by spectral analysis. PreHmiuary analysis of the source parameters show that there is a high correlation between seismic moment Mo and local scale ML, which is lgtoMo = 0.92ML ＋ 10.24,correlation coefficient R is 0.86; Investigation of the relationship between stress drop and local scale ML indicates that the stress drop seems to be independent of ML.展开更多
Based on horizontal-component digital seismograms recorded on 6 stations of the Yunnan Regional Digital Network, we inversed the inelastic attenuation in the source region of the Shidian swarm using the Atkinson metho...Based on horizontal-component digital seismograms recorded on 6 stations of the Yunnan Regional Digital Network, we inversed the inelastic attenuation in the source region of the Shidian swarm using the Atkinson method and the site responses of the 6 stations 200kin around the Shidian epicenters using the Moya method. The observational seismic waveform data were corrected by removing the propagation, instrument and site effects before the source parameters of the Shidian swarm in 2001 were determined using genetic algorithms. The results are as follows： （ 1 ） There is a linear relation between seismic moment and local magnitude. The seismic moment is between 1×10^12 and 10^14 N·m. The rupture radius of the seismic focus varies from 157m to 973m. The seismic moment and the rupture radius maintain a linear correlation. （2） The corner frequency increases as the seismic moment decreases. Based on the expression between corner frequency and seismic moment using least squares fitting, we can obtain the estimated value of the corner frequency. The time-varying value of the calculated corner frequency minus the estimated corner frequency shows that there were continuous high and low anomalies before the strong aftershocks. （3） The seismic stress drop is in the range of 0.07-1.55MPa. The stress drop seems independent of the local magnitude. The variation of stress drops is high before the occurrence of the strong aftershocks. （4） The depth of aftershocks is mostly in a range from 5kin to 10km, which means that energy release of aftershocks is mainly concentrated in this range of depth.展开更多
The source parameters of the Yingjiang earthquake sequences in 2008 are obtained by applying spectral analysis and Brunes source model,based on the digital waveform data recorded by the Yunnan Digital Seismic Network....The source parameters of the Yingjiang earthquake sequences in 2008 are obtained by applying spectral analysis and Brunes source model,based on the digital waveform data recorded by the Yunnan Digital Seismic Network.The correlation coefficients are calculated using the low-frequency spectral amplitudes of 2 events recorded by a same station,then,events with similar focal mechanism are grouped using the clustering analysis method.Compared to the obtained focal mechanisms,it is found that there are good correlations with the azimuth of P axes in each clustering group,and the larger the correlation coefficient,the closer the azimuths of P axes.We divide the Yingjiang area into 3 regions to analyze the stress level and stress direction by combining the source parameters and the mean focal mechanism of each group.The results show:The change and transformation of the focal mechanism types at different stages can represent the temporal characteristics of the regional stress field.If the earthquake focal mechanism types are concentrated in a time period and switch to the direction of regional stress field,it may be a sign of strong earthquake.There is some relationship between the stress drop and the type of focal mechanism.Those earthquakes with stress fields revealed by focal mechanism types closer to the regional tectonic stress field will have higher stress drop,while those with the focal mechanism-revealed stress fields differing a lot from the regional tectonic stress field will generally have a lower stress drop.展开更多
基金This project was sponsored by the National Key Basic Research and Development Programof China (2004CB418404)
文摘Using digital wave data recorded by the Barkam station, source parameters for 93 earthquakes with ML2.5 - 5.0 in the Barkam area are determined by spectral analysis. PreHmiuary analysis of the source parameters show that there is a high correlation between seismic moment Mo and local scale ML, which is lgtoMo = 0.92ML ＋ 10.24,correlation coefficient R is 0.86; Investigation of the relationship between stress drop and local scale ML indicates that the stress drop seems to be independent of ML.
基金the State Science and Technology Programof Tackle Key Problemfor the tenth "Five-Year Plan" of China (2004BA601B01-04-03) and the Youth Fund of Earthquake Administration of Yunnan Province ,China
文摘Based on horizontal-component digital seismograms recorded on 6 stations of the Yunnan Regional Digital Network, we inversed the inelastic attenuation in the source region of the Shidian swarm using the Atkinson method and the site responses of the 6 stations 200kin around the Shidian epicenters using the Moya method. The observational seismic waveform data were corrected by removing the propagation, instrument and site effects before the source parameters of the Shidian swarm in 2001 were determined using genetic algorithms. The results are as follows： （ 1 ） There is a linear relation between seismic moment and local magnitude. The seismic moment is between 1×10^12 and 10^14 N·m. The rupture radius of the seismic focus varies from 157m to 973m. The seismic moment and the rupture radius maintain a linear correlation. （2） The corner frequency increases as the seismic moment decreases. Based on the expression between corner frequency and seismic moment using least squares fitting, we can obtain the estimated value of the corner frequency. The time-varying value of the calculated corner frequency minus the estimated corner frequency shows that there were continuous high and low anomalies before the strong aftershocks. （3） The seismic stress drop is in the range of 0.07-1.55MPa. The stress drop seems independent of the local magnitude. The variation of stress drops is high before the occurrence of the strong aftershocks. （4） The depth of aftershocks is mostly in a range from 5kin to 10km, which means that energy release of aftershocks is mainly concentrated in this range of depth.
基金funded under the National Science and Technology Support Program of the 12th "Five-year Plan",China(2012BAK19B02)
文摘The source parameters of the Yingjiang earthquake sequences in 2008 are obtained by applying spectral analysis and Brunes source model,based on the digital waveform data recorded by the Yunnan Digital Seismic Network.The correlation coefficients are calculated using the low-frequency spectral amplitudes of 2 events recorded by a same station,then,events with similar focal mechanism are grouped using the clustering analysis method.Compared to the obtained focal mechanisms,it is found that there are good correlations with the azimuth of P axes in each clustering group,and the larger the correlation coefficient,the closer the azimuths of P axes.We divide the Yingjiang area into 3 regions to analyze the stress level and stress direction by combining the source parameters and the mean focal mechanism of each group.The results show:The change and transformation of the focal mechanism types at different stages can represent the temporal characteristics of the regional stress field.If the earthquake focal mechanism types are concentrated in a time period and switch to the direction of regional stress field,it may be a sign of strong earthquake.There is some relationship between the stress drop and the type of focal mechanism.Those earthquakes with stress fields revealed by focal mechanism types closer to the regional tectonic stress field will have higher stress drop,while those with the focal mechanism-revealed stress fields differing a lot from the regional tectonic stress field will generally have a lower stress drop.
