Just after the occurrence of an M=5. 2 earthquake in Shimian, Sichuan, two three-component seismometerswere set up near the epicenter of, the earthquake. Field observations were made for the four-year period from1989 ...Just after the occurrence of an M=5. 2 earthquake in Shimian, Sichuan, two three-component seismometerswere set up near the epicenter of, the earthquake. Field observations were made for the four-year period from1989 to 1992. Analysis of the data recorded from either aftershocks following the M=5. 2 earthquake or fromsmall earthquakes scattered in this region indicates the presence of shear wave splitting. And shear wave splittingvaries with ti-cue. The mean direction of polarization of the faster shear waves is N18°W during the pened of aftershock activity, which is consistent with the strike of the faulting plane of the mainshock; but has turned toN46'W from 1990 to 1992, which is consistent with the regional maximum compressive stress. The time delaysbetween split shear waves measured on records from 1990 to 1992 are about half of that in 1989. The results ohtamed from observations at two temporary stations are similar. This indicates that the temporal changes may berelated to the occurrence of the M= 5.2 mainshock.展开更多
The high-resolution shallow seismic technique can be used for more accurately prospecting the position and property of faults and for the preliminary study of fault activity.The author obtains many high quality stack ...The high-resolution shallow seismic technique can be used for more accurately prospecting the position and property of faults and for the preliminary study of fault activity.The author obtains many high quality stack time sections through the prospecting methods of different seismic sources,different group intervals and different observation systems on the Xiadian fault.These sections clearly display the stratum structure and the structure characteristics from several meters to several hundred meters of the Xiadian fault.The resolutions of the different seismic sources,different group intervals and different observing systems are obtained.The prospecting methods and work parameters applicable for goal stratum of different depths and different accuracy requirements are proposed through the analysis of the stack time sections.This lays a good foundation for raising the prospecting resolution of the fault position and the latest active time of the fault.展开更多
地震P波、S波初至时间的拾取是地震波分析的一项基础性工作.本文提出了一种新的地震波初至时间自动拾取的方法:首先,把地震波的三分量时程曲线变换为一组空间向的能量变化率时程曲线;然后对能量变化率时程曲线进行STA/LTA(Short Time Av...地震P波、S波初至时间的拾取是地震波分析的一项基础性工作.本文提出了一种新的地震波初至时间自动拾取的方法:首先,把地震波的三分量时程曲线变换为一组空间向的能量变化率时程曲线;然后对能量变化率时程曲线进行STA/LTA(Short Time Average/Long Time Average,短时间的均值/长时间的均值)处理,拾取地震P波和S波的大致初至时间;最后提出采用一种二次方自回归模型对初至附近的能量变化率曲线进行二次方自回归处理,精确拾取出P波和S波的初至时间.本文采用了10组芦山地震的记录数据和150组汶川地震的记录数据对此方法的可靠性进行了检验.以人工拾取结果为参考,此方法具有很高的准确率和稳定性,同时,相比于常用的STA/LTA方法和AIC(Akaike Information Criterion,Akaike信息准则)方法,此方法在计算时间效率方面稍微逊色,但是对S波初至时间的拾取精度和可靠性更高.此方法丰富了地震P波、S波初至时间的自动拾取方法.展开更多
文摘Just after the occurrence of an M=5. 2 earthquake in Shimian, Sichuan, two three-component seismometerswere set up near the epicenter of, the earthquake. Field observations were made for the four-year period from1989 to 1992. Analysis of the data recorded from either aftershocks following the M=5. 2 earthquake or fromsmall earthquakes scattered in this region indicates the presence of shear wave splitting. And shear wave splittingvaries with ti-cue. The mean direction of polarization of the faster shear waves is N18°W during the pened of aftershock activity, which is consistent with the strike of the faulting plane of the mainshock; but has turned toN46'W from 1990 to 1992, which is consistent with the regional maximum compressive stress. The time delaysbetween split shear waves measured on records from 1990 to 1992 are about half of that in 1989. The results ohtamed from observations at two temporary stations are similar. This indicates that the temporal changes may berelated to the occurrence of the M= 5.2 mainshock.
基金supported by the project of "Experimental Exploration of Urban Active Faults" of the National Development and Reform Commission of China (20041138)
文摘The high-resolution shallow seismic technique can be used for more accurately prospecting the position and property of faults and for the preliminary study of fault activity.The author obtains many high quality stack time sections through the prospecting methods of different seismic sources,different group intervals and different observation systems on the Xiadian fault.These sections clearly display the stratum structure and the structure characteristics from several meters to several hundred meters of the Xiadian fault.The resolutions of the different seismic sources,different group intervals and different observing systems are obtained.The prospecting methods and work parameters applicable for goal stratum of different depths and different accuracy requirements are proposed through the analysis of the stack time sections.This lays a good foundation for raising the prospecting resolution of the fault position and the latest active time of the fault.
文摘地震P波、S波初至时间的拾取是地震波分析的一项基础性工作.本文提出了一种新的地震波初至时间自动拾取的方法:首先,把地震波的三分量时程曲线变换为一组空间向的能量变化率时程曲线;然后对能量变化率时程曲线进行STA/LTA(Short Time Average/Long Time Average,短时间的均值/长时间的均值)处理,拾取地震P波和S波的大致初至时间;最后提出采用一种二次方自回归模型对初至附近的能量变化率曲线进行二次方自回归处理,精确拾取出P波和S波的初至时间.本文采用了10组芦山地震的记录数据和150组汶川地震的记录数据对此方法的可靠性进行了检验.以人工拾取结果为参考,此方法具有很高的准确率和稳定性,同时,相比于常用的STA/LTA方法和AIC(Akaike Information Criterion,Akaike信息准则)方法,此方法在计算时间效率方面稍微逊色,但是对S波初至时间的拾取精度和可靠性更高.此方法丰富了地震P波、S波初至时间的自动拾取方法.
