2001年雅江6.0级地震序列震源机制解与应力场分析
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摘要
叙述了利用P波初动和短周期体波振幅联合测定震源机制解和利用震源机制解求取区域主应力张量的方法,采用成都遥测数字地震台网在2001年2月雅江Ms 5.0、Ms 6.0地震前后的3.0级以上的26个地震,共14个台站的垂直分向速度波形记录进行计算。使用主事件定位法,确定了这些地震较准确的震中位置,并在此后的计算中采用该数据。震源机制解结果表明:5.0和6.0级地震与另外3次地震为走滑型,呈北东向分布;而外围的其他21次地震全部是倾滑型。分析认为,雅江震区位于鲜水河断裂带南端西侧的以贡嘎山为中心的地壳隆起区内,地壳的抬升运动导致震源体的形成,两种破裂方式与之有关。前震与余震时段的最大主压应力σ1轴的方向大致相同,5.0和6.0级地震期间,σ1轴的方向偏转了约100°。
The method of joint determination of focal mechanism solution and stress field using P wave polarities and short-period body wave amplitudas are presented, using 26 earthquakes (M≥3) of 2001 Yajiang Ms5. 0 and Ms6. 0 earthquake sequence with 14 vertical component velocity waveform records which are from Chengdu telemetry seismic network. More accu-rate epicenter location data were obtained by use of the master event technique for the follow-ing computation. The results show that the focal mechanism solutions of 5 earthquakes (in-cluding Ms5. 0 and Ms6. 0) are strike slip type; and others are dip slip type. The further a-nalysis indicate that 2 rupture ways were resulted from the formation of earthquake focus which is caused by earth crust uplift motion, since Yajiang earthquake area is located at the south-west side of Xianshuihe fault zone and within the crust uplift region which Gonggas-han mountain is considered to be the center. In addition, the direction of major principal stress axis are almost the same before and after the main shock, but the direction rotated a-bout 100° during Ms5. 0 and Ms6. 0's occurrences.
The method of joint determination of focal mechanism solution and stress field using P wave polarities and short-period body wave amplitudas are presented, using 26 earthquakes (M≥3) of 2001 Yajiang Ms5. 0 and Ms6. 0 earthquake sequence with 14 vertical component velocity waveform records which are from Chengdu telemetry seismic network. More accu-rate epicenter location data were obtained by use of the master event technique for the follow-ing computation. The results show that the focal mechanism solutions of 5 earthquakes (in-cluding Ms5. 0 and Ms6. 0) are strike slip type; and others are dip slip type. The further a-nalysis indicate that 2 rupture ways were resulted from the formation of earthquake focus which is caused by earth crust uplift motion, since Yajiang earthquake area is located at the south-west side of Xianshuihe fault zone and within the crust uplift region which Gonggas-han mountain is considered to be the center. In addition, the direction of major principal stress axis are almost the same before and after the main shock, but the direction rotated a-bout 100° during Ms5. 0 and Ms6. 0's occurrences.
引文
陈天长,堀内茂木,郑斯华.2001． 利用P波初动和短周期P,S波振幅测定川滇地区地震震源机制解和应力场[J].地震学报,23(4) :436-440
范军等.利用遗传算法反演四川地区非弹性衰减系数、震源参数和场地响应[J].地震学报(待刊)
何玉林等.2002． 2001年2月23日四川省雅江-康定6． 0级地震宏观烈度考察及发震构造背景刍议[J].地震学报,24(1) :57-66
刘杰,郑斯华等.2004． 利用P波和S波的初动和振幅比计算中小地震的震源机制解[J].地震,24(1) :19-26
魏亚玲等.2001． 雅江地震的震源机制解与应力场[J].四川地震,4,17-20
Fitch T J. 1975． Compressional velocity in source regions of deep earthquakes; an application of the master event technique [J]. Earth Planet Sci Lett, 26,156-166
Gephart J W and Forsyth D W. 1984． An improved method for determining the regional stress tensor using earthquake focalmechanism data:application to the San Fernando earthquake sequence[J]. J G R, 89,9 305-9 320．
Nakamura A, Horiuchi S and Hasegawa A. 1999． Joint Focal mechanism Determination With Source-Region Station Cor-rections Using Short-Period Body-Wave Amplitude Data[J]. Bull Seism Soc Amer. 89, 373-383
Rutain T G, Khalturin V I, Martynov V G and Monlar P. 1978． Preliminary analysis of spectral content of P and S wavefrom local earthquakes in the Garm, Tadijikstan Region [J]. Bull Seism Soc Amer,68,949-971
范军等.利用遗传算法反演四川地区非弹性衰减系数、震源参数和场地响应[J].地震学报(待刊)
何玉林等.2002． 2001年2月23日四川省雅江-康定6． 0级地震宏观烈度考察及发震构造背景刍议[J].地震学报,24(1) :57-66
刘杰,郑斯华等.2004． 利用P波和S波的初动和振幅比计算中小地震的震源机制解[J].地震,24(1) :19-26
魏亚玲等.2001． 雅江地震的震源机制解与应力场[J].四川地震,4,17-20
Fitch T J. 1975． Compressional velocity in source regions of deep earthquakes; an application of the master event technique [J]. Earth Planet Sci Lett, 26,156-166
Gephart J W and Forsyth D W. 1984． An improved method for determining the regional stress tensor using earthquake focalmechanism data:application to the San Fernando earthquake sequence[J]. J G R, 89,9 305-9 320．
Nakamura A, Horiuchi S and Hasegawa A. 1999． Joint Focal mechanism Determination With Source-Region Station Cor-rections Using Short-Period Body-Wave Amplitude Data[J]. Bull Seism Soc Amer. 89, 373-383
Rutain T G, Khalturin V I, Martynov V G and Monlar P. 1978． Preliminary analysis of spectral content of P and S wavefrom local earthquakes in the Garm, Tadijikstan Region [J]. Bull Seism Soc Amer,68,949-971
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