武定6.5级地震序列的地震应力降研究
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摘要
以Brune提出的中小地震圆盘形破裂位错模式为理论基础 ,研究了地面运动峰值参数 (r d)和 (r v)对地震应力降Δσ的依赖性 ,并考虑地球介质Q值对峰值参数的影响 ,利用武定M6 5级地震序列的近场数字记录地震资料 ,由此导出了用峰值位移d和峰值速度v求地震应力降Δσ的关系式 :lg (r d/e-qr) =- 10 5 6+ 2 / 3lgM0 + 1/ 3lgΔσ ;lg (r v/e-qr) =- 2 5 6 6 + 1/ 3lgM0 + 2 / 3lgΔσ。用上述公式测定了武定地震序列的地震应力降Δσ ,结果给出地震序列的应力降Δσ绝大多数在 5 0～ 5 0MPa的范围内 ,是典型的高应力降序列。通过分析应力降的时空分布特征 ,发现应力参数与余震活动的频度及强度相关 ,也与地震构造背景相关。研究结果还表明用地面运动峰值参数估算地震应力降是一种新的实用性较强的方法。
Based on the source dislocation model for medium and small earthquakes suggested by Brune,the dependence of ground motion pead parameters(r,v)on the seismic stress drop is studied,and considering influence of the Q value on the peak parameters and usin nearfield digital seismic data of the Wuding Ms 6 5 earthquake sequence,the relations calculating the seismic stress drop Δσ from the peak displacement d and the peak velocity v,lg(r,d/e -qr )=-10 56+2/3lg Mo+1/3lg Mo+1/3lgΔσ and lg(r,v/e -qr )=-2 566+1/3lg Mo+2/3lgΔσ are derived.By using above,the seismic stress drops for the Wuding earthquake sequence are determined and most of them fell inside the limits of 5 0～50 Mpa and the Wuding earthquake sequence is typical high stress sequence.It is found from analyzing time-space distribution characteristics that the stress parameters are correlated not only with the frequency and intensity of aftershock activity,but also with seismotectonic background.The results of this study also show that estimation of seismic stress drop from the peak parameters of ground motion will become a new practical method.
Based on the source dislocation model for medium and small earthquakes suggested by Brune,the dependence of ground motion pead parameters(r,v)on the seismic stress drop is studied,and considering influence of the Q value on the peak parameters and usin nearfield digital seismic data of the Wuding Ms 6 5 earthquake sequence,the relations calculating the seismic stress drop Δσ from the peak displacement d and the peak velocity v,lg(r,d/e -qr )=-10 56+2/3lg Mo+1/3lg Mo+1/3lgΔσ and lg(r,v/e -qr )=-2 566+1/3lg Mo+2/3lgΔσ are derived.By using above,the seismic stress drops for the Wuding earthquake sequence are determined and most of them fell inside the limits of 5 0～50 Mpa and the Wuding earthquake sequence is typical high stress sequence.It is found from analyzing time-space distribution characteristics that the stress parameters are correlated not only with the frequency and intensity of aftershock activity,but also with seismotectonic background.The results of this study also show that estimation of seismic stress drop from the peak parameters of ground motion will become a new practical method.
引文
〔1〕秦嘉政、刘祖荫、蒋乐群 .滇西实验场区微震序列的环境应力值特征 .地震学报 ,1995 ,17(4) :45 9～ 46 8.
〔2〕陈培善 ,DudaS .J ..峰值速度和加速度对环境应力的依赖性 .地球物理学报 ,1993,36 (2 ) :185～ 194.
〔3〕秦嘉政 ,刘祖荫 ,钱晓东 ,谢庆茵 .由峰值速度估算应力降 .地震学报 ,1997,19(5 ) :471～ 479.
〔4〕秦嘉政 ,谢庆茵 ,钱晓东 ,张俊伟 .武定地震序列的震源参数与频率特征 .地震地磁观测与研究 ,1999,2 0 (3) :13～ 17.
〔5〕Brune ,J.N ..Tectonicstressandspectraofseismicshearwavefromearthquake .J .Geophys.Res .,1970 ,75 (4) :4997～ 5 0 0 9.
〔6〕McGarr ,A ..Scalingofgroundmotionparameters ,stateofstressandfocaldepth .J .Geophys .Res .,1984,89(5 ) :6 96 9～ 6 979.
〔2〕陈培善 ,DudaS .J ..峰值速度和加速度对环境应力的依赖性 .地球物理学报 ,1993,36 (2 ) :185～ 194.
〔3〕秦嘉政 ,刘祖荫 ,钱晓东 ,谢庆茵 .由峰值速度估算应力降 .地震学报 ,1997,19(5 ) :471～ 479.
〔4〕秦嘉政 ,谢庆茵 ,钱晓东 ,张俊伟 .武定地震序列的震源参数与频率特征 .地震地磁观测与研究 ,1999,2 0 (3) :13～ 17.
〔5〕Brune ,J.N ..Tectonicstressandspectraofseismicshearwavefromearthquake .J .Geophys.Res .,1970 ,75 (4) :4997～ 5 0 0 9.
〔6〕McGarr ,A ..Scalingofgroundmotionparameters ,stateofstressandfocaldepth .J .Geophys .Res .,1984,89(5 ) :6 96 9～ 6 979.
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