龙门山断层破裂的频率非平稳特性
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摘要
为研究地震过程中的频率非平稳特性,对近年来龙门山断层发生的两次大地震:汶川大地震和芦山大地震的近断层地震记录进行频谱分析。结果表明:相对于芦山地震有较大走向滑动分量的汶川地震,大多数位于汶川地震断层滑动前方的台站接收到更高的频率成分,位于断层滑动后方的台站接收到的地震波频率较低;尽管芦山地震断层相对汶川地震有较小的走向滑动分量,但仍然可以得出与汶川地震相同的结论,不同的是虽然芦山地震沿断层面向上方向分量大,但是其同一台站东西、南北、竖直三方向分量记录幅值相当。把芦山地震三分量记录变换到走向和沿断层面向上方向,证实了沿断层面向上方向高频成分更丰富。在断层滑动前方接收到的地震波频率较高,在断层滑动后方接收到的频率较低,这正是多普勒效应影响的结果。由于多普勒效应的客观存在,其对频率非平稳特性的影响与震源、传播路径和场地效应一样具有普遍性;所以,工程场地接收到的地震波的频率不仅取决于震源、传播路径、场地效应,还取决于断层滑动速度(多普勒效应)。
In order to study the frequency non-stationary characteristics in seismic process,the frequency spectra were analyzed for the two major earthquakes occurred in Longmenshan fault in recent years.The near fault seismic records of Wenchuan and Lushan earthquakes show that compared to Lushan earthquake,Wenchuan earthquake has large strike-slip components.Most stations located in front of fault slip of Wenchuan earthquake received higher frequency components,while stations located behind fault slip received lower frequency components.Although Lushan seismic fault has the smaller strike-slip component than that of Wenchuan earthquake,the conclusions that are the same as Wenchuan earthquake can still be drawn.The difference is that although the dip-slip component of Lushan earthquake is large than that of Wenchuan earthquake,the amplitude of the three-direction components recorded in the same station match each other in magnitude.We transformed the threecomponent records of Lushan earthquake into the directon of strike-slip and upward direction along the fault plane,it is proved that the high-frequency components in the upward direction along the fault plane are more abundant.Higher seismic wave frequency is received in front of the fault slip and lower frequency is received behind the fault slip,which is the result of Doppler effect.Due to the objective existence of Doppler effect,its influence on frequency non-stationary characteristics is as universal as source,propagation path and site effect.Therefore,the seismic wave frequency received in engineering site depends not only on the source,propagation path,site effect,but also on the fault sliding velocity(Doppler effect).
In order to study the frequency non-stationary characteristics in seismic process,the frequency spectra were analyzed for the two major earthquakes occurred in Longmenshan fault in recent years.The near fault seismic records of Wenchuan and Lushan earthquakes show that compared to Lushan earthquake,Wenchuan earthquake has large strike-slip components.Most stations located in front of fault slip of Wenchuan earthquake received higher frequency components,while stations located behind fault slip received lower frequency components.Although Lushan seismic fault has the smaller strike-slip component than that of Wenchuan earthquake,the conclusions that are the same as Wenchuan earthquake can still be drawn.The difference is that although the dip-slip component of Lushan earthquake is large than that of Wenchuan earthquake,the amplitude of the three-direction components recorded in the same station match each other in magnitude.We transformed the threecomponent records of Lushan earthquake into the directon of strike-slip and upward direction along the fault plane,it is proved that the high-frequency components in the upward direction along the fault plane are more abundant.Higher seismic wave frequency is received in front of the fault slip and lower frequency is received behind the fault slip,which is the result of Doppler effect.Due to the objective existence of Doppler effect,its influence on frequency non-stationary characteristics is as universal as source,propagation path and site effect.Therefore,the seismic wave frequency received in engineering site depends not only on the source,propagation path,site effect,but also on the fault sliding velocity(Doppler effect).
引文
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[14]王卫民,郝金来,姚振兴.2013年4月20日四川芦山地震破裂过程反演初步结果[J].地球物理学报,2013,56(4):1412-1417.Wang Weimin,Hao Jinlai,Yao Zhenxing.Preliminary Result for Rupture Process of April 20,2013,Lushan Earthquake,Sichuan[J].Chinese Journal of Geophysics,2013,56(4):1412-1417.
[15]Boore D M.Simulation of Ground Motion Using the Stochastic Method[J].Pure and Applied Geophysics,2003,160(3/4):635-676.
[16]Boore D M,Thompson E M.Revisions to Some Parameters Used in Stochastic-Method Simulations of Ground Motion[J].Bulletin of Seismological Society of America,2015,105:1029-1041.
[17]Boore D M.Determining Generic Velocity and Density Models for Crustal Amplification Calculations,with an Update of the Boore and Joyner(1997)Generic Site Amplification for珚VS(Z)=760m/s[J].Bulletin of Seismological Society of America,2016,106:316-320.
[18]孙建国,李懿龙,孙章庆,等.基于模型参数化的地震波走时与射线路径计算[J].吉林大学学报(地球科学版),2018,48(2):343-349.Sun Jianguo,Li Yilong,Sun Zhangqing,et al.Computation of Seismic Traveltimes and Raypath Based on Model Parameterization[J].Journal of Jilin University(Earth Science Edition),2018,48(2):343-349.
[2]Midorikawa S.Rupture History of the 1979Imperial Valley Earthquake Eatimated from EL Centro StrongMotion Accelerograms[C]//Proceedings of Ninth World Conference on Earthquake Engineering:VolⅡ.Tokyo-kyoto:Conference Committee,1988:277-282.
[3]Mavroeidis G P,Papageorgiou A S.Sear-Source Strong Ground Motion:Characteristics and Design Issues[C]//Proceedings of the Seventh U S National Conference on Earthquake Engineering(7NCEE).Boston:Massachusetts,2002:21-25.
[4]Wang G Q,Zhou X Y,Zhang P Z,et al.Characteristics of Amplitude and Duration for Near Fault Strong Ground Motion from 1999 Chi-Chi,Taiwan Earthquake[J].Soil Dynamics and Earthquake Engineering,2002,22:73-96.
[5]谢俊举,温增平,高孟谭,等.2008年汶川近断层地震动的非平稳特征[J].地球物理学报,2011,54(3):728-736.Xie Junju,Wen Zengping,Gao Mengtan,et al.NonStationary Characteristics of Near-Fault Strong Motions During the 2008 Wenchuan Earthquake[J].Chinese Journal of Geophysics,2011,54(3):728-736.
[6]任叶飞,温瑞智,周宝峰,等.2103年4月20日四川芦山地震强地面运动三要素特征分析[J].地球物理学报,2014,57(6):1836-1846.Ren Yefei,Wen Ruizhi,Zhou Baofeng,et al.The Characteristics of Strong Ground Motion of Lushan Earthquake on April 20,2013[J].Chinese Journal of Geophysics,2014,57(6):1836-1846.
[7]Conte J P,Peng B F.Fully Non-Stationary Analytical Earthquake Ground-Motion Model[J].Journal of Engineering Mechanics,1997,123(1):30-35.
[8]梁爱虎,杜修力,陈厚群.基于非平稳随机地震动场的拱坝随机地震反应分析方法[J].水利学报,1999(6):21-25.Liang Aihu,Du Xiuli,Chen Houqun.Random Seismic Response Analysis of Arch Dams Based on NonStationary Random Earthquake Motion Field[J].Journal of Hydraulic Engineering,1999(6):21-25.
[9]曹晖,林学鹏.地震动非平稳特性对结构非线性响应影响的分析[J].工程力学,2006,23(12):30-35.Cao Hui,Lin Xuepeng.The Effect of Non-Stationary Characteristic of Earthquake Ground Motion on the Structural Nonlinear Response[J].Engineering Mechanics,2006,23(12):30-35.
[10]朱守彪,袁杰.2008年汶川大地震单侧破裂过程的动力学机制研究[J].地球物理学报,2016,59(11):4063-4074.Zhu Shoubiao,Yuan Jie.Mechanisms for the Fault Rupture of the 2008 Wenchuan Earthquake(Ms=8.0)with Predominantly Unilateral Propagation[J].Chinese Journal of Geophysics,2016,59(11):4063-4074.
[11]张勇,冯万鹏,许力生,等.2008年汶川大地震的时空破裂过程[J].中国科学:D辑:地球科学,2008,38(10):1186-1198.Zhang Yong,Feng Wanpeng,Xu Lisheng,et al.The Time and Space Rupture Process of the Wenchuan Earthquake in 2008[J].China Science:Science D:Earth Science,2008,38(10):1186-1198.
[12]刘杰,易桂喜,张致伟,等.2013年4月20日四川芦山M7.0级地震介绍[J].地球物理学报,2013,56(4):1404-1407.Liu Jie,Yi Guixi,Zhang Zhiwei,et al.Instroduction to Luahan,Sichuan M7.0 Earthquake on 20 April2013[J].Chinese Journal of Geophysics,2013,56(4):1404-1407.
[13]张广伟,雷建设.四川芦山7.0级强震及其余震序列重定位[J].地球物理学报,2013,56(5):1764-1771.Zhang Guangwei,Lei Jianshe.Relocations of Lushan,Sichuan Strong Earthquake(Ms7.0)and Its Aftershock[J].Chinese Journal of Geophysics,2013,56(5):1764-1771.
[14]王卫民,郝金来,姚振兴.2013年4月20日四川芦山地震破裂过程反演初步结果[J].地球物理学报,2013,56(4):1412-1417.Wang Weimin,Hao Jinlai,Yao Zhenxing.Preliminary Result for Rupture Process of April 20,2013,Lushan Earthquake,Sichuan[J].Chinese Journal of Geophysics,2013,56(4):1412-1417.
[15]Boore D M.Simulation of Ground Motion Using the Stochastic Method[J].Pure and Applied Geophysics,2003,160(3/4):635-676.
[16]Boore D M,Thompson E M.Revisions to Some Parameters Used in Stochastic-Method Simulations of Ground Motion[J].Bulletin of Seismological Society of America,2015,105:1029-1041.
[17]Boore D M.Determining Generic Velocity and Density Models for Crustal Amplification Calculations,with an Update of the Boore and Joyner(1997)Generic Site Amplification for珚VS(Z)=760m/s[J].Bulletin of Seismological Society of America,2016,106:316-320.
[18]孙建国,李懿龙,孙章庆,等.基于模型参数化的地震波走时与射线路径计算[J].吉林大学学报(地球科学版),2018,48(2):343-349.Sun Jianguo,Li Yilong,Sun Zhangqing,et al.Computation of Seismic Traveltimes and Raypath Based on Model Parameterization[J].Journal of Jilin University(Earth Science Edition),2018,48(2):343-349.