地震视应力在云南地震序列中的前兆特征
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摘要
在假设震源位移谱符合ω平方模型的基础上,得到了利用震源位移谱低频水平与拐角频率来计算中小地震视应力值的数学表达式.采用数字化速度波形记录,通过校正仪器响应、介质衰减与吸收效应、台站场地响应等影响因素后,计算得到了云南地区4个地震序列共823次中小地震的视应力值.结果表明,地震视应力在云南地区的这4个地震序列中有很好的前兆特征表现,即:地震序列中只要发生了视应力值超过1MPa的中小地震,其后就一定会有中强震发生;如果序列中中强地震发生后再没有发生视应力值超过1MPa的中小地震,则该序列就不会有强余震发生.同时研究表明,4个地震序列所在地区的平均视应力值为0.8MPa,地震视应力值与地震震级没有显著相关关系.
On the basis of the assumption that ω2 model accords with source displacement spectra, we have obtained the mathematical expressions for calculating apparent stresses of moderate-small shocks from low-frequency flat level and corner frequency. By using digital seismic records, apparent stress values are calculated for 823 moderate-small shocks of 4 earthquake series in Yunnan area following corrections for instrument response, propagation influence and site effect. The results show that for the 4 earthquake series in Yunnan area, apparent stress hints precursory information, which means that if a moderate-small shock occurs with apparent stress larger than 1 MPa in an earthquake series, a moderate-strong earthquake will occur afterwards; and if there is no moderate-small shock with apparent stress larger than 1 MPa after a moderate-strong event in an earthquake series, strong aftershock will not occur. The research also indicates that the average apparent stress value is 0.8 MPa in Yunnan area, therefore, apparent stress is not obviously related to seismic magnitude.
On the basis of the assumption that ω2 model accords with source displacement spectra, we have obtained the mathematical expressions for calculating apparent stresses of moderate-small shocks from low-frequency flat level and corner frequency. By using digital seismic records, apparent stress values are calculated for 823 moderate-small shocks of 4 earthquake series in Yunnan area following corrections for instrument response, propagation influence and site effect. The results show that for the 4 earthquake series in Yunnan area, apparent stress hints precursory information, which means that if a moderate-small shock occurs with apparent stress larger than 1 MPa in an earthquake series, a moderate-strong earthquake will occur afterwards; and if there is no moderate-small shock with apparent stress larger than 1 MPa after a moderate-strong event in an earthquake series, strong aftershock will not occur. The research also indicates that the average apparent stress value is 0.8 MPa in Yunnan area, therefore, apparent stress is not obviously related to seismic magnitude.
引文
黄福明,易志刚.2000.地震视应变场的演化与强震发生地区的关系[J].地震学报,22(6):577~587
刘红桂,缪发军,吴晶.2004.场地响应、震源参数与介质衰减的同时反演[J].地震,24(4):27~36
刘杰,郑斯华,黄玉龙.2003.利用遗传算法反演非弹性衰减系数、震源参数和场地响应[J].地震学报,25(2):211~218
吴忠良,黄静,林碧苍.2002.中国西部地震视应力的空间分布[J].地震学报,24(3):293~301
Andrews DJ.1986.Objective determination of source parameters and si milarity of earthquakes of different size[J].Geo-physical Monographs,37(6):259~267
Brune J N.1970.Tectonic stress and the spectra of seismic shear waves fromearthquake[J].J Geophys Res,75:4997~5009
Choy G L,Boatwright J L.1995.Global patterns of radiated seismic energy and apparent stress[J].J Geophys Res,100:18205~18228
Eric P Chael.1987.Spectral scaling of earthquakesinthe Miramichi region of New Brunswick[J].Bull SeismSoc Amer,77(2):347~365
McGarr A.1999.On relating apparent stress to the stress causing earthquake fault slip[J].J Geophys Res,104:3003~3011
Newman A V,Okal E A.1998.Teleseismic esti mates of radiated seismic energy:TheE/M0discri minant for Tsunamiearthquakes[J].J Geophys Res,103:26885~26898
Pulido N,Irikura K.2000.Esti mation of dynamic rupture parameters from the radiated seismic energy and apparentstress[J].Geophys Res Lett,27:3945~3948
Wyss M,Brune J N.1968.Seismic moment,stress,and source di mensions for earthquakesin the California-Nevada Re-gion[J].J Geophys Res,73(14):4681~4694
Wyss M.1970a.Stress esti mates for South American shallowand deep earthquake[J].J Geophys Res,75(8):1529~1544
Wyss M.1970b.Apparent stresses esti mates of earthquakes on ridges compared to apparent stresses of earthquakes inTrenches[J].Geophys J R astr Soc,19:479~484
刘红桂,缪发军,吴晶.2004.场地响应、震源参数与介质衰减的同时反演[J].地震,24(4):27~36
刘杰,郑斯华,黄玉龙.2003.利用遗传算法反演非弹性衰减系数、震源参数和场地响应[J].地震学报,25(2):211~218
吴忠良,黄静,林碧苍.2002.中国西部地震视应力的空间分布[J].地震学报,24(3):293~301
Andrews DJ.1986.Objective determination of source parameters and si milarity of earthquakes of different size[J].Geo-physical Monographs,37(6):259~267
Brune J N.1970.Tectonic stress and the spectra of seismic shear waves fromearthquake[J].J Geophys Res,75:4997~5009
Choy G L,Boatwright J L.1995.Global patterns of radiated seismic energy and apparent stress[J].J Geophys Res,100:18205~18228
Eric P Chael.1987.Spectral scaling of earthquakesinthe Miramichi region of New Brunswick[J].Bull SeismSoc Amer,77(2):347~365
McGarr A.1999.On relating apparent stress to the stress causing earthquake fault slip[J].J Geophys Res,104:3003~3011
Newman A V,Okal E A.1998.Teleseismic esti mates of radiated seismic energy:TheE/M0discri minant for Tsunamiearthquakes[J].J Geophys Res,103:26885~26898
Pulido N,Irikura K.2000.Esti mation of dynamic rupture parameters from the radiated seismic energy and apparentstress[J].Geophys Res Lett,27:3945~3948
Wyss M,Brune J N.1968.Seismic moment,stress,and source di mensions for earthquakesin the California-Nevada Re-gion[J].J Geophys Res,73(14):4681~4694
Wyss M.1970a.Stress esti mates for South American shallowand deep earthquake[J].J Geophys Res,75(8):1529~1544
Wyss M.1970b.Apparent stresses esti mates of earthquakes on ridges compared to apparent stresses of earthquakes inTrenches[J].Geophys J R astr Soc,19:479~484
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