摘要
地震预警技术(EEW)是目前防震减灾相对有效的方法之一,研究震源破裂初始段波形信息可为EEW系统的震级实时估算提供理论支持。本文结合P波初动波形特征,分别计算日本和中国地震的强震动记录的位移峰值曲线,对比各震级的位移峰值均值曲线的特征,然后利用分段函数模型进行拟合,量化初动上升斜率B1和上升时间T1等特征参数,并统计此类参数与震级相关性。结果表明:当不考虑幅值差异时,随震级的增大,P波初动波形由简单变复杂,均值曲线初始上升段斜率逐级降低,初始上升时间变长,B1等特征参数与震级具有很好的相关性。此外在不同地质构造环境中地震的强震动记录此特征基本一致。因此P波初始段的特征参数可用于估算震级大小,同时证实震源初始破裂过程的信息可反映最终地震的强弱。
Earthquake early warning(EEW) technology is an effective method for earthquake prevention and mitigation. Waveform information in the initial source rupture stage is analyzed to provide theoretical support for the real-time magnitude estimation in the EEW system. In this paper, combining the characteristics of the P-wave initial motion waveform, we calculate displacement peak curves of strong earthquake records selected from earthquake events in Japan and China, compare the characteristics of displacement peak mean curves for magnitude, quantify the characteristic parameters by fitting them with a piecewise function model, such as the initial rising slope B1 and the rising time T1,and calculate statistical correlation of them with magnitude. The results show that with the magnitude increasing the initial P-wave waveform changes from simple to complex when ignoring amplitude difference, the initial rising slope of mean curve is gradually reduced, and the initial rise time becomes longer. At the same time, the quantitative parameters, such as B1, of the initial rising segment have a good correlation with magnitude. In addition, the characteristics of the initial segment in strong motion records selected from different geological tectonic are basically consistent. Therefore, the characteristic parameters of initial P-wave can be used to estimate the magnitude which confirms that the information from the initial source rupture reflect the final earthquake strength.
引文
[1] Nakamura H,Horiuchi S,Wu C,et al.Evaluation of the real-time earthquake information system in Japan[J].Geophys.Res.Lett.,2009,36(5):349-363.
[2] Hoshiba M,Kamigaichi O,Saito M,et al.Earthquake early warning starts nationwide in Japan[J].Eos,Transactions of the American Geophysical Union,2008,89,73-74.
[3] Aranda J M E,Jimenez A,Ibarrola G,et al.Mexico City seismic alert system[J].Seismological Research Letters,1995,66(6):42-53.
[4] Erdik M,Fahjan Y,Ozel O,et al.Istanbul earthquake rapid response and the early warning system[J].Bulletin of Earthquake Engineering,2003,1(1):157-163.
[5] Wu Y M,Teng T.A virtual subnetwork approach to earthquake early warning[J].Bulletin of the Seismological Society of America,2002,92(5):2008-2018.
[6] Zhang H,Jin X,Wei Y,et al.An earthquake early warning system in Fujian,China[J].Bulletin of the Seismological Society of America,2016,106(2):755-765.
[7] Clinton J,Zollo A,Marmureanu A,et al.State-of-the art and future of earthquake early warning in the European region[J].Bulletin of Earthquake Engineering,2016,14(9):2441-2458.
[8] B?se M,Allen R,Brown H,et al.CISN ShakeAlert:An earthquake early warning demonstration system for California[M]//Early warning for geological disasters.Springer,Berlin,Heidelberg,2014:49-69.
[9] Sheen D H,Park J H,Chi H C,et al.The first stage of an earthquake early warning system in South Korea[J].Seismological Research Letters,2017,88(6):1491-1498.
[10] 金星,张红才,李军,等.地震预警震级确定方法研究[J].地震学报,2012,34(5):593-610.JIN Xing,ZHANG Hongcai,LI Jun,et al.Research on earthquake early warning magnitude estimate[J].Acta Seismologica Sinica,2012,34(5):593-610.(in Chinese)
[11] 马强.地震预警技术研究及应用[D].哈尔滨:中国地震局工程力学研究所,2008.MA Qiang.Study and Application on Earthquake Early Warning[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2008.(in Chinese)
[12] Kilb D,Gomberg J.The initial subevent of the 1994 Northridge,California,earthquake:Is earthquake size predictable?[J].Journal of Seismology,1999,3(4):409-420.
[13] Mori J,Kanamori H.Initial rupture of earthquakes in the 1995 Ridgecrest,California sequence[J].Geophysical Research Letters,1996,23(18):2437-2440.
[14] Umeda Y.The bright spot of an earthquake[J].Tectonophysics,1992,211(1-4):13-22.
[15] Ishihara Y,Fukao Y,Yamada I,et al.Rising slope of moment rate functions:the 1989 earthquakes off east coast of Honshu[J].Geophysical Research Letters,1992,19(9):873-876.
[16] Iio Y.Observations of the slow initial phase generated by microearthquakes:Implications for earthquake nucleation and propagation[J].Journal of Geophysical Research:Solid Earth,1995,100(B8):15333-15349.
[17] Ellsworth W L,Beroza G C.Seismic evidence for an earthquake nucleation phase[J].Science,1995,268(5212):851-855.
[18] Ohnaka M.Nonuniformity of the constitutive law parameters for shear rupture and quasistatic nucleation to dynamic rupture:a physical model of earthquake generation processes[J].Proceedings of the National Academy of Sciences,1996,93(9):3795-3802.
[19] Rubin A M,Ampuero J P.Self-similar slip pulses during rate-and-state earthquake nucleation[J].Journal of Geophysical Research:Solid Earth,2009,114(B11).
[20] Colombelli S,Zollo A,Festa G,et al.Evidence for a difference in rupture initiation between small and large earthquakes[J].Nature communications,2014,5:3958.
[21] Noda S.Statistical characterization of P-wave growth for earthquake early warning[J].Quarterly Report of RTRI,2018,59(2):128-134.
[22] 陈运泰,林邦慧,李兴才,等.巧家、石棉的小震震源参数的测定及其地震危险性的估计[J].地球物理学报,1976,1(3):206-231.CHEN Yuntai,LIN Banghui,LI Xingcai,et al.The determination of source parameters for small earthquakes in qiaojia and shimian and the estimation of potential earthquake danger[J].Chinese J.Geophys,1976,1(3):206-231.(in Chinese)
[23] Wu Y M,Zhao L.Magnitude estimation using the first three seconds P-wave amplitude in earthquake early warning[J].Geophysical Research Letters,2006,33(16):L13612.
[24] Ohnaka M,Yamashita T.A cohesive zone model for dynamic shear faulting based on experimentally inferred constitutive relation and strong motion source parameters[J].Journal of Geophysical Research:Solid Earth,1989,94(B4):4089-4104.
[25] Nielsen S,Taddeucci J,Vinciguerra S.Experimental observation of stick-slip instability fronts[J].Geophysical Journal International,2010,180(2):697-702.
[26] Kaneko Y,Ampuero J P.A mechanism for preseismic steady rupture fronts observed in laboratory experiments[J].Geophysical Research Letters,2011,38(21):L21307.
[27] Tinti E,Bizzarri A,Cocco M.Modeling the dynamic rupture propagation on heterogeneous faults with rate and state dependent friction[J].Annals of Geophysics,2005,48(2):327-345.
[28] Uenishi K,Rice J R.Universal nucleation length for slip-weakening rupture instability under nonuniform fault loading[J].Journal of Geophysical Research:Solid Earth,2003,108(B1):2042.
[29] Ampuero J P,Vilotte J P,Sanchez-Sesma F J.Nucleation of rupture under slip dependent friction law:simple models of fault zone[J].Journal of Geophysical Research:Solid Earth,2002,107(B12):2-19.
[30] Beroza G C,Ellsworth W L.Properties of the seismic nucleation phase[J].Tectonophysics,1996,261(1-3):209-227.