用小波-超限率分析提取宁陕台汶川地震体应变异常
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摘要
姑咱台观测的汶川地震应变异常变得越来越显著.同时,在龙门山断裂带的另一端,原来不好判别的宁陕台钻孔体应变观测异常也逐渐清晰起来.利用小波分解和改进的超限率分析方法,可以将细微的地震异常变化精细地提取出来.一般地,小波分解得到的某个带通信号,可以分为正常背景和异常"坏点"两部分.通过对这两部分界线划分的研究,找到了客观、惟一确定超限率分析的阈值的方法.分析结果表明:沿整个汶川地震发震构造带,应变异常影响范围比我们以前知道的大很多;特别是,这种异常变化明显受固体潮影响,这对进一步揭示其机制提供了新的重要线索.
The observed strain anomaly at station GZ has become quite evident.At the other end of Longmenshan Fault,an initially unseen anomaly at station NSH is more and more obvious in the dilatometer recording as the time lapses.By means of wavelet decomposition and the help of a modified Overrun Rate Analysis(ORA),the tiny anomaly can be extracted from the raw data.Generally,a band-passed signal obtained with wavelet decomposition can be divided into two parts: normal "background" and abnormal "bad points".An approach to locate the objective as well as exact distinction between the two parts has been developed for the determinate threshold of ORA.According to the analysis,the extent of strain anomaly along the seismic fault of the Wenchuan Earthquake is much larger than previously recognised.The anomaly is characterized by small pulses in consistence with peaks of Earth Tide,providing a clue to search for its mechanism.
The observed strain anomaly at station GZ has become quite evident.At the other end of Longmenshan Fault,an initially unseen anomaly at station NSH is more and more obvious in the dilatometer recording as the time lapses.By means of wavelet decomposition and the help of a modified Overrun Rate Analysis(ORA),the tiny anomaly can be extracted from the raw data.Generally,a band-passed signal obtained with wavelet decomposition can be divided into two parts: normal "background" and abnormal "bad points".An approach to locate the objective as well as exact distinction between the two parts has been developed for the determinate threshold of ORA.According to the analysis,the extent of strain anomaly along the seismic fault of the Wenchuan Earthquake is much larger than previously recognised.The anomaly is characterized by small pulses in consistence with peaks of Earth Tide,providing a clue to search for its mechanism.
引文
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[3]梅世蓉,冯德益,张国民等.中国地震预报概论.北京:地震出版社,1993.Mei S R,Feng D Y,Zhang G M,et al.Introduction toearthquake prediction in China(in Chinese).Beijing:Seismological Press,1993.
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[5]Qiu Z H,Zhang B H,Huang X N,et al.On the cause ofground stress tensile pulses observed before the 1976Tangshan earthquake.Bull.Seism.Soc.Am.,1988,88(4):989-994.
[6]池顺良,池毅,邓涛等.从5.12汶川地震前后分量应变仪观测到的应变异常看建设密集应变观测网络的必要性.国际地震动态,2009,(1):1-13.Chi S L,Chi Y,Deng T,et al.The necessity of buildingnational strain-observation network from the strain abnormalitybefore Wenchuan earthquake.Recent Developments in WorldSeismology(in Chinese),2009,(1):1-13.
[7]邱泽华,周龙寿,池顺良.用超限率分析法研究汶川地震的前兆应变变化.大地测量与地球动力学,2009,29(4):1-4,9.Qiu Z H,Zhou L S,Chi S L.Study on precursory strainchanges of Wenchuan earthquake with ORA method.Journalof Geodesy and Geodynamics(in Chinese),2009,29(4):1-4,9.
[8]邱泽华,张宝红,池顺良等.汶川地震前姑咱台观测的异常应变变化.中国科学(地球科学),2010,40(8):1040-1047.Qiu Z H,Zhang B H,Chi S L,et al.Abnormal strainchanges observed at Guza before the Wenchuan earthquake.Sci.China(Earth Sci.)(in Chinese),2010,40(8):1040-1047.
[9]陈运泰.地震预测:回顾与展望.中国科学D辑(地球科学),2009,39(12):1633-1658.Chen Y T.Earthquake prediction:Retrospect and prospect.Sci.China Ser.D(Earth Sci.)(in Chinese),2009,39(12):1633-1658.
[10]Daubechies I.Orthonormal bases of compactly supportedwavelets.Communication on Pure and Applied Math.,1988,41(7):990-996.
[11]Mallat S.Multiresolution approximation and wavelets.Transactions of the American Mathematical Society,1992,315:69-88.
[12]Mallat S G.A theory for multiresolution signal decomposition:thewavelet representation signal decomposition.IEEE Trans.onPattern Analysis and Machine Intelligence,1989,11(7):674-693.
[13]Mallat S G.Multiresolution approximations and waveletorthogonal bases of L2.Trans.of American MathematicalSociety,1989,315(1):69-87.
[14]Armstrong B H.Acoustic emission prior to rockbursts andearthquakes.Bull.Seismol.Soc.Amer.,1969,59(3):1259-1279.
[15]Mogi K.Earthquake as acoustic emission-1980IZU PeninsulaEarthquake in particular.J.of Acoust.Emission.,1982,1(1):37-44.
[16]Lockner D A,Byerlee J D,Kuksenko V,et al.Quasi-staticfault growth and shear fracture energy in granite.Nature,1991,350(6313):39-42.
[17]Lockner D.Brittle fracture as an analog to earthquakes:Canacoustic emission be used to develop a viable predictionstrategy.J.Acoust.Emission.,1996,14:S88-S101.
[18]陈颙.不同应力途径三轴压缩下岩石的声发射.地震学报,1981,(1):41-48.Chen Y.Acoustic emission of rocks under triaxialcompression along various stress paths.Acta SeismologicaSinica(in Chinese),1981,(1):41-48.
[19]刘力强,马胜利,马瑾等.岩石构造对声发射统计特征的影响.地震地质,1999,21(4):377-386.Liu L Q,Ma S L,Ma J,et al.Effect of rock structure onstatistic characteristics of acoustic emission.Seismology andGeology(in Chinese),1999,21(4):377-386.
[2]丁国瑜,梅世蓉,马宗晋.地震预报方法.见:丁国瑜,马宗晋主编.国际地震预报讨论会论文选.北京:地震出版社,1981.174-179.Ding G Y,Mei S R,Ma Z J.Methods of earthquakeprediction.∥Ding G Y,Ma Z J,eds.Selected Papers of theInternational Symposium on Earthquake Prediction(inChinese).Beijing:Seismological Press,1981.174-179.
[3]梅世蓉,冯德益,张国民等.中国地震预报概论.北京:地震出版社,1993.Mei S R,Feng D Y,Zhang G M,et al.Introduction toearthquake prediction in China(in Chinese).Beijing:Seismological Press,1993.
[4]李茂玮.乌恰7.4级地震的土层应力前兆.内陆地震,1987,1(1):77-83.Li M W.Precursors of strain in soil before the M7.4 Wuqiaearthquake.Inland Earthquake(in Chinese),1987,1(1):77-83.
[5]Qiu Z H,Zhang B H,Huang X N,et al.On the cause ofground stress tensile pulses observed before the 1976Tangshan earthquake.Bull.Seism.Soc.Am.,1988,88(4):989-994.
[6]池顺良,池毅,邓涛等.从5.12汶川地震前后分量应变仪观测到的应变异常看建设密集应变观测网络的必要性.国际地震动态,2009,(1):1-13.Chi S L,Chi Y,Deng T,et al.The necessity of buildingnational strain-observation network from the strain abnormalitybefore Wenchuan earthquake.Recent Developments in WorldSeismology(in Chinese),2009,(1):1-13.
[7]邱泽华,周龙寿,池顺良.用超限率分析法研究汶川地震的前兆应变变化.大地测量与地球动力学,2009,29(4):1-4,9.Qiu Z H,Zhou L S,Chi S L.Study on precursory strainchanges of Wenchuan earthquake with ORA method.Journalof Geodesy and Geodynamics(in Chinese),2009,29(4):1-4,9.
[8]邱泽华,张宝红,池顺良等.汶川地震前姑咱台观测的异常应变变化.中国科学(地球科学),2010,40(8):1040-1047.Qiu Z H,Zhang B H,Chi S L,et al.Abnormal strainchanges observed at Guza before the Wenchuan earthquake.Sci.China(Earth Sci.)(in Chinese),2010,40(8):1040-1047.
[9]陈运泰.地震预测:回顾与展望.中国科学D辑(地球科学),2009,39(12):1633-1658.Chen Y T.Earthquake prediction:Retrospect and prospect.Sci.China Ser.D(Earth Sci.)(in Chinese),2009,39(12):1633-1658.
[10]Daubechies I.Orthonormal bases of compactly supportedwavelets.Communication on Pure and Applied Math.,1988,41(7):990-996.
[11]Mallat S.Multiresolution approximation and wavelets.Transactions of the American Mathematical Society,1992,315:69-88.
[12]Mallat S G.A theory for multiresolution signal decomposition:thewavelet representation signal decomposition.IEEE Trans.onPattern Analysis and Machine Intelligence,1989,11(7):674-693.
[13]Mallat S G.Multiresolution approximations and waveletorthogonal bases of L2.Trans.of American MathematicalSociety,1989,315(1):69-87.
[14]Armstrong B H.Acoustic emission prior to rockbursts andearthquakes.Bull.Seismol.Soc.Amer.,1969,59(3):1259-1279.
[15]Mogi K.Earthquake as acoustic emission-1980IZU PeninsulaEarthquake in particular.J.of Acoust.Emission.,1982,1(1):37-44.
[16]Lockner D A,Byerlee J D,Kuksenko V,et al.Quasi-staticfault growth and shear fracture energy in granite.Nature,1991,350(6313):39-42.
[17]Lockner D.Brittle fracture as an analog to earthquakes:Canacoustic emission be used to develop a viable predictionstrategy.J.Acoust.Emission.,1996,14:S88-S101.
[18]陈颙.不同应力途径三轴压缩下岩石的声发射.地震学报,1981,(1):41-48.Chen Y.Acoustic emission of rocks under triaxialcompression along various stress paths.Acta SeismologicaSinica(in Chinese),1981,(1):41-48.
[19]刘力强,马胜利,马瑾等.岩石构造对声发射统计特征的影响.地震地质,1999,21(4):377-386.Liu L Q,Ma S L,Ma J,et al.Effect of rock structure onstatistic characteristics of acoustic emission.Seismology andGeology(in Chinese),1999,21(4):377-386.
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