2001年2～4月强地震的前兆次声波测量研究
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摘要
介绍强地震前兆观测的一种新方法—次声波法 .在北京昌平安装次声三点阵 ,并测量到2 0 0 1年 2～ 4月强地震的前兆次声波P t曲线、波向和水平波速图及其三维动态频谱 .连续一年多的测量结果表明 :(1)强震前约 10天内常能测到振幅很强、方向可测的地震前兆次声 .其三维动态频谱的特点是 :振幅由弱 (10～ 2 0Pa)逐渐加强到 (40～ 80Pa)或更大 ;最后的周期范围很宽 (2～ 6 5分 ) ;波形明显不同于流星雨次声、大风次声和雷次声 .(2 )该三维动态频谱的最大振幅不仅受震级大小影响 ,而且与震源距离、深度及其它因素都有关 .(3)初步解释了强震前兆次声的产生机理和传播机制 .(4)若两个相距足够远的三点阵所测波向相交 ,可预测震中位置 .故进一步测量研究地震前兆次声波 ,有可能发展成为临震预报中一种较有效的新方法
A new method about measurement of the precursory infrasonic waves of strong earthquake was introduced. A tripartite array was arranged in Changping, Beijing. The infrasonic signals (the P t curve, the direction and horizontal projection of downward velocity of the wave) stimulated by strong earthquakes during February April 2001 were observed. With fast Fourier transformation, the three dimensional dynamic frequency spectra were obtained. The results over a year are as follows∶ (1) 10 days or so before the occurrence of strong earthquake, the precursory infrasound of the earthquake with strong amplitude and measurable direction can often be measured. The characteristics of the spectrum are∶ the amplitudes of precursory infrasound increase from weak (10～20Pa) to strong (40～80Pa) or even stronger; the final periods become very wide (2～65min); their waveforms are distinctly different from those of meteor shower, strong wind and thunder. (2) The maximal amplitude of the spectrum of the precursory infrasound measured is related not only to the magnitude of earthquake, but also to the distance and the depth of the epicenter as well as some other factors. (3) The generating mechanism of the precursory infrasound of earthquake is that the long period deformational waves produced by pre slips before stick slips or crack propagation before rupture transmit to the atmosphere. The propagation of the precursory infrasound is because its attenuation is extremely small. Besides, sound waveguide of lower channel in the atmospheric layer plays an active role. (4) If the directions of two remote tripartite arrays intersect, the location of the epicenter can be predicted. Therefore the measure of the precursory infrasound could become a new and more effective method of the imminent prediction of strong earthquake.
A new method about measurement of the precursory infrasonic waves of strong earthquake was introduced. A tripartite array was arranged in Changping, Beijing. The infrasonic signals (the P t curve, the direction and horizontal projection of downward velocity of the wave) stimulated by strong earthquakes during February April 2001 were observed. With fast Fourier transformation, the three dimensional dynamic frequency spectra were obtained. The results over a year are as follows∶ (1) 10 days or so before the occurrence of strong earthquake, the precursory infrasound of the earthquake with strong amplitude and measurable direction can often be measured. The characteristics of the spectrum are∶ the amplitudes of precursory infrasound increase from weak (10～20Pa) to strong (40～80Pa) or even stronger; the final periods become very wide (2～65min); their waveforms are distinctly different from those of meteor shower, strong wind and thunder. (2) The maximal amplitude of the spectrum of the precursory infrasound measured is related not only to the magnitude of earthquake, but also to the distance and the depth of the epicenter as well as some other factors. (3) The generating mechanism of the precursory infrasound of earthquake is that the long period deformational waves produced by pre slips before stick slips or crack propagation before rupture transmit to the atmosphere. The propagation of the precursory infrasound is because its attenuation is extremely small. Besides, sound waveguide of lower channel in the atmospheric layer plays an active role. (4) If the directions of two remote tripartite arrays intersect, the location of the epicenter can be predicted. Therefore the measure of the precursory infrasound could become a new and more effective method of the imminent prediction of strong earthquake.
引文
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[20] GeorgesTM .HFDopplerstudiesoftravelingionosphericdisturbances[J].J.Atmos.Terr.Phys.,1968,30∶735.
[21] 谢金来,杨训仁.美国航天飞机”挑战者号”爆炸时所产生的次声波[J].声学学报,1986,11(3):189.
[22] YangXunRen,XieJinLai.DetectionandanalysisoftheinfrasonicwavesattachedtothetragicexplosionofU .S .spaceshuttle“Challenger”[J].JournalofLowFrequencyNoiseandVibration,1986,5(3)∶100～103.
[2] VolodichevN ,PanasjukM .Neutronflashesmayforecastearthquakes.PhysicsWeb,IOPPublishingLtd.,Feb.2001,Article4of15.
[3] 李均之,夏雅琴,陈维生.近几年日本强地震的临震前兆信息[J].北京工业大学学报,1995,21(4):1～12.
[4] 李志雄,高荣胜.1997年新疆伽师几次中强地震的短临预报过程[J].地震,1997,17(3):327～330.
[5] 苏 日方,苏 骁.强地震临震预报的前兆次声测量研究[J].石油大学学报,2000,24(6):106～112.
[6] 苏 日方,苏 骁.1998年11月17日狮子座流星雨的次声观测[J].应用声学,2000,19(3):1～6.
[7] 谢金来,谢照华.1993年7月2日日本北海道地震次声波[J].声学学报,1996,21(1):55～61.
[8] 屠 焰,赵树卿.奇异的次声[M].北京:科学出版社,1979,a)40～42,b)42～45,c)49～51,d)3.
[9] 马宗晋,傅征祥,张郢珍,等.1966-1976年中国九大地震[M].北京:地震出版社,1982,126～127.
[10] 施志远.动物预报地震的奥秘[M].北京:科学普及出版社,1993,42,50～51.
[11] Dieterich,JH .Time dependentfrictionandthemechanicsofstick slip[J].PureApplGeophys,1978,116∶790～806.
[12] Dieterich,JH .Earthquakenucleationonfaultswithrateandstatedependentstrength[J].Tectonophysics,1992,211∶115～134.
[13] RiceJR ,RuinaAL .Stabilityofsteadyfrictionalslipping[J].JApplMech,1983,50∶343～349.
[14] OhnakaM .Earthquakesourcenucleation∶aphysicalmodelforshort-termprecursors[J].Tectonophysics,1992,211∶149～178.
[15] 冯德益,潘琴龙,郑斯华,等.长周期形变波及其所反应的短期和临震地震前兆[J].地震学报,1984,6(1):41～56.
[16] 李世愚,刘万琴,郑治真,等.房山矿震震前井下长周期事件记录的分析[A].见:主编.中国地震学会第七次学术大会论文摘要集[C].北京:地震出版社,1998,120.
[17] HillDP ,FischerKM ,Lahretal.Earthquakesoundsgeneratedbybody wavesgroundmotion[J].Bull.Seism.Soc.Am.,1976,66(4)∶1157～1172.
[18] 李建国,刘祖沅,陈献程.浙江湖南镇水库1982年5月22日3.1级地震序列的近场地声观测和初步研究[J].地震学报,1985,7(3):314～324.
[19] 何祚镛,赵玉芳.声学理论基础[M].北京:国防工业出版社,1981,67～70.
[20] GeorgesTM .HFDopplerstudiesoftravelingionosphericdisturbances[J].J.Atmos.Terr.Phys.,1968,30∶735.
[21] 谢金来,杨训仁.美国航天飞机”挑战者号”爆炸时所产生的次声波[J].声学学报,1986,11(3):189.
[22] YangXunRen,XieJinLai.DetectionandanalysisoftheinfrasonicwavesattachedtothetragicexplosionofU .S .spaceshuttle“Challenger”[J].JournalofLowFrequencyNoiseandVibration,1986,5(3)∶100～103.
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