汶川地震深层地下水位临震异常
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摘要
针对短临地震预报难尤其是临震预报难问题,以2008年汶川地震为背景,对受地震影响严重的川、滇、陕、甘、渝5个省市区域内的深层地下水位进行了分析,发现在龙门山断裂带所在的四川省及其NE方向的甘肃省区域,共有7口井水位表现为明显的临震异常,异常形态包括振荡型、脉冲型和阶升型。利用小波变换方法对振荡型及脉冲型异常进行分析,结果表明:临夏、古浪横梁和清水等井水位信号中存在着周期为2～8 min,振幅为5～59 mm的前驱波波形,这是由于震源体慢破裂过程中发出的地震波造成的。阶升型异常幅度较大,分别为129.4 cm和340.8 cm,从震前几分钟一直持续到震后,未恢复到震前状态;表明引起震时地下水剧烈变化的动力作用在震前已经开始,震时变化只是在此基础上进一步发展与加剧。
Due to middle-term and impending anomaly forecast of earthquake is relatively difficult,taking Wenchuan earthquake in 2008 as the studying background,choosing the severely affected areas such as Sichuan,Yunnan,Shaanxi,Gansu and Chongqing Province/City as study region,the deep groundwater-level anomaly characteristic was analyzed in this study.In Sichuan region,where Longmen Mountain fault locates,and Gansu region along NE direction of Longmen Mountain fault,seven wells groundwater-level appeared clear impending ano-maly,including oscillatory type,pulse type and step type.By wavelet transformation analysis to oscillation and pulse anomaly of groundwater level,the results showed that Linxia,Gulanghengliang,Qingshui well water-levels exist similar precursor waveform,with a cycle of 2-8 min and an anomaly amplitude 5-59 mm.They were the results of seismic wave from source slow rupture of source body,indicating the coming of large earthquake.On the other hands,step-type anomaly amplitudes were relatively large,respectively 129.4 cm and 340.8 cm.They last from a few minutes before earthquake to after earthquake,and couldn't recover the state before earthquake.It showed that the driving function,which caused dramatic changes of groundwater-level,had begun before earthquake,and their coseismic anomaly were further developed and intensified on the basis of it.
Due to middle-term and impending anomaly forecast of earthquake is relatively difficult,taking Wenchuan earthquake in 2008 as the studying background,choosing the severely affected areas such as Sichuan,Yunnan,Shaanxi,Gansu and Chongqing Province/City as study region,the deep groundwater-level anomaly characteristic was analyzed in this study.In Sichuan region,where Longmen Mountain fault locates,and Gansu region along NE direction of Longmen Mountain fault,seven wells groundwater-level appeared clear impending ano-maly,including oscillatory type,pulse type and step type.By wavelet transformation analysis to oscillation and pulse anomaly of groundwater level,the results showed that Linxia,Gulanghengliang,Qingshui well water-levels exist similar precursor waveform,with a cycle of 2-8 min and an anomaly amplitude 5-59 mm.They were the results of seismic wave from source slow rupture of source body,indicating the coming of large earthquake.On the other hands,step-type anomaly amplitudes were relatively large,respectively 129.4 cm and 340.8 cm.They last from a few minutes before earthquake to after earthquake,and couldn't recover the state before earthquake.It showed that the driving function,which caused dramatic changes of groundwater-level,had begun before earthquake,and their coseismic anomaly were further developed and intensified on the basis of it.
引文
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[3]车用太,鱼金子,张淑良,等.山西朔州井水位的“前驱波”记录及其讨论[J].地震学报,2002,24(2):210-216.CHE Yong-tai,YU Jin-zi,ZHANG Shu-liang,et al.Therecords of waterlevel“precursors”and their discussionin well[J].Acta Seismologica Sinica,2002,24(2):210-216.
[4]付虹,邬成栋,刘强,等.印尼巨大地震引起的云南水位异常记录及其意义[J].地震地质,2007,29(4):873-881.FU Hong,WU Cheng-dong,LIU Qiang,et al.Abnormalwater level records caused by Indonesia large earthquakesin Yunnan and its significance[J].Seismology and Geo-logy,2007,29(4):873-881.
[5]敬少群,王佳卫,童迎世,等.小波变换在少震、弱震区地下水位数据分析中的应用[J].华南地震,2002,22(2):9-15.JING Shao-qun,WANG Jia-wei,TONG Ying-shi,et al.The application of wavelet transform to the process of wa-ter level observational data for weak earthquake region[J].South China Journal of Seismology,2002,22(2):9-15.
[6]陈大庆,胡江辉.小波变换在数字化水位观测资料分析中的应用[J].华南地震,2008,28(4):75-81.CHEN Da-qing,HU Jiang-hui.Application of wavelettransform to analysis of water level digital observation data[J].South China Journal of Seismology,2008,28(4):75-81.
[7]周龙寿,邱泽华,唐磊.汶川8.0级地震前驱波的统计检验[J].大地测量与地球动力学,2009,29(2):24-28.ZHOU Long-shou,QIU Ze-hua,TANG Lei.Statisticaltest of precursory waves before Wenchuan Ms8.0 earth-quake[J].Journal of Geodesy and Geodynamics,2009,29(2):24-28.
[8]Mallat S.A theory for multiresolution signal decomposi-tion:the wavelet representation[J].IEEE Transactionson Pattern Analysis and Machine Intelligence,1989,11(7):674-693.
[9]黄声享,尹晖,蒋征.变形监测数据处理[M].武汉:武汉大学出版社,2003.HUANG Sheng-xiang,YIN Hui,JIANG Zheng.Defor-mation monitoring and data processing[M].Wuhan:Wuhan University Press,2003.
[10]Daubechies I.The wavelets transform,time frequencylocalization and signal analysis[J].IEEE Trans on InfoTheory,1990,36(5):961-1005.
[11]张淑亮,程紫燕,唐垒黎,等.井水位前驱波现象与震源成核之间关系的研究[J].中国地震,2008,24(2):159-170.ZHANG Shu-liang,CHENG Zi-yan,TANG Lei-li,etal.Study on relationship between precursor phenomenaof well water level and seismic source nucleation[J].Earthquake Research in China,2008,24(2):159-170.
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