地震监测中的电阻率层析技术
|
摘要
将电阻率层析技术应用于地震监测 ,由视电阻率值重建出介质的真电阻率图像 ,取得了较好效果 .在宝坻台和昌黎台设立的两个试验点上于 1 998年 4月 1 4日ML5 .0和ML4 .4唐山两次地震前的 6天左右层析图像出现了明显的异常变化 :宝坻台的电阻率图像一改通常的在平稳背景上叠加小量随机变化的特点 ,出现了一种有序性特征的新图样 ;昌黎台也出现了反差加大、高低阻区集中分布的有序性特征 .上述异常图样均在震后消失 .层析图像在震前出现的熵值降低可能是这次地震活动的前兆 .地层导电结构和孔隙度的变化 ,是引起电阻率异常的直接原因 .研究表明 ,常规的单一极距的视电阻率测量之所以对真电阻率的变化不敏感且丧失空间分辨能力 ,是由于该物理量同时具有积分值和位函数这两个固有特征所决定的 .在地震监测中 ,改造现行观测系统 ,引入层析成像 ,是发展技术的方向 .
Resistivity tomography was applied to earthquake monitoring in the present study. Through inversion for apparent resistivity, the image of true resistivity was reconstructed. This method well reveals the nature of the variation of the relevant physical parameters during seismogenic process. At two stations in North China, Baodi and Changli, obvious anomalous changes appeared in the tomograms 6 days before the occurrence of two earthquakes with M L5.0 and M L4.4, respectively, in Tangshan on 14 April 1998. The distribution of true resistivity in the images of Baodi station showed a new pattern, i.e. an ordered state, instead of an ordinarily stable pattern with an even background. The resistivity image of Changli station showed distinct high and low resistivity areas and an ordered pattern, too. After these earthquakes, the above mentioned phenomena all disappeared, while the basic image pattern relating to geological structure beneath the stations did not change much. As an indicator of the ordered state of an image, the entropy of tomograms at two stations all decreased distinctly before the earthquakes, which might be the precursors to these earthquakes. It is inferred that the present resistivity anomalies were mainly attributed to the changes of the electrical conducting structure and porosity in the soil layer under increasing tectonic stress before earthquakes. The present result shows that in a conventional apparent resistivity survey with one fixed electrode spacing the observational results are not sensitive to the change of true resistivity and have not basic spatial resolution. These shortcomings result from an essential property of apparent resistivity being both an integral value and potential function. Adopting resistivity tomography in the earthquake monitoring has become necessary to improve our present observational system.
Resistivity tomography was applied to earthquake monitoring in the present study. Through inversion for apparent resistivity, the image of true resistivity was reconstructed. This method well reveals the nature of the variation of the relevant physical parameters during seismogenic process. At two stations in North China, Baodi and Changli, obvious anomalous changes appeared in the tomograms 6 days before the occurrence of two earthquakes with M L5.0 and M L4.4, respectively, in Tangshan on 14 April 1998. The distribution of true resistivity in the images of Baodi station showed a new pattern, i.e. an ordered state, instead of an ordinarily stable pattern with an even background. The resistivity image of Changli station showed distinct high and low resistivity areas and an ordered pattern, too. After these earthquakes, the above mentioned phenomena all disappeared, while the basic image pattern relating to geological structure beneath the stations did not change much. As an indicator of the ordered state of an image, the entropy of tomograms at two stations all decreased distinctly before the earthquakes, which might be the precursors to these earthquakes. It is inferred that the present resistivity anomalies were mainly attributed to the changes of the electrical conducting structure and porosity in the soil layer under increasing tectonic stress before earthquakes. The present result shows that in a conventional apparent resistivity survey with one fixed electrode spacing the observational results are not sensitive to the change of true resistivity and have not basic spatial resolution. These shortcomings result from an essential property of apparent resistivity being both an integral value and potential function. Adopting resistivity tomography in the earthquake monitoring has become necessary to improve our present observational system.
引文
[1] 杜学彬,薛顺章,郝 臻等.地电阻率中短期异常与地震的关系.地震学报,2000,22(4):368—376.DUXueBin,XUEShunZhang,HAOZhen,etal.Ontherelationofmoderate shorttermanomalyofearthresistivityofearth quake.ActaSeismologicaSinica(inChinese),2000,22(4):368—376.
[2] 王志贤,张学民,李永庆等.地电中期前兆异常特征及其对强震中期趋势的判断.地震学报,1999,21(2):187—193.WANGZhiXian,ZHANGXueMin,LIYongQing,etal.Medium shottermprecursoranomalycharacteristicsofgeoelec trivityandthejudgmentofmediumtermtrendtostrongshocks.ActaSeimologicaSinica(inChinese),1999,21(2):187—193.
[3] 钱家栋,陈有发,金安忠.地电阻率法在地震预报中的应用.北京:地震出版社,1985.1—274.QIANJiaDong,CHANYouFa,JINAnZhong.ApplicationofGeoelectrivitytoEarthquakePrediction.Beijing:Seismologi calPress,1985.1—274.
[4] 钱复业,赵玉林.地震前地电阻率变化十例.地震学报,1980,2(2):186—197.QIANFuYe,ZHAOYuLin.Tenexamplesofchangesinearth resistivitypriortostrongearthquakes.ActaSeismologicaSini ca(inChinese),1980,2(2):186—197.
[5] ShimaH ,Two dimensionalautomaticresistivityinversiontechniqueusingalphacenters,Geophysics,1990,55:628—694.
[6] 李晓芹,陶裕录,冯 锐.电阻率层析成像的原理与初步应用.地震地质,1998,20(3):234—242.LIXiaoQin,TAOYuLu,FENGRui.Principlesofresistivitytomographyandpreliminaryapplication.SeismologyandGeol ogy(inChinese),1998,20(3):234—242.
[7] 冯 锐,李晓芹,陶裕录等.电阻率层析成像用于水文地质勘探.地震学报,1997,19(6):655—663.FENGRui,LIXiaoQin,TAOYuLu.ElectricresistanceCTusedinhydrogeologicprospecting.ActaSeismologicaSinica(inChinese),1997,19(6):655—663.
[8] UshijimaK ,MizunagaH ,FuruyaS ,etal.FluidflowtomographysurveyinTakigamigeothermalfield,Geotomography.In:Asakura,N .ed.,SEGJIntern.Pub.No.2,SEGJ,Tokyo,1992,2:247—260.
[9] DiMaioR ,MaurielloP ,PatellaD ,etal.Self potential,geoelectricandmagnetotelluricstudiesinItalianactivevolcanicar eas,AnnaliDiGeofisica,1997,XL(2):519—537.
[10] LapennaV ,PatellaD ,PiscitelliS,Tomographicanalysisofself potentialdatainaseismicareaofSouthernItaly,AnnaliDiGeofisica,2000,43(2):361—373.
[11] 罗延钟,张桂青.电子计算机在电法勘探中的应用.武汉:武汉地质学院出版社,1987.LUOYanZhong,ZHANGGuiQin.Applicationofcomputertechniquestoelectricprospecting.Wuhan:PressofGeologyCollege(Wuhan),1987.
[12] 傅良魁.电法勘探教程.北京,地质出版社,1990.FULiangKui.ElectricProspecting.Beijing:GeologicalPublishingHouse,1990.
[13] 侯康明,杜学彬.偶极电测深法预报地震的试验研究.华北地震科学,1993,11(1):74—83.HOUKangMing,DUXueBin.Experimentofelectricdipolesoundinginearthquakeprediction.NorthChinaEarthquakeSciences(inChinese),1993,11(1):74—83.
[14] 薛顺章,温新民,董永德等.地电阻率预报地震新方法的研究.地震学报,1994,16(2):227—234.XUEShunZhang,WENXinMin,DONGYongDe,etal.Studyofanewmethodforearthquakepredictionbyearth resistivi tymeasurements.ActaSeismologicaSinica(inChinese),1994,16(2):227—234.
[15] 钱家栋,赵和云.地电阻率的数值模拟和多极距观测系统.地震学报,1988,10(1):77—89.QIANJiaDong,ZHAOHeYun.Earthresistivitymodelingandobservationalsystemwithmulti seperationofelectrodes.ActaSeismologicaSinica(inChinese),1988,10(1):77—89.
[16] Zodhy,AAR .AnewmethodfortheinterpretationofSchlumbergerandWennersoundingcurves.Geophysics,1989,54:245—253.
[17] 张德信,王文礼等.我国部分地电台基本情况表.见:钱复业等主编,地震预报-地电方法论文集,福州:福建科学技术出版社,1985,318—321.ZHANGDeXing,WANGWen li,etal.Basicinformationofearth resistivitystationsinChina.In:QIANFu ye,etal.ed.EarthquakePredictionandGeoelectricity(inChinese).Fuzhou:FujianScienceandTechnologyPress,1985,318—321.
[18] 刘小伟,黄金瑛,王 玲.地电阻率观测资料评定方法和地电断面的模型计算.钱复业等主编,地震预报———地电方法论文集,福州:福建科学技术出版社,1985,145—151.LIUXiaoWei,HUANGJinYing,WANGLing.Evaluationofgeoelectricalobservationaldataandmodelingofgeoelectricalsection.In:QIANFu ye,etal.ed.EarthquakePredictionandGeoelectricity(inChinese).Fuzhou:FujianScienceandTechnologyPress,1985,145—151.
[19] 徐世浙.视电阻率年变的定量计算.地震学报,1985,7(4):422—427.XUShiZhe.Quantitativecalculationoftheannualvariationofapparentresistivity.ActaSeismologicaSinica(inChinese),1985,7(4):422—427.
[20] 普拉特WK .数字图像处理学.高荣坤等译,北京:科学出版社,1984.PrattWK .DigitalImageProcessing.TranslatedbyGAORongKun,etal.Beijing:SciencePress,1984.
[21] FENGR ,SUNCC ,TAOYL .Electromagnetictomographyrelatedtoearthquakes.In:HayakawaM ,ed.AtmosphericandIonosphericElectromagneticPhenomenaAssociatedwithEarthquakes.Tokyo:TerraScientificPub.Co.,1999,245—254.
[22] 郝锦绮,冯 锐,李晓芹等.对样品含水结构的电阻率CT研究.地震学报,2000,22(3):305—309.HAOJinQi,FENGRui,LIXiaoQin.Resistivitytomographystudyonsampleswithwater bearingstructure.ActaSeismolog icaSinica(inChinese),2000,22(3):305—309.
[23] 郝锦绮,冯 锐,周建国等.对岩石破裂过程中电阻率变化机理的探讨.地球物理学报,2002,(待发表)HAOJinQi,FENGRui,ZHOUJianGuo,etal.Studyonthemechanismofresistivitychangeduringrockfracturing.Chi neseJ.Geophys.(inChinese),2002,(inpress).
[2] 王志贤,张学民,李永庆等.地电中期前兆异常特征及其对强震中期趋势的判断.地震学报,1999,21(2):187—193.WANGZhiXian,ZHANGXueMin,LIYongQing,etal.Medium shottermprecursoranomalycharacteristicsofgeoelec trivityandthejudgmentofmediumtermtrendtostrongshocks.ActaSeimologicaSinica(inChinese),1999,21(2):187—193.
[3] 钱家栋,陈有发,金安忠.地电阻率法在地震预报中的应用.北京:地震出版社,1985.1—274.QIANJiaDong,CHANYouFa,JINAnZhong.ApplicationofGeoelectrivitytoEarthquakePrediction.Beijing:Seismologi calPress,1985.1—274.
[4] 钱复业,赵玉林.地震前地电阻率变化十例.地震学报,1980,2(2):186—197.QIANFuYe,ZHAOYuLin.Tenexamplesofchangesinearth resistivitypriortostrongearthquakes.ActaSeismologicaSini ca(inChinese),1980,2(2):186—197.
[5] ShimaH ,Two dimensionalautomaticresistivityinversiontechniqueusingalphacenters,Geophysics,1990,55:628—694.
[6] 李晓芹,陶裕录,冯 锐.电阻率层析成像的原理与初步应用.地震地质,1998,20(3):234—242.LIXiaoQin,TAOYuLu,FENGRui.Principlesofresistivitytomographyandpreliminaryapplication.SeismologyandGeol ogy(inChinese),1998,20(3):234—242.
[7] 冯 锐,李晓芹,陶裕录等.电阻率层析成像用于水文地质勘探.地震学报,1997,19(6):655—663.FENGRui,LIXiaoQin,TAOYuLu.ElectricresistanceCTusedinhydrogeologicprospecting.ActaSeismologicaSinica(inChinese),1997,19(6):655—663.
[8] UshijimaK ,MizunagaH ,FuruyaS ,etal.FluidflowtomographysurveyinTakigamigeothermalfield,Geotomography.In:Asakura,N .ed.,SEGJIntern.Pub.No.2,SEGJ,Tokyo,1992,2:247—260.
[9] DiMaioR ,MaurielloP ,PatellaD ,etal.Self potential,geoelectricandmagnetotelluricstudiesinItalianactivevolcanicar eas,AnnaliDiGeofisica,1997,XL(2):519—537.
[10] LapennaV ,PatellaD ,PiscitelliS,Tomographicanalysisofself potentialdatainaseismicareaofSouthernItaly,AnnaliDiGeofisica,2000,43(2):361—373.
[11] 罗延钟,张桂青.电子计算机在电法勘探中的应用.武汉:武汉地质学院出版社,1987.LUOYanZhong,ZHANGGuiQin.Applicationofcomputertechniquestoelectricprospecting.Wuhan:PressofGeologyCollege(Wuhan),1987.
[12] 傅良魁.电法勘探教程.北京,地质出版社,1990.FULiangKui.ElectricProspecting.Beijing:GeologicalPublishingHouse,1990.
[13] 侯康明,杜学彬.偶极电测深法预报地震的试验研究.华北地震科学,1993,11(1):74—83.HOUKangMing,DUXueBin.Experimentofelectricdipolesoundinginearthquakeprediction.NorthChinaEarthquakeSciences(inChinese),1993,11(1):74—83.
[14] 薛顺章,温新民,董永德等.地电阻率预报地震新方法的研究.地震学报,1994,16(2):227—234.XUEShunZhang,WENXinMin,DONGYongDe,etal.Studyofanewmethodforearthquakepredictionbyearth resistivi tymeasurements.ActaSeismologicaSinica(inChinese),1994,16(2):227—234.
[15] 钱家栋,赵和云.地电阻率的数值模拟和多极距观测系统.地震学报,1988,10(1):77—89.QIANJiaDong,ZHAOHeYun.Earthresistivitymodelingandobservationalsystemwithmulti seperationofelectrodes.ActaSeismologicaSinica(inChinese),1988,10(1):77—89.
[16] Zodhy,AAR .AnewmethodfortheinterpretationofSchlumbergerandWennersoundingcurves.Geophysics,1989,54:245—253.
[17] 张德信,王文礼等.我国部分地电台基本情况表.见:钱复业等主编,地震预报-地电方法论文集,福州:福建科学技术出版社,1985,318—321.ZHANGDeXing,WANGWen li,etal.Basicinformationofearth resistivitystationsinChina.In:QIANFu ye,etal.ed.EarthquakePredictionandGeoelectricity(inChinese).Fuzhou:FujianScienceandTechnologyPress,1985,318—321.
[18] 刘小伟,黄金瑛,王 玲.地电阻率观测资料评定方法和地电断面的模型计算.钱复业等主编,地震预报———地电方法论文集,福州:福建科学技术出版社,1985,145—151.LIUXiaoWei,HUANGJinYing,WANGLing.Evaluationofgeoelectricalobservationaldataandmodelingofgeoelectricalsection.In:QIANFu ye,etal.ed.EarthquakePredictionandGeoelectricity(inChinese).Fuzhou:FujianScienceandTechnologyPress,1985,145—151.
[19] 徐世浙.视电阻率年变的定量计算.地震学报,1985,7(4):422—427.XUShiZhe.Quantitativecalculationoftheannualvariationofapparentresistivity.ActaSeismologicaSinica(inChinese),1985,7(4):422—427.
[20] 普拉特WK .数字图像处理学.高荣坤等译,北京:科学出版社,1984.PrattWK .DigitalImageProcessing.TranslatedbyGAORongKun,etal.Beijing:SciencePress,1984.
[21] FENGR ,SUNCC ,TAOYL .Electromagnetictomographyrelatedtoearthquakes.In:HayakawaM ,ed.AtmosphericandIonosphericElectromagneticPhenomenaAssociatedwithEarthquakes.Tokyo:TerraScientificPub.Co.,1999,245—254.
[22] 郝锦绮,冯 锐,李晓芹等.对样品含水结构的电阻率CT研究.地震学报,2000,22(3):305—309.HAOJinQi,FENGRui,LIXiaoQin.Resistivitytomographystudyonsampleswithwater bearingstructure.ActaSeismolog icaSinica(inChinese),2000,22(3):305—309.
[23] 郝锦绮,冯 锐,周建国等.对岩石破裂过程中电阻率变化机理的探讨.地球物理学报,2002,(待发表)HAOJinQi,FENGRui,ZHOUJianGuo,etal.Studyonthemechanismofresistivitychangeduringrockfracturing.Chi neseJ.Geophys.(inChinese),2002,(inpress).
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心