天祝大地电场异常与1995年永登5.8、1996年天祝5.4级地震
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摘要
利用中法合作的天祝电测台从 1 994年 1 0月至 1 997年 6月每分钟的观测资料 ,使用常规分析方法、分数维方法、垂直极化方向投影法和MT定点测深二维反演方法处理后 ,发现在 1 995年 7月 2 2日永登 5.8级地震 (Δ=84km)和 1 996年 6月 1日天祝 5.4级地震 (Δ =65km)前 ,4种方法、5种参数不同程度地显现出短临异常 ,并表现出较好的协调性 .其中分数维异常和主轴视电阻率异常显示了明显的方向性 .地电场异常对与台站同处一条断裂带上天祝地震的孕震过程反映更敏感 .还从 4个方面讨论了异常的可靠性 ,并提出了产生异常的可能机理 .认为永登 5.8级地震前大地电场异常由主要是震源处的电磁辐射以及台站下方 7km左右介质电性变化共同产生 ;而天祝地震前异常主要由台站下方 5～ 3 0km范围内沿断裂走向的岩石电阻率变化所致 .
After processing the data of geoelectric field and geomagnetic component from Tianzhu sino France coorperate station in Oct.1994 to Jun.1997,with methods of mean value analysis,fractional dimension,vertical polarization direction projection and two dimension inversion of fixed set MT, it is found out that the 5 parameters in the 4 methods take on short impending anormalies in different extent before Yongdeng M S 5.8 earthquake (Δ=84 km) on July 22,1995 and Tianzhu M S 5.4 earthquake (Δ=65 km) on June 1,1996.All these anormalies show good coordination,and the fractional dimension and principal axis apparent resistivity anormalies show clear orientation.The anormalies of geoelectric field is more sensitive to the earthquake preparation process of Tianzhou event which took place on the same fault with the station.The anormaly reliability is discussed from 4 points and the anormaly possible mechanism is given. It is suggested that the geoelectric anormaly before Yongdeng M S5.8 earthquake is produced mainly by the focus electromagnetic radiation,comline with electric property variation of medium under the station at depth of 7 km,while before Tianzhu M S5.4 earthquake mainly by the resistivity variation of rock along the fault strike at depth of 5～30 km under the station .
After processing the data of geoelectric field and geomagnetic component from Tianzhu sino France coorperate station in Oct.1994 to Jun.1997,with methods of mean value analysis,fractional dimension,vertical polarization direction projection and two dimension inversion of fixed set MT, it is found out that the 5 parameters in the 4 methods take on short impending anormalies in different extent before Yongdeng M S 5.8 earthquake (Δ=84 km) on July 22,1995 and Tianzhu M S 5.4 earthquake (Δ=65 km) on June 1,1996.All these anormalies show good coordination,and the fractional dimension and principal axis apparent resistivity anormalies show clear orientation.The anormalies of geoelectric field is more sensitive to the earthquake preparation process of Tianzhou event which took place on the same fault with the station.The anormaly reliability is discussed from 4 points and the anormaly possible mechanism is given. It is suggested that the geoelectric anormaly before Yongdeng M S5.8 earthquake is produced mainly by the focus electromagnetic radiation,comline with electric property variation of medium under the station at depth of 7 km,while before Tianzhu M S5.4 earthquake mainly by the resistivity variation of rock along the fault strike at depth of 5～30 km under the station .
引文
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[28]赵和云,阮爱国,梁子斌,等.Pb-PbCL2固体不极化电极在地电场观测中的作用和效能[J].地震,1998,18(增刊):46-52.
[29]赵和云,阮爱国,扬荣,等.天祝地电场三年观测资料的分析和讨论[A].见:地震地电学发展与展望[C].兰州:兰州大学出版社,1998.123-137
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[32]钱书清,郭自强,郭子祺,等.岩石在剪切破裂中的电磁特征[Z].见:中国地震学会第六次学术大会论文摘要集[C].北京:地震出版社,1996.272.
[2]CressGO ,BradyBT ,RowellGA .Sourceofelectromagneticradiationfromfractureofrocksamplesinthelaboratory[J].Geophys.Res.Lett.,14:331—334.
[3]BradyBT ,RowellA .Laboratoryinvestigationoftheelectrodynamicsofrockfracture[J].Nature,1989,321(29):448—492.
[4]MartellG ,SmithPN ,WoodwardAJ.Light,radiofrequencyemissionandionizationeffectsassociatedwithrockfracture[J].Geophys.J.Int.,1989,98:397—401.
[5]YamadaI ,MasudaK ,MizutaniH .Electromagneticandacousticemissionassociatedwithrockfracture[J].Phys.EarthPlanetInter.,1989,57:157-168.
[6]NitsanU .Electromagneticemissionaccompanyingfractureofquartz-bearingrocks[J].Geophys.Res.Lett.,1997,14(8):333-336.
[7]钱书清,等.花岗岩洞爆破时伴随岩石破裂的电磁辐射[J].地球物理学报,26(增刊):887—893.
[8]陈宝华,等.1989,水压致裂过程中的地电效应研究[J].地震学报,1989,11(3):309—318.
[9]ΠерекльманМЕ,ХатиашвилиНГ..破裂电磁辐射理论研究[A].见:萨多夫斯基MA .主编.苏联地震预报研究文集(三)[C].北京:地震出版社,1993.35-39.
[10]钱书清,等.伴随岩石破裂的VLF ,MF ,HF ,和VHF电磁辐射特性的实验研究[J].地震学报,1996,18(3):346—351.
[11]刘煜洲,等.岩石破裂时电磁辐射的影响因素和机理[J].地震学报,1997,19(4):418—425.
[12]金安忠,等.小尺度岩石爆破引起电磁辐射的野外实验观测结果[J].地震学报,1997,19(1):45—50.
[13]钱书清,等.地震电磁辐射前兆不同步现象物理机制的实验研究[J].地震学报,1998,20(5):535-540.
[14]郭自强.岩石破裂中的电声效应[J].地球物理学报,1999,42(1):74-83.
[15]VarotsosP ,AlexopoulosK ,LazaridouM .LatestaspectsofearthquakepredictioninGreecebasedonseismicelectricsignals[J].Tectonophysics(Ⅱ),1993,224(1/3):1-3.
[16]TselentisGA ,IfantisA .Geoelectricvariationsrelatedtoearthquakesobservedduringa3yearindependentinvestigation[J].Geophys.Res.Lett.,1996,23(11):1145—1148.
[17]刘心恒.利用地下电流异常变化预报地震的探讨[J].地震研究,1978,1(3):1—5.
[18]张全喜,等.云南地区中强与强烈地震电磁辐射的观测研究[J].地震学报,14(3):325—331.
[19]张云琳,等.青海共和7.0级地震临震电磁辐射前兆振幅谱的研究[J].地震学报,1993,15(2):186—193.
[20]郝建国,张云福,潘怀文,等.震前极低频电磁异常及频谱特征[J].地震学报,1995,17(1):81—88.
[21]陈宝华,黄声明,杨德英,等.闽台地区震前电磁辐射和自然电位特征的研究[J].地震学报,1996,18(3):404—408.
[22]国家地震局预测预防司.电磁学分析预报的方法[M].北京:地震出版社,1998.192-206.
[23]郝建国,唐天明,李德瑞,等.一种地震短临前兆信息———震前大气电场异常研究[J].地震学报,1998,20(1):101—108.
[24]ΜopozЮΦ,等.梁金仓译.堪察加地震前的大地电流效应[J].世界地震译丛,2000,(4):29—34.
[25]关华平,陈智勇,余素平.首都圈及其邻近地区电磁辐射映震效果研究[J].地震,2000,20(1):65—70.
[26]陈有发,马钦忠,张杰,等.震前自然电场的前兆及可能机理[J].华南地震,1999,19(3):26—34.
[27]毛桐恩,席继楼,王燕琼,等.地震过程中大地电场变化特征[J].地球物理学报,1999,42(4):520—528.
[28]赵和云,阮爱国,梁子斌,等.Pb-PbCL2固体不极化电极在地电场观测中的作用和效能[J].地震,1998,18(增刊):46-52.
[29]赵和云,阮爱国,扬荣,等.天祝地电场三年观测资料的分析和讨论[A].见:地震地电学发展与展望[C].兰州:兰州大学出版社,1998.123-137
[30]阮爱国,赵和云.提取地震地电场异常的垂直极化方向投影法[J].地震学报,2000,22(2):171-175.
[31]ZlotnickiJ ,etal.FrequencyspectralpropertiesofanULFelectromagneticsignalaroundthe21July1995,M =5.7,YongDeng(China)earthquake,Tectonophysic,2001,(待刊).
[32]钱书清,郭自强,郭子祺,等.岩石在剪切破裂中的电磁特征[Z].见:中国地震学会第六次学术大会论文摘要集[C].北京:地震出版社,1996.272.
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