唐山地震前后北京地区地磁场总强度的变化
THE CHANGE OF GEOMAGNETIC TOTAL FIELD IN BEIJING AREA BEFORE AND AFTER THE 1976 TANGSHAN EARTHQUAKE
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摘要: 为了研究1976年唐山地震的磁效应,本文在文献[1]的基础上,利用北京测区六年(1975——1981)的磁测资料,分析了北京地区地磁场长期变化的局部差异,正常(无强震)时期地磁统计量的变化特性,以及长期变化局部差异对地磁统计量的影响.正常时期与地震前后地磁统计量的对比分析表明,唐山地震对北京地区地磁场总强度统计量的影响是显著的.通过不同区域测点、测线的各种组合,计算了地震前后统计量的空间分布,以确定测区信息最强的区域.唐山地震在北京地区所产生的磁效应的统计性质如下:1.异常信息不是短期的波动,而是呈趋势性变化,其持续时间至少一年;2.离震中较近的 S 区异常显著,其主要根据是,地磁统计量 Smj,bsn和Fk2在 S 区变化显著.特别是统计信息的局部差异与长期变化明显不同,前者呈东西分布,后者主要呈北南走向;3.趋势性异常变化的平均空间差异随时间的变化在测区总体并不显著,但在 S 区这种差异的时间变化,在震前1976年3——6月却是显著的.Abstract: In order to study the seismomagnetic effects of the 1976 Tangshan earthquake, the observed data of the geomagnetic total field during the recent six years (1975-1981) have been used in this paper. We have analysed both the local differences of geomagnetic secular variations and the features of changes in geomagnetic statistical parameters in Beijing area during normal period, and the influences of local differences of secular variations on the statistical parameters.Comparison between changes of the parameters in the period before and after the Tangshan earthquake and that in normal period shows that the influence of the Tangshan earthquake on geomagnetic statistical parameters is obvious.In order to determine the portion of the survey network, where the information induced by the Tangshan earthquake was strongest, the space distribution of the statistical parameters before and after the earthquake has been calculated for different kinds of combinations of the points and profiles of observation.The statistical features of seismomagnetic information in the Beijing area caused by the Tangshan earthquake are as follows:1. The anomalous information is not fluctuations in short period but long time changes lasted for one year at least;2. The anomalies in the S region which is closer to the epicenter, were larger, because of the fact that the changes in the geomagnetic statistical parameters Smmj bsn and Fk2 in this region are more obvious, especially, the difference in space distributions of the local statistical information and secular variations, the former trends chiefly east-west while the latter north-south.3. The changes with time in the mean space difference of the tendency of the anomalies is not so clear in the entire surveyed area but becomes quite clear in the region from March to June of 1976, just before the Tangshan earthquake.
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[1] 范国华等,唐山地震对北京地区地磁场总强度的影响,地震学报,1, 1, 39——48,1973,
[2] Stacey, F. D., The Seismomagnetic Effect, Pure Appl. Geophys., 58, 5——22, 1964.
[3] Johnston, M. J. S., Tectonomangetic Effect, Proceedings of The T. Nagata Conference, 283——303,1975.
[4] Rikitake, T., et al., Geomagnetic and Geoelectric Studies of the Matsushiro Earthquake Swarm (4),Bull. Earthq. Res. Inst., 44, 1735——1758, 1966.
[5] Nagata, T., Tectonomagnetism, IAGA Bulletin, 27, 12——43, 1969.
[6] Smith, B. E., et al., A Tectonomagnetic Effect Observed Before a Magnitude 5.2 Earthquake Near Hollister, California, J. G. R., 81, 3556——3603, 1976.
[7] Rikitake, T., et al., Changes in the Geomagnetic Field Associated with Earthquakes in the Izu Penin——sula, Japan, J. G. G., 32, 721——737, 1980.
[8] 祁贵仲等,地磁场的空间相关性及其在地震预报中的应用,地球物理学报,20, 1, 169—— 184, 1977.
[9] Shapiro, V., et al., Anomalous Variations of the Geomagnetic Field in East Faragana——Magnetic Precursor of the Alay Earthquake with M=7.0, G. J. R. Astr. Soc., 68, 1——5, 1982
[10] Shapiro, V., et al., Some Results of the Investigation of Geomagnetic Field Variation in the Urals and Carpathians, G. J. R. Astr. Soc. 66, 1, 71——81, 1981.
[11] Johnston, M., Tectonomagnetic Effects, Earthquake Information Bulletin, 10, 3,82——87,1978.
[12] Nagata, T., Main Characteristics of Recent Geomagnetic Secular Variation,J.G.G., 17, 263——276,1965
[13] 林云芳等,中国华北地区地磁长期变化的分析,地震学报,4, 1, 74——83,1982.[1] 范国华等,唐山地震对北京地区地磁场总强度的影响,地震学报,1, 1, 39——48,1973,
[2] Stacey, F. D., The Seismomagnetic Effect, Pure Appl. Geophys., 58, 5——22, 1964.
[3] Johnston, M. J. S., Tectonomangetic Effect, Proceedings of The T. Nagata Conference, 283——303,1975.
[4] Rikitake, T., et al., Geomagnetic and Geoelectric Studies of the Matsushiro Earthquake Swarm (4),Bull. Earthq. Res. Inst., 44, 1735——1758, 1966.
[5] Nagata, T., Tectonomagnetism, IAGA Bulletin, 27, 12——43, 1969.
[6] Smith, B. E., et al., A Tectonomagnetic Effect Observed Before a Magnitude 5.2 Earthquake Near Hollister, California, J. G. R., 81, 3556——3603, 1976.
[7] Rikitake, T., et al., Changes in the Geomagnetic Field Associated with Earthquakes in the Izu Penin——sula, Japan, J. G. G., 32, 721——737, 1980.
[8] 祁贵仲等,地磁场的空间相关性及其在地震预报中的应用,地球物理学报,20, 1, 169—— 184, 1977.
[9] Shapiro, V., et al., Anomalous Variations of the Geomagnetic Field in East Faragana——Magnetic Precursor of the Alay Earthquake with M=7.0, G. J. R. Astr. Soc., 68, 1——5, 1982
[10] Shapiro, V., et al., Some Results of the Investigation of Geomagnetic Field Variation in the Urals and Carpathians, G. J. R. Astr. Soc. 66, 1, 71——81, 1981.
[11] Johnston, M., Tectonomagnetic Effects, Earthquake Information Bulletin, 10, 3,82——87,1978.
[12] Nagata, T., Main Characteristics of Recent Geomagnetic Secular Variation,J.G.G., 17, 263——276,1965
[13] 林云芳等,中国华北地区地磁长期变化的分析,地震学报,4, 1, 74——83,1982.
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