量规函数、台站方位、台基及不同测量方法对近震震级 MLsub> 的影响
THE EFFECTS OF THE CALIBRATION FUNCTION,AZIMUTHS AND SITES OF THE STATIONS AND DIFFERENT METHODS OF APPROACH ON THE MAGNITUDE DETERMINATION OF NEAR EARTHQUAKES, ML
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摘要: 本文研究了量规函数、台站方位、台基以及不同测量方法对测定震级 ML 的影响.结果表明:1)得到了一个新的量规函数 R3（△）,它比原有的 R1（△）和 R2（△）更适合于我国西南地区:2)由于地震波辐射的方向性,处在不同方位的台站震级差可达0.3——0.5级.用 P 波与S 波的某种组合可消除一些方向性影响;3)基岩台基的校正值不大.某些较大的台基校正值可能是仪器放大倍数没测准的影响;4)除用 S 波的水平分量求震级外,S 波的垂直分量以及 P 波的水平分量和垂直分量乘以适当的倍数后,都可用来求震级 ML.求得的结果与常规方法的结果之间几乎没有什么差别.Abstract: The effects of the calibration function, the azimuthal angles of the stations relative to the earthquakes, the ground conditions of the station sites and also the different methods of approach on the magnitude determinations of near earthquakes ML have been studied. The results are as follows:(1) A new calibration function R3(△) can be found for southwestern China better than the original ones R1(△) and R2(△).(2). Due to the azimuthal variation of wave radiation, magnitude determinations at stations located in different azimuths differ by about 0.3-0.5 in ML. Proper combination of P and S waves can reduce to certain extent the azimuthal effect.(3) Corrections for the station sites on bed rocks are relatively small. However, some larger correction values may be attributed to erroneous magnification values of the seismographs.(4) Besides using horizontal components of the S-wave, the vertical component of S-wave and the horizontal and vertical components of the P-wave, multiplied by appropriate factors may also be used for determining the local magnitude ML, giving nearly the same values as the ordinary method.
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[3] 中国科学院地球物理所编著,近震分析,地震出版社,1977
[4] L. Christoskov, N. Y. Kondonskaya and J. Vanek, Homogeneous magnitude system of the Eurasian continent, Tectonophysics, 49, 131——138, 1918.
[5] P. L. Willmore, Manual of seismological observatory practice, 1919.
[6] K. Tsumura, Determination of earthquake magnitude from total duration of oscillation, Bull Earth. Res. Inst., Tokyo, 45, 7——18, 1967.
[7] W. H. K. Lee, etc., A method of estimating magnitude of local earthquake from signal duration, U.S. Geological Survey open file report, 1972.
[8] W. H. A. Lee and R. J. Wetmiller, Survey of practice in determining magnitude of near earthquakes, OVorld Data Center A for Solid Earth Geophysics, Report Se——9,1978.[1] 陈培善等,从断裂力学观点研究地震的破裂过程和地震预报,地球物理学报,20,3,1977.
[2] 陈培善等,唐山地震前后京津唐张地区的应力场,地球物理学报,21,1,1978,
[3] 中国科学院地球物理所编著,近震分析,地震出版社,1977
[4] L. Christoskov, N. Y. Kondonskaya and J. Vanek, Homogeneous magnitude system of the Eurasian continent, Tectonophysics, 49, 131——138, 1918.
[5] P. L. Willmore, Manual of seismological observatory practice, 1919.
[6] K. Tsumura, Determination of earthquake magnitude from total duration of oscillation, Bull Earth. Res. Inst., Tokyo, 45, 7——18, 1967.
[7] W. H. K. Lee, etc., A method of estimating magnitude of local earthquake from signal duration, U.S. Geological Survey open file report, 1972.
[8] W. H. A. Lee and R. J. Wetmiller, Survey of practice in determining magnitude of near earthquakes, OVorld Data Center A for Solid Earth Geophysics, Report Se——9,1978.
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