小震震源机制P轴取向的预报应用
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摘要
采用Snoke的振幅比方法,利用江苏台网和山东台网记录到的数字化波形资料,计算了发生在江苏及其附近地区的33个地震的震源机制解,并由此计算了其相应的P轴取向。结果表明:南黄海北部凹陷地区M_L5.1地震发生前2个月内、长江口地区显著小震群发生之前2个月内,在震中所在区域的附近地区有震源P轴取向小于100°的异常地震发生;盐城附近及其近海海域在本文研究的时段内未曾出现震源P轴取向小于100°的地震,该区域也没有发生中强地震或显著小震群事件。由此说明震源P轴取向具有一定的短临前兆意义,但这种情况与大地震事件所表现出来的规律并不完全相同。茅山断裂附近地区出现的2次震源P轴取向小于100°的事件与该地区重力异常结果是一致的,说明2002年前后茅山断裂曾活动过。
In this paper the source mechanisms of 33 earthquakes and the P axis-trends are obtained whichoccurred in JiangSu and its neighborhood, by using the Snoke's method of swing ratio and the digital wavedata recorded by JiangSu net and SanDong net. The result indicates that some abnormal earthquakeswhose P axis-trends are smaller than 100° occurred in about two months before ML5.1 earthquake in thenorthern Sunken region of the Yellow Sea or remarkable event occurs in the Yangtse River intake region;and no abnormal earthquakes occur whose P axis-trends are smaller than 100° and also remarkable eventsor moderate earthquakes occur in the YanCheng neighborhood and its adjacent sea area. These obviouslydemonstrate that the P axis-trend of source may be useful for the short-term and imminent prediction.which, however, is not in agreement with the phenomenon of great seismic events. The phenomenon ofthe two events with P axis-trends smaller than 100° agrees well with that of the abnormal gravity withinthe MaoSan fault area, which shows that the MaoSan fault were active around the year of 2002.
In this paper the source mechanisms of 33 earthquakes and the P axis-trends are obtained whichoccurred in JiangSu and its neighborhood, by using the Snoke's method of swing ratio and the digital wavedata recorded by JiangSu net and SanDong net. The result indicates that some abnormal earthquakeswhose P axis-trends are smaller than 100° occurred in about two months before ML5.1 earthquake in thenorthern Sunken region of the Yellow Sea or remarkable event occurs in the Yangtse River intake region;and no abnormal earthquakes occur whose P axis-trends are smaller than 100° and also remarkable eventsor moderate earthquakes occur in the YanCheng neighborhood and its adjacent sea area. These obviouslydemonstrate that the P axis-trend of source may be useful for the short-term and imminent prediction.which, however, is not in agreement with the phenomenon of great seismic events. The phenomenon ofthe two events with P axis-trends smaller than 100° agrees well with that of the abnormal gravity withinthe MaoSan fault area, which shows that the MaoSan fault were active around the year of 2002.
引文
① 江苏省地震局,江苏省年度地震趋势研究报告.2003
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[2] Snoke J. A. Earthquake Mechanisms[A]. Encyclopedia of Geophysics (D. E. James, Ed.)[C]. Van Nostrand Reinhold Company, New York, 1989． 239-245
[3] Snoke J. A. Clyde and the Gopher: a preliminary analysis of the 12 May Sakhalin Island event [J]. Seism. Res. Letters, 1990, 61: 161
[4] 刘杰,郑斯华,康英,等.利用P波和S波的初动和振幅比计算中小地震的震源机制解[J].地震,2004,24(1) ;19-26
[5] Sadovsky M A. The processes preceding strong earthquakes in some regions of Middle Asian[J]. Tectonophysics, 1972, 14(3/4) : 116-125
[6] Sadovsky M A, Nersesov I L. Ferecasts of earthquakes on the basis of complex geophysical features [J]. Tectonophysics, 1974, 23 (3) : 135-142
[7] 许忠淮,刘玉芳,张郢珍.京津唐张地区地震应力场的方向特征[J].地震学报,1979,1(2) :13-18
[8] 华祥文.唐山强震前后北京、天津周围地区应力场的变化过程[J].地震学报,1980,2(2) :33-37
[9] 成尔林,李桂芳,陈和川,等.1976年四川省松潘-平武7． 2级地震前后主压应力轴的方向特征[J].地震学报,1982,4(2) :15-19
[10] 阚荣举,刘祖荫,王绍晋,等.龙陵地区大震前后平均应力轴取向的时间变化[J].地球物理学报,1983,26(6) :38-41
[11] 孙加林.关于强震前后中小地震平均主压应力方向和初动符号矛盾比变化问题的研究[A].国家地震局科技监测司编.地震预报方法实用化研究文集(地震学专辑)[C].北京:地震出版社,1989． 55-57
[12] 王炜.霍山震群前后的波速异常及小震活动特征[J].地震科学研究,1980,第一辑:81-85
[13] Brady B T.地震理论(一):与尺度无关的岩石破坏理论,地震理论(二);地壳地震包体理论[A],地震理论与实验译文集[C].北京:地震出版社,1979． 70-89
[1] Snoke J. A., Munsey J. W., Teague A. C., et al. A program for focal mechanism determination by combined use of polarity and SV-P amplitude ratio data [J]. Earthquake Notes, 1984, 55 (3) : 121-128
[2] Snoke J. A. Earthquake Mechanisms[A]. Encyclopedia of Geophysics (D. E. James, Ed.)[C]. Van Nostrand Reinhold Company, New York, 1989． 239-245
[3] Snoke J. A. Clyde and the Gopher: a preliminary analysis of the 12 May Sakhalin Island event [J]. Seism. Res. Letters, 1990, 61: 161
[4] 刘杰,郑斯华,康英,等.利用P波和S波的初动和振幅比计算中小地震的震源机制解[J].地震,2004,24(1) ;19-26
[5] Sadovsky M A. The processes preceding strong earthquakes in some regions of Middle Asian[J]. Tectonophysics, 1972, 14(3/4) : 116-125
[6] Sadovsky M A, Nersesov I L. Ferecasts of earthquakes on the basis of complex geophysical features [J]. Tectonophysics, 1974, 23 (3) : 135-142
[7] 许忠淮,刘玉芳,张郢珍.京津唐张地区地震应力场的方向特征[J].地震学报,1979,1(2) :13-18
[8] 华祥文.唐山强震前后北京、天津周围地区应力场的变化过程[J].地震学报,1980,2(2) :33-37
[9] 成尔林,李桂芳,陈和川,等.1976年四川省松潘-平武7． 2级地震前后主压应力轴的方向特征[J].地震学报,1982,4(2) :15-19
[10] 阚荣举,刘祖荫,王绍晋,等.龙陵地区大震前后平均应力轴取向的时间变化[J].地球物理学报,1983,26(6) :38-41
[11] 孙加林.关于强震前后中小地震平均主压应力方向和初动符号矛盾比变化问题的研究[A].国家地震局科技监测司编.地震预报方法实用化研究文集(地震学专辑)[C].北京:地震出版社,1989． 55-57
[12] 王炜.霍山震群前后的波速异常及小震活动特征[J].地震科学研究,1980,第一辑:81-85
[13] Brady B T.地震理论(一):与尺度无关的岩石破坏理论,地震理论(二);地壳地震包体理论[A],地震理论与实验译文集[C].北京:地震出版社,1979． 70-89
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