潮汐应力对地震的触发作用
SEISMIC TRIGGERING EFFECT OF TIDAL STRESS
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摘要: 文中计算了由日、月引潮力在地球内产生的潮汐应力场,研究了潮汐应力对地震的触发作用.采用的地球模型是分为十五层的球对称模型.对于近30年来我国或我国邻近发生的七十次较大的地震,计算了震源处在发震时刻的球坐标系中的潮汐应力.通过坐标变换,得到了发震断层面中的正应力及沿错动矢量方向的剪应力.根据岩石的库仑剪破裂准则来判断潮汐应力对所研究的震例是否具有触发作用.结果表明,在七十个震例中,潮汐应力对其中四十三个有触发作用.对于华北地区的十八个震例,潮汐应力对其中十四个有触发作用.还可看出,对于浅源走滑型地震有较明显的触发作用,而对浅源斜滑及倾滑型地震则没有明显的触发作用.对国外七十二个震例的计算结果得到了类似的结论.最后,对华北地区中任一可能的发震地点,提出一种根据潮汐应力来预测发震的危险时间范围的方法.Abstract: The tidal stress field of a layered spherically symmetric Earth due to the Sun and Moon is used to investigate its relation with earthquake occurrence. For the 70 strong earthquakes occurred during the last 24 years in or near China, we computed the tidal stress in spherical polar co-ordinate at the focus at the time of occurrence. The normal and tangential stress components along the slip direction on the earthquake fault plane are then found by co-ordinate transformation. Coulomb's criterion of shear fracture is used to determine whether these stress components will trigger the earthquakes or not.The results show that among the 70 earthquakes, 43 have had triggering effect and for the 18 events occured in North China 14 of them have had triggering effect. It may be concluded that for shallow strike slip earthquakes there are significant triggering effect, while for oblique slip and dip slip earthquakes tidal stress has very little triggering effect. From 72 events occurred over other parts of the world similar conclusion is obtained.Finally, for the purpose, of earthquake prediction, a way in finding a time interval during which the tidal stress may trigger earthquake on possible faults in North China is suggested.
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[1] L. Knopoff, Earth tides as a triggering mechanism for earthquakes, Bull. Seism. Soc. Am., 54, 1865——1870, 1964.
[2] C. H. Dix, Triggering of some earthquakes, Proc. Japan .4cad., XL, 6, 410——415, 1964.
[3] A. Ryall, J. D. Van Wonner, and A. E. Jones, Triggering. of microearthquakes by Earth tides, and other features of the Truckee, California, earthquake sequence of September, 1966, Bull. Seism. Soc. Am., 58, 215——248, 1968.
[4] J. F. Simpson, Earth tides as a triggering mechanism for earthquakes, Earth and Planetary Science Leuers, 2, 473——478, 1967.
[5] T. H. Heaton, Tidal triggering of earthquakes, <:eophys.].R, astr. Sot., 43, 307——326, 1975.
[6] 杜品仁,潮汐与地震关系初探,地震科学研究,1, 14——20, 1981.
[7] 高锡铭,殷志山,王威中,黄利娟,李健,固体潮应力张量对地震的触发作用,地壳形变与地震,创刊号,4——16,1981.
[8] H. Takeuchi, On the Earth tide in the compressible earth of varying density and elasticity, J. Fae. Sci., University of Tokyo, Sect. II 7, part 11, 1——153, 1951
[9] 王仁,丁中一,轴对称情况下地球自转速率变化及引潮力引起的全球应力场,天文地球动力学文集,上海天文台1979年编辑出版,8——21, 1978.
[10] 王仁、丁中一、殷有泉,固体力学基础,地质出版社,第71200页,1979.
[11] J. C. Jaeger .and N. G. W., Cook, Fundamentals of Rock Mechanics, 3rd. ed., p. 379, 1977.[1] L. Knopoff, Earth tides as a triggering mechanism for earthquakes, Bull. Seism. Soc. Am., 54, 1865——1870, 1964.
[2] C. H. Dix, Triggering of some earthquakes, Proc. Japan .4cad., XL, 6, 410——415, 1964.
[3] A. Ryall, J. D. Van Wonner, and A. E. Jones, Triggering. of microearthquakes by Earth tides, and other features of the Truckee, California, earthquake sequence of September, 1966, Bull. Seism. Soc. Am., 58, 215——248, 1968.
[4] J. F. Simpson, Earth tides as a triggering mechanism for earthquakes, Earth and Planetary Science Leuers, 2, 473——478, 1967.
[5] T. H. Heaton, Tidal triggering of earthquakes, <:eophys.].R, astr. Sot., 43, 307——326, 1975.
[6] 杜品仁,潮汐与地震关系初探,地震科学研究,1, 14——20, 1981.
[7] 高锡铭,殷志山,王威中,黄利娟,李健,固体潮应力张量对地震的触发作用,地壳形变与地震,创刊号,4——16,1981.
[8] H. Takeuchi, On the Earth tide in the compressible earth of varying density and elasticity, J. Fae. Sci., University of Tokyo, Sect. II 7, part 11, 1——153, 1951
[9] 王仁,丁中一,轴对称情况下地球自转速率变化及引潮力引起的全球应力场,天文地球动力学文集,上海天文台1979年编辑出版,8——21, 1978.
[10] 王仁、丁中一、殷有泉,固体力学基础,地质出版社,第71200页,1979.
[11] J. C. Jaeger .and N. G. W., Cook, Fundamentals of Rock Mechanics, 3rd. ed., p. 379, 1977.
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