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
ON THE DIRECTION OF THE MAXIMUM COMPRESSIVE PRINCIPAL STRESS BEFORE AND AFTER THE 1976 SONGPAN-PINGWU EARTHQUAKE(M=7.2) OF THE SICHUAN PROVINCE
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摘要: 本文应用1966mdash;1976期间,甘肃南部和四川北部地区地震P波初动方向资料,求出平均节面解,据此推断松潘mdash;平武7.2级地震前,孕震应力场的最大主压应力方向为近东西向。但由松潘台资料所得最大主压应力轴的方向,在震前显示出近90deg;的转动。 由余震资料所得释放应力场的最大主压应力方向,亦为近东西向。Abstract: The average nodal plane solutions of the earthquakes occurred in southern Gansu and northern Sichuan Provinces from 1966 to 1976 are obtained by use of P-wave onset data. On the basis of these solutions, it can be inferred that the direction of the maximum compressive principal stress during the process of development of the earthquake is nearly east-west before the Songpan-Pingwu Earthquake. Whereas that obtained from the data of the Songpan seismological station, it appears to have been rotated by an angle of about 90? However the direction of the maximum compressive principal stress in releasing as obtained from data of aftershocks is also nearly east-west.
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[13] I. N. Gupta, Precursory reorientation of Stress aLea due to vertical migration of seismic astivity, J. G. R., S0, 2, 272——273, 1975.[1] K. AKI, Earthquake generating stress iu Japan for the years 1961 to 1963 obtained by smoothing the first motion patterns, Bull. Earthq. Res. Inst., 44, 447——471, 1966.
[2] 李钦祖等,由单台小地震资料所得两个区域的应力场,地球物理学报,16, 49——61; 1973.
[3] 许忠淮等,京、津、唐、张地区地震应力场的方向特征,地震学报,I, 2, 121——132, 1979.
[4] 112. A. Sadovaky et al., The processes preceding strong earthquakes in some region of Middle Asia, Tectouophysics, 14, 3/4, 295——307, 1972.
[5] I. G. Simbireva, Focal Mechanism of Weak earthquakes in the Naryn River Basin, in: M. A. Sadovaky (Editor), experimental seismology, Science Press, Moscov", 1973, 423 pp. Translated in English from Russiaai by D. B. Vitaliano, U. S. Geological Survey.
[6] 成尔林,四川及其邻区现代构造应力场和现代构造运动特征,地震学报,3, 3, 231, 1981.
[7] V. I. Keylis——Borok and L. N. Malinovskaya, One regularity in the occurrence of strong earthquakes, J. G. R., 69, 14, 3019——3024, 1964.
[8] M. Wysa, Precursors to the Garm earthquake of March 1969, J. G. R., 80, 20, 2926——2930.1975.
[9] 112. Bath and S. J. Duds, Earthquake Volume, fault plane area, Seismic energy, Strain, Deformation, and related quantities, dnn. Geophys (Rome), 17, 353——368, 1964.
[10] 傅承义、陈运泰、陈颗,我国的震源物理研究,地球物理学报,22, 4, 315——320, 1979.
[11] N .Yamakawa, Stress fields in focal regions, J. Phys. Earth, 19, 347——355, 1971.
[12] B. T. BRADY, Theory of earthquake, II, inclusion theory of crustal earthquake, Pure and Appl, Geophys, 113, 149——168, 1975.
[13] I. N. Gupta, Precursory reorientation of Stress aLea due to vertical migration of seismic astivity, J. G. R., S0, 2, 272——273, 1975.
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