由多个小地震推断的华北地区构造应力场的方向
EVALUATION OF THE DIRECTION OF TECTONIC STRESS IN NORTH CHINA FROM RECORDED DATA OF A LARGE NUMBER OF SMALL EARTHQUAKES
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摘要: 利用1966——1978年间华北地区区域地震台记录的5级以下地震的初动方向,通过求平均节面解推断出13个分区的地壳构造应力场的主应力轴方向.通过数值试验论证了利用多个断层面随机取向的地震的 P、B、T 轴推断构造应力主轴方向的可能性.讨论了在推断构造应力场方向时,利用多个小地震资料比利用大地震资料所具有的优越性.用尝试法对所有可能解的三维参数空间以555的间隔进行了扫描搜索,改进了扫描方法,节省了计算时间.Abstract: Based on the first motion polarization records of earthquakes with magnitude less than 5 obtained from local Seismological stations in North China during the period of 1966 -1978, the directions of the principal axes of crustal tectonic stress in 13 subregions are inferred by computing the composite nodal plane solutions.A numerical computation test shows the possibility of inferring the principal axes of tectonic stress from the P, B, T axis of earthquakes with randomly oriented fault planes. The advantage of using microearthquake polarity data over using the data from large earthquakes in estimating the direction of tectonic stress is argued. By use of the trial and error method, the 3-dimensional parameter space of all possible average nodal plane solutions is tested with the scan step of 555, the computation time is saved by improving the program.
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[1] 李钦祖,华北地壳应力场的基本特征,地球物理学报,23, 4, 376——388, 1980.
[2] L. Zobaek and M. Zoback, State of Stress in the Conterminous United Sbatea. J. Geophys.Res., 85,B11, 6113——6156, 1980.
[3] 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.
[4] 许忠淮等,京、津、唐、张地区地震应力场的方向特征,地震学报,1, 2,121——132,1979.
[5] S. Guinn and L. T. Long, A Computer Method for Determination of Valid Pocal Mechauiama Using P——wave First Motions, Eartleq. Notes, 48, 4, 21——33, 1977.
[6] D. P. Mekenzie. The Relationship between Fault Plane Solutions for bona of the Principal Stresses, Bull. Seismol. Soc. Amer, 59 591——601,1969.
[7] N. Yamakawa, Stress Fields in Fields in Focal Regions, J. Phys. Earth, 19, 347——353,1971.
[8] A. J. Pope, Fiducial Regions for Body Wave Focal Plane. Solutions, GeoPhyhs. J. R. Astr. Soc. 30,331——342,1972.[1] 李钦祖,华北地壳应力场的基本特征,地球物理学报,23, 4, 376——388, 1980.
[2] L. Zobaek and M. Zoback, State of Stress in the Conterminous United Sbatea. J. Geophys.Res., 85,B11, 6113——6156, 1980.
[3] 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.
[4] 许忠淮等,京、津、唐、张地区地震应力场的方向特征,地震学报,1, 2,121——132,1979.
[5] S. Guinn and L. T. Long, A Computer Method for Determination of Valid Pocal Mechauiama Using P——wave First Motions, Eartleq. Notes, 48, 4, 21——33, 1977.
[6] D. P. Mekenzie. The Relationship between Fault Plane Solutions for bona of the Principal Stresses, Bull. Seismol. Soc. Amer, 59 591——601,1969.
[7] N. Yamakawa, Stress Fields in Fields in Focal Regions, J. Phys. Earth, 19, 347——353,1971.
[8] A. J. Pope, Fiducial Regions for Body Wave Focal Plane. Solutions, GeoPhyhs. J. R. Astr. Soc. 30,331——342,1972.
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