澜沧—耿马地震的S波偏振

S-WAVE POLARIZATION OF LANCANG-GENGMA EARTHQUAKE

通过对1988年11月6日澜沧—耿马7.6、7.2级强震前后S波偏振角的计算分析,得出大震前偏振角变化幅度小,U_(SH)—U(SV)值图象呈规则分布;大震后到11月30日6.7级强余震前,偏振角变化幅度增大,U_(SH)—U_(SV)值图象散开,分布方向仍与前震相似。6.7级强余震发生后,偏振角变化幅度大,U_(SH)—U_(SV)值图象弥散分布,线性和方向性消失。与此同时,对前震、余震的P波S波最大振幅比值变化分布进行研究,得出大震前小震破裂面方向是北北西向,与主震破裂面相同,余震的破裂面与主震破裂面不完全相同,是主断面激发多组不同方向的新断面参与活动。

Through calculation and analysis of S-wavc polarization angles before and after the Nov. 6, 1988, Lancang-Gengma earthquake ( M = 7.6, 7.2 ), the following results have been obtained that, the amplitude variations [of polarization angles were small before the great event, with a regular distribution of USH-UfiF pattern; and the variations increased from the great event till the Nov. 30 M6.7 strongest aftershock, with a spread USH-USV pattern but a similar distributive direction to that before the event. After the M6.7 strongest aftershock, the amplitude variations of polarization angles were large, with scattered distribution of USH-USV pattern but the linearity and direction disap-p?arcd. At the same time, distributions of the maximum P and S wave ampliltid rato of fore (?)