新丰江水库地震区内孔隙流体扩散与原地水力扩散率的研究.

本文根据新丰江水库地震的主要成因是水渗透的结果,采用了地震活动的震中分布面积扩散法,利用新丰江水库蓄水以后 MS2.0的地震资料,研究了主震区的水力扩散率.研究结果表明,在新丰江水库地震活动中的前震活动中,原地水力扩散率基本上稳定在6.2m2/S,而主震发生以后震源区的原地水力扩散率增大约50％,即为9.7m2/S.在主震发生后的较长时间里.原地水力扩散率出现了明显的各向异性及受水位涨落等因素的影响,没有一定的规律可循.本文还用室内岩石渗透实验的结果与原地水力扩散率估计值进行了比较,说明室内含破裂面岩样的渗透率同原地渗透率吻合得较好,而完整岩样的渗透率要比原地渗透率低3个数量级.最后将本文地震活动的震中分布面积扩散法的局限性进行了讨论.

RESEARCH ON THE DIFFUSION OF PORE FLUID AND IN-SITU HYDRAULIC DIFFUSIVITY IN THE EPICENTRAL REGION OF XINFENGJIANG RESERVOIR EARTHQUAKES

According to the fact that the Xinfengjiang reservoir earthquakes are caused mainly by water seepage, this paper, using the data of Ms2.0 earthquakes, studies the hydraulic diffusivity of the main- shock zone by the expansion of the distribution area of epicenters. It is indicated that in- situ hydraulic diffusivity during the preshock activity of the Xinfengjiang reservoir region was about 6.2m2/s. However, after the main shock, the in - situ hydraulic difiusivity in the main shock region increased by fifty percent, that is to say, to 9.7m2/s. During the long period after main shock occurrence the in - situ hydraulic difiusivity was affected by significant anisotropy of the medium and fluctuation of water level. No regularity can be found. In addition, we compare the difiusivity found by experiment with rock samples collected with the in - situ hydraulic difiusivity estimated. It is shown that the difiusivity of rock samples with fractures is about the same as the difiusivity estimated in- situ. However, the difiusivity of whole rock samples is 3 orders of magnitutes smaller than that estimated in - situ. Finally, we discuss the limits on the method by the expansion of distribution area of epicenters in the study of reservoir induced seismicity.