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为提高北京遥测地震台网的地震参数测定能力,对北京地区(38°—41°N,114°—119°E)建立了一个新的地震波速度模型MDBJ81。这一模型有四个水平层置于均匀半空间之上,第一层分成三块,以反映该地区浅部结构的横向差异及地形起伏效应。在联合测定地震参数和速度结构过程中,其可调整速度模型参数包括:各层中的平均P波速度,各层层顶深度,第一层三块厚度以及平均P波S波速度比。通过分离参数,避免了求解大型方程组。 最后求解中使用了北京台网1979年记录的43个地震,共836个P波及S波震相到时。结果表明,北京周围地区的确存在速度结构的横向差异,第一层底深度自西北向东南逐块增加。得到的新震中位置一般比原台网测定位置更靠近表面断层线。
A new seismic velocity model MDBJ81 was developed for the Beijing area (38 ° -41 ° N, 114 ° -119 ° E) in order to improve the seismic parameters of Beijing telemetered seismic network. The model has four horizontal layers above the uniform half-space with the first layer divided into three sections to reflect the lateral differences in the shallow structures and the topographic relief in the area. In the joint determination of seismic parameters and velocity structure, the parameters of the adjustable velocity model include the average P-wave velocities of each layer, the depth of each layer, the thickness of the first layer and the average P-wave S-wave velocity ratio. By separating the parameters, solving large equations is avoided. In the final solution, 43 earthquakes recorded by Beijing Network in 1979 were used, a total of 836 P-wave and S-wave phases arrived. The results show that there is indeed a horizontal difference in velocity structure around Beijing, with the depth of the first floor increasing block by block from northwest to southeast. The resulting new earthquake location is generally closer to the surface fault line than the original station.