模拟倾斜界面情况下区域地震范围内的长周期Pnl波

MODELING LONG-PERIOD Pnl WAVEFORMS AT REGIONAL RANGES IN DIPPING STRUCTURE

中国大陆地壳厚度的特点是东部地区薄西部地区厚,因此在计算Pnl波的Green函数时进一步考虑了莫霍界面倾斜的影响.本文将广义射线理论推广到倾斜层结构模型,该方法的计算结果与有限差分的计算结果有很好的一致性.理论计算表明,在同一个倾斜结构模型中沿相反方向传播的Pnl波有明显的差异.因此当地壳厚度的变化不能忽略时,根据水平层模型的理论计算结果拟合Pnl波记录时效果不够理想.对菏泽、门源地震资料的处理结果表明,用一个更接近实际地壳的倾斜层模型来拟合Pnl波比用等效厚度平行层模型来拟合要更为合理.

The crustal thickness of Chinese continent is thin in east and thick in west, so we consi- dered the effects of inclination of Moho by calculating Green function of Pnl waves. In this paper the generized ray theory is extended to dipping structure, the result of this method has excellently consistence with the finit-difference, Theorifical calculation shows that the Green functions of Pnl waves traveling in opposite direction are obviously different in the same dipping structure. If the variations of crustal thickness can not be ignored, synthetic seismograms based on parallel model are not reasonable. Treating the result of Heze and Meyuan earthquake records shows that a dipping model is more suitable than a parallel model to simulate Pnl waveforms.