【摘要】 本文基于波动理论,利用深度域相移法对不同互层数、不同单层厚度的等厚薄互层进行正演模拟.采用广义S变换分析零偏移距地震道反射复合波的瞬时频谱.研究发现当单层厚度大于3/16波长时,等厚薄互层时域特征为中、高频等幅振荡,瞬时频谱为与单层厚度成反比的单一峰值梳状函数;当单层厚度小于3/16波长时,震源子波的有限带宽对瞬时频谱的高频频率峰有压制作用,导致等厚薄互层中部的时域振幅和频域最大幅度均为低值,薄互层的结构特征不易分辨,说明宽高频的震源子波是提高薄互层分辨能力的关键.此外,理论推导和实验分析均证明:当地层厚度大于1/8波长时,其峰值频率与薄互层单层厚度存在定量解析关系,这为等厚薄互层单层厚度定量预测提供了重要的技术手段.更多还原

【Abstract】 The isopachous thin interbeddings with different single layer thicknesses and different layer numbers are modeled by phase-shift method based on wave theory.The time-frequency responses of reflection composite wavelet from zero-offset trace are analyzed by generalized S transform.The time domain responses of isopachous thin interbedding are a kind of medium-high frequency equal amplitude oscillation when the single layer thickness is more than 3/16 wavelength.The instantaneous frequency spectrum is a Dirac comb function with single frequency peak that has an inverse relation to the single layer thickness.The single high frequency peak of instantaneous frequency spectrum is suppressed by the source wavelet spectrum which has a limited frequency band width when the layer thickness is less than 3/16 wavelength.Therefore the time domain amplitude and maximum amplitude in frequency spectrum are extremely low so that the structural features of isopachous thin interbedding can not be discriminated easily.Thus,wide-band high frequency source wavelet is the key to improve the resolving power of thin interbedding.Furthermore,the theoretical derivation and experimental analysis show that the main peak frequency has a quantitative analytical relation with the single layer thickness of reflection composite wavelet when the single layer thickness is more than 1/8 wavelength.So it can give a technological mean for predicting single layer thickness quantitatively.更多还原