CAJ | 학술논문

本文在各向同性介质假设下,计算了薄层顶、底反射P波和PS波的理论地震图.理论模拟发现薄层的反射P波与PS波是一复合波,包括层内的多次透射和反射转换波型,且具有类似单一界面反射的、脉冲式的波形特征.两类薄层反射整体振幅随着薄层厚度的降低而缩小;在地震子波主频40 Hz条件下,2 m左右厚度的薄层反射相比单一界面反射具有等同的振幅水平.1 m以下极薄层仅有弱反射甚至无反射;薄层反射复合波振幅与炮检距的关系依然成立,但不惟一;单界面反射AVO原理、方法不适用于薄层反射解释与反演.
본문재각향동성개질가설하,계산료박층정、저반사P파화PS파적이론지진도.이론모의발현박층적반사P파여PS파시일복합파,포괄층내적다차투사화반사전환파형,차구유유사단일계면반사적、맥충식적파형특정.량류박층반사정체진폭수착박층후도적강저이축소;재지진자파주빈40 Hz조건하,2 m좌우후도적박층반사상비단일계면반사구유등동적진폭수평.1 m이하겁박층부유약반사심지무반사;박층반사복합파진폭여포검거적관계의연성립,단불유일;단계면반사AVO원리、방법불괄용우박층반사해석여반연.
In this paper the synthetic seismograms of P-and PS-wave reflections from the top and bottom of a thin layer are calculated in case of isotropic media. The results show that both P-and PS-wave reflections are composite waves resulted from different types of conversion as transmitted and reflected on two interfaces of the thin layer, and have the pulse wave form similar to reflections from single interface. The amplitudes of two kinds of reflections decrease as layer getting thinner, but are on the same level as that of single interface reflection, even if the thin layer decreases to 2 m thick when the dominant frequency is 40 Hz. The reflections from extremely thin layer below 1 m thickness are weak and even disappear. There is a relationship between composite amplitudes of thin layer reflections and offset, however, which is not unique. The theory and method for single interface reflection, about the amplitude versus offset (AVO) is not suitable to interpret and invert for thin layer parameters.