高分辨率地震数据采集系统中的低切滤波器

Low-cut Filters in High Resolution Seismic Data Acquisition System

在高分辨率地震数据采集系统中 ,设置具有较高截止频率的低切滤波器 ,它在信号通放频带范围内 ,通过对低频的衰减达到相对提升高频的目的。本文建立了低切滤波器截止频率 f0 、阶次 n与地层波速 V、可分辨地层最小厚度Δ h及地层吸收衰减系数 A的关系。要想识别更薄的地层 ,就要求低切滤波器具有大的截止频率和高的阶次 ,这会带来降低频带宽度的后果 ,给识别薄层带来困难。通过设置低切滤波器提高分辨率 ,是以牺牲地震信号的能量、降低信噪比为代价的 ,使得中、深层勘探识别 5

Low cut filters (LCF) with relatively high cut off frequency used in high resolution seismic data acquisition system give rise to the high frequency signal by attenuating its low frequency portion in its passing band. This paper has set up a relation among cut off frequency f 0,order n of LCF and wave velocity V,the minimum resolvable thickness Δh, and the absorption and attenuation factor A of Earth's strata. The thinner the resolvable layer needed, the higher the cut off frequency and order of LCF are required, and this will result in narrowing the passing band make it difficult for recognition of thin layer. The LCF used for improving resolution has traded off the energy and signal to noise ratio of seismic signal, thus makes it impossible to resolve less than 5 meters thick strata in mid and deep layer prospecting.