Seismic acceleration signal analysis and application

地震加速度信号分析与应用

Although various types of geophones are applied in seismic exploration,there are only three common types of signals produced by geophones:displacement,velocity,and acceleration signals.Currently,our understanding of the signal characteristics,such as the generation mechanism,the geophysical properties,and the significance of the corresponding rock physics,remains unclear,which makes it difficult to both scientifically evaluate and take full advantage of the different types of geophones.In this paper,the mechanism by which seismic waves are generated is studied based on the spring–damped vibration theory.The physical characteristics of the three above-mentioned signal types and the relationships among the physical properties of the signals and medium are analyzed,as well as the signalto-noise ratio(SNR),resolution,and spectrum characteristics.Based on laboratory tests,field experiments,and applications,we obtained the following conclusions.The acceleration signal reflects the elastic characteristics of the medium and the change rules,and the signal strength is positively correlated with physical property changes.The acceleration signal has favorable attributes,such as small distortion,high fidelity,strong high-frequency amplitudes,and a wide frequency band.Therefore,the acceleration signal is more suitable for high-precision seismic exploration of complex media.In addition,the P-wave acceleration signal more accurately reflects the elastic Young modulus,shear modulus,and density changes than the velocity signal.However,the sensitivity decreases with increasing shear modulus and density.For the S-wave,the acceleration signal is more sensitive to the shear modulus and density than the velocity signal.

在地震勘探中使用的检波器类型较多,但其感应振动产生的信号类型通常只有三种:位移、速度和加速度信号。对这三种信号产生的机理、物性特征、岩石物理意义等认识与理解皆不够透彻,因而难以对不同类型检波器做出客观的科学评价,影响了检波器各自优势的充分发挥,本文从弹簧阻尼振动理论入手研究了地震信号产生的机理,分析了地震信号的物理特征、信号与介质的物性关系以及它们的信噪比、分辨率和频谱等特征。实验室测试、野外试验与应用表明:加速度信号反映了介质的弹性特征和物性变化规律,信号强度与物性变化呈正相关,而且加速度信号具有畸变小,保真度高,高频强,频带宽的良好属性,因而,对于复杂介质的高精度地震勘探更适宜利用加速度信号。此外,根据加速度信号与物性参数关系,纵波加速度信号反映杨氏弹性模量、剪切模量和密度变化的灵敏度比一般速度信号要高,但随着密度和剪切模量值的增大灵敏度降低;对于横波来说,加速度信号反映剪切模量和密度变化的灵敏度也比一般速度信号高。