可控震源非线性扫描地震响应的数值模拟

Numerical simulation for seismic response to nonlinear sweeping signal from a vibrator

讨论了几种非线性扫描信号自相关函数的旁瓣特性.对可控震源非线性扫描的地震响应进行了数值模拟.当震源扫描持续时间是检波器接收时间的一半时,相关运算把反射扫描信号压缩成脉冲信号的效果是显著的.有限度地增加震源扫描持续时间以及与之相适应的接收时间可以使反射扫描信号得到进一步的压缩,但在固定扫描与接收时间的条件下,增加采样点个数对反射扫描信号的压缩并不起作用.采用具有低频相关子波特性的非线性扫描震源信号,将有利于相关噪声的消除.模拟结果还证实了二次扫描在某些特定条件下会出现鞍点效应这样一个事实.

We discuss the properties of the side lobes of autocorrelation functions for several nonlinear sweeping signals and perform the numerical simulation for seismic response to the nonlinear sweeping signal produced by a vibrator. On condition that the sweeping duration is round about half the receiving time of geophones, the effect of compressing reflective sweep signals into pulse signals with the correlation operation is very remarkable. Increasing sweeping duration and receiving duration within limits, reflective sweep signals can be further compressed. But increasing samples with invariable sweeping duration and receiving duration is not helpful to compress those. Employing the nonlinear sweep signals with the properties of low frequency correlation wavelet will be benefit to the elimination of the correlation noises. The simulation results also show that a saddle point effect will appear for the quadratic sweeping at some special conditions.