基于Lg波识别判据的特性分析

Analysis on discriminants based on Lg wave

Lg波是检测、识别地下核爆炸的重要震相.通常情况下,地下核爆炸的低频段Lg波能量相对较强,基于Lg波的识别判据在高频段表现较好.然而在低频范围内却表现出难以用球对称爆炸源模式解释的现象,如Lg/Pg判据在1Hz附近失效等现象.本文利用理论地震图方法,分析了伴随层裂过程产生的重要辅助源——CLVD源对Lg波低频成分的调制作用,给出了基于Lg波的识别判据成功及失效的原因,并将层裂过程视为输入扰动,利用振型叠加原理,进一步解释了基于Lg波识别判据特性的物理机制.这对于更好地利用Lg波识别地下核爆炸,具有较好的参考意义.

Lg wave characteristic is widely used to discriminate underground nuclear explosions from earthquakes.In contrast,the high-frequency Lg/Pg discriminant appears to perform very well,but fails around 1 Hz.This phenomenon can not be explained by pure explosion source model,but the CLVD source appears to take a key role to explain it.In this paper,the effect of CLVD source on the performance of the discriminants based on Lg wave is studied by means of theoretical seismogram analysis.Considering the spall as an input of disturbance with special frequency,we proposed a physical mechanism of the performance of Lg/Pg based on the normal mode method.An understanding of the effect on Lg caused by CLVD source can be useful not only for improving the performance of existing regional discriminants,but also for exploring new discriminants.