深井中地震波观测结果的某些物理解释

随着深井观测地震台网的进一步发展,在深井中获得的地震资料反映出了不少有意义的信息。本文对纵向不同深度上记录的地震波特征进行了分析和研究,探讨了纵向不同深度上各点之间记录的地震波走时差异和振幅差异的物理成因,指出了台基介质特性及空间状态(全空间或半空间)对地震波传播特征和记录特征的影响,并用软盖层效应加以统一解释。结果表明,在地下纵向不同深度上,自下而上直至地面,地震波的位移幅度逐渐放大、走时加长、周期变大;平原地区的松散沉积覆盖层对地震波产生放大、延时和滤波作用;在井下可以观测到向下传播的地面反射波,因而使得波列变复杂。

SOME PHYSICAL EXPLANATION FOR THE DATA OF SEISMIC WAVES OBSERVED IN DEEP HOLES

With the development of the deep-hole seismic network,much significant information has been reflected in the seismic data observed in deep holes.In this paper,the characteristics of seismic waves recorded at different longitudinal depths are analysed and studied;the physical origins for the travel-time difference of seismic waves and the amplitude difference recorded at various longitudinal depths are investigated;the effects of the characteristics for the medium of the station base and its spacial condition (full space or semi-space) on the characteristies of propagation and record of seismic waves are indicated;and then all above-mentioned is explained uniformly by the theory of softcovering effect.The results show that at different longitudinal depths under the earth,ranging from bottom to top until the earth surface,the displacement amplitude of seismic waves is amplified gradually,the travel time lengthened and the period enlarged.The loose deposit overburden in the plain area has the effect of amplification,delay and filter on the seismic waves.The reflection wave propagated downwards from surface can be observed in the holes,therefore,the wave column becomes more complicated.