井下与地面地震波记录特征的对比研究

本文对比研究了平原地区井下和地面的地震波记录特征,对其走时关系和振幅关系进行了推导,得出: 1.在层状均匀介质条件下,在地面记录到的地震波走时tc大于在井下记录到的地震波走时th,二者之差为 △t=tc——th=cosic/Vch与此相应,地面震相观测到时Tc滞后于井下震相观测到时Th,其到时差为△T。 2.定义地面振幅Ac与井下振幅Ah之比为 K=Ac/Ah在特定的条件下,K>1。因而称K为地面振幅相对于井下振幅的放大因子。 分析了静海地震台井下和地面的地震观测资料,得到单台的△T和K的对比结果,并将其记录特征分别与基岩地震台的记录特征进行了比较,认为: 1.对于运动学参数,井下较之地面,更逼近于基岩地区的情况。 2.对于动力学参数,统计得出基岩地震台的地动振幅A与Ah,Ac的关系: A=3.50Ah A=0.34Ac。

COMPARATIVE STUDY BETWEEN THE CHARACTERISTICS OF SEISMIC WAVES RECORDED DOWNHOLE AND ON GROUNDSURFACE

A comparative study between the characteristics of seismic waves recorded downhole and on groundsurface in plain area is made; the travel time and the amplitude relationships of which are derived in this paper. Then the following conclusions are drown:1. Under the condition of uniform layered medium, tc, the travel time of seismic waves recorded on the ground is larger than th, the value recorded downhole. Their difference is given as follow:△t=tc-th=cosic/Vch Correspondingly, Tc, the travel time of seismic phase observed on groundsurface is greater than Th, the value observed downhole. The difference is represented by △T.2. Ahe ratio of Ac, the groundsurface amplitude to Ah, the downhole amplitude is defined as K = Ac/AhUnder specified conditions, K>1. Thus K is considered as the amplifying factor of the groundsurface amplitude relative to the downhole amplitude.The data observed downhole and on groundsurface at the Jinghai station are analysed and the results from the comparison between △T and K at a single station are obtained.