检波器与灰岩地表耦合效应的理论和试验研究

Theoretical study and tests on geophone-limestone coupling effect

检波器与灰岩地表的耦合问题是影响中国南方海相灰岩裸露区地震资料品质的重要因素之一。本文利用多自由度振动系统理论模型,分析了检波器—灰岩地表耦合系统的响应特征,并结合检波器耦合试验资料,对比了不同耦合模式的耦合效果,探讨了检波器—灰岩耦合机制。研究结果表明,将检波器尾锥插入灰岩地表构成双自由度耦合振动系统,在保证两者紧密接触时对应的耦合谐振频率较高,对地震资料品质影响很小,但施工难度较大;利用表土等耦合介质将检波器埋置在灰岩地表构成的三自由度耦合振动系统,提高了施工效率,但需选择合适的耦合介质、减小耦合介质的高度及其与灰岩的接触面积,以减小耦合谐振的影响,进而提高地震资料品质。

The geophone-limestone coupling problem is one of the important factors which influence quality of seismic data in marine carbonate outcrops area of South China.In this paper,using multi-freedom degree vibration system theoretical model,we analyze the response characters of geophone-limestone coupling system.Then combining the theoretical results with field test results,we compare seismic data collected from different geophone coupling modes and discuss the geophone-limestone coupling mechanism.The results show that it is 'two degrees of freedom coupling vibration system' to make geophone spike insert into limestone ground.And the resonance frequency is very high and coupling system's influence is very little when making geophone spike insert into limestone ground tightly.But seismic acquisition efficiency is low using this geophone coupling mode.The results also show that it is 'three degrees of freedom coupling vibration system' to bury geophone on the limestone ground using coupling mediums such as surface soil.And the seismic acquisition efficiency is high using this geophone coupling mode.However,when using the latter geophone coupling mode,we need to select proper coupling medium and reduce contact acreage between coupling medium and limestone ground and coupling medium's height in order to weaken the coupling resonance.