基于Ganley理论含有衰减特性零偏VSP正演研究及修正  

Research and modification of VSP attenuation characteristics based on Ganley's forward theory

作　　者：武银婷[1] 朱光明[2] 刘伊克[1] 常旭[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]长安大学,西安710054

出　　处：《地球物理学报》2011年第9期2368-2374,共7页Chinese Journal of Geophysics

基　　金：国家重点基础研究发展计划(2009CB219404)资助

摘　　要：含有衰减的VSP资料能够提供丰富的地下岩层和岩性信息,本文根据Ganley理论对其进行了正演计算.引入品质因子Q值,考虑界面发生反射和透射,对震源位于地表及地下某一深度进行讨论,分别计算水平层状介质中的下行波和上行波.与不含有衰减特性的正演记录及其时频分析对比可以看出,高频成分的吸收、主频的降低、较多的能量衰减揭示了地层的非弹性性质.另外,当震源位于第一层介质以下时,按照Ganley理论公式计算得到的震源上方地层的下行波同相轴比直达波先出现,产生向上时移的现象,这表明了其波场运算存在提前到达的误差.为此,对震源上方传输系数矩阵进行修正,下行波在直达波到达后,才从分界面的位置开始出现,符合传播规律,正演结果显示了修正的合理性.VSP data can provide abundant information of seismic wave attenuation characteristics. This paper carries out forward calculations of zero-offset VSP synthetic record with attenuation. Considering reflection and refraction, the synthetic seismograms of layered attenuation models are generated based on Ganleyrs theory, which is fit for normal incident. Compared with the records without attenuation, the decrease of energy and frequency display the unelastic characteristics. We calculated the down-going and up-going wavefield with source location on the surface and underground. Unfortunately, the forward results showed that the arrival time shifted up in the down-going wavefield when the source was underground, which indicates problems in the original formula. We modify the transmission matrix and gain a corrected record, which corresponds with regular pattern.

关 键 词：零偏VSP 衰减 正演 时移 传输系数矩阵 

分 类 号：P631[天文地球—地质矿产勘探]