多波多分量波场的地震物理模型观测

The observation of multiwave multicomponent wave field with seismic physical modeling

（中国石油大学 CNPC物探重点实验室，北京 100083）

CNPC Key Lab in Geophysics, China University of Petroleum, Beijing 100083, China

在纵波震源激发的三分量记录中，经常在SH分量上得到P波或SV波的反射，通常认为这是地下不均匀或各向异性引起的，然而，均匀各向同性介质的三分量记录上也出现了各种波的反射同相轴。为此，在实验室进行了多波多分量地震物理模型实验，以解释这种现象出现的原因。采用纵波和横波换能器作为模型实验的震源和接收器，并通过将横波换能器的偏振方向转动90°来获得九分量的观测方式。设计了均匀各向同性层状介质和倾斜介质物理模型，利用纵测线和非纵测线得到了多波多分量的观测记录。对观测记录分析发现，平层模型纵测线观测时，在PP,PSV和SVSV分量上都可以看到P波、转换SV波和SV波，这从另一方面说明，无论是P波震源还是S波震源都会产生P波和S波；平层模型采用非纵测线观测时，也能在各分量上得到各种波的反射；倾斜模型用P波震源激发，在SH分量上能接收到P波或SH波反射，这是因为P波和S波在SH分量上有振动分量。

P-wave or SV-wave reflection events can often be found in SH-component of three-component reflection records excited by P-wave source, which usually was thought to be cause by subsurface unhomogeneity or anisotropy. However, reflection events of all kinds of waves in three-component records can still be observed in homogeneous isotropic media. We use P-wave and S-wave transducers as source and receiver respectively, and we can acquire nine-component observation method by rotating the polarization direction of the S-wave transducer by 90°. Single-shot multiwave-multicomponent records are acquired on physical models of homogeneous isotropic stratified and oblique media with both in-line and out-of-line methods. The experiments indicate that when P- wave or S-wave source propagates in elastic media, S-wave or P-wave will be produced besides the main vibration P-wave or S-wave. Even in isotropic media, reflection events of these waves can still be obtained in records of various components when using out-of-line method on plane model. And the reason that P-wave or SH-wave reflection events can be found in SH component of three-component records excited by P-wave source on oblique model is that there is vibration component of reflection p-wave and S-wave on SH component.P-wave or SV-wave reflection events can often be found in SH-component of three-component reflection records excited by P-wave source, which usually was thought to be cause by subsurface unhomogeneity or anisotropy. However, reflection events of all kinds of waves in three-component records can still be observed in homogeneous isotropic media. We use P-wave and S-wave transducers as source and receiver respectively, and we can acquire nine-component observation method by rotating the polarization direction of the S-wave transducer by 90°. Single-shot multiwave-multicomponent records are acquired on physical models of homogeneous isotropic stratified and oblique media with both in-line and out-of-line methods. The experiments indicate that when P- wave or S-wave source propagates in elastic media, S-wave or P-wave will be produced besides the main vibration P-wave or S-wave. Even in isotropic media, reflection events of these waves can still be obtained in records of various components when using out-of-line method on plane model. And the reason that P-wave or SH-wave reflection events can be found in SH component of three-component records excited by P-wave source on oblique model is that there is vibration component of reflection p-wave and S-wave on SH component.