利用qP波慢度和偏振矢量计算弱各向异性介质参数

Calculation of weakly anisotropic parameters by slowness and polarization vectors of qP wave

提出了一种使用慢度矢量分量和偏振矢量计算变井源距垂直地震剖面(walkawayVSP)钻孔中接收点附近介质弱各向异性(WA)参数的方法.假定介质是任意弱各向异性介质,从一般公式中得到了只有一条观测剖面情况下的反演公式.如果知道了慢度矢量的垂直分量和偏振矢量,可以通过反演得到与剖面和钻孔所在平面相关的WA参数,反演过程不用进行射线追踪,与上覆介质无关.用合成数据检验了公式和方法的正确性,并把它们应用于在爪哇海地区得到的一条变井源距垂直地震剖面的弱各向异性参数反演中.

An algorithm is proposed for local evaluation of weakly anisotropic （WA） parameters from measurements of slowness vector components and parti- cle motions of qP waves at individual receivers in a borehole of walkaway verti- cal seismic profile （VSP） experiment. Formulae for a special case of a single VSP profile are obtained under the assumption of weak but arbitrary anisotropy of the medium. The knowledge of＇a single component of the slowness vector and the polarization vector is sufficient for performing an inversion in a medium with an arbitrary overburden. A synthetic test is carried out to verify the cor- rectness of the formulae and the method is applied to the observed data from the Java Sea region to invert for the WA parameters in the borehole.