P波偏振层析成像

P-WAVE POLARIZATION TOMOGRAPHY

论述了P波偏振层析成像方法 .这是一个利用P波远震偏振资料去反演速度结构的方法 ,与走时层析成像相比 ,它有几个显著的优点 :不受震源定位和发震时刻误差的影响 ;对深地幔速度结构不敏感而对接收器附近的速度结构和速度梯度最敏感 ,在这一意义上它与走时反演是互补的 .如果联合使用走时和偏振资料可以改善层析成像的结果 .走时的变化对应于速度的变化 ,而偏振的变化则与速度梯度的变化相对应 ,因此 ,要确定速度异常的边界 ,用偏振数据更合适 .三维数值模拟实验以及实际应用证实了P波偏振层析成像是一个有效的、实用的新颖方法 .

P wave polarization tomography is an invesion method that uses teleseismic P wave polarization data to obtain velocity structure. Polarization inversion has some intrinsic advantages over travel time inversion: It is not influenced by source location and origin time errors; it is not sensitive to deep mantle velocity structure but is more sensitive to near station velocity structure. Travel time responds to the velocity variation, while the polarization responds to the velocity gradient variation. The two types of data are complementary to each other in this sense, with polarization data better suited to delineate the edges of the velocity anomalies. Joint inversion of both P wave travel time and polarization direction data can improve the tomographic result. Numerical tests show that the polarization method is correct, numerically accurate, rapidly convergent and stable in the presence of measurement noise.