频率域电磁场偏移成像

Migration of electromgnetic wave field in frequency domain

电磁场编移是研究观测电磁场的上行波场，是以反向扩散传播方式使各个场源逐渐归位的。若向下传播的偏移场的相位与原来上行波场的相位在介质的分界面上相同，则通过电磁场偏移成像能够恢复地球内部反射场的相位。本文讨论的问题是建立在激发源为平面电磁波基础之上的，当然此方法也可以应用于一般地面激发的可控源问题。文中采用有限差分方法进行编移成像，不仅可以确定地下电阻率异常的位置，而且还能反映电阻率异常的相对大小。理论试算的结果表明，效果十分明显。

The migration of electromagnetic wave field involves both analysing the upgo-ing waves of observed electromagnetic wave field and recovering the correct loca-tions of exciting sources by inverse propagation. We can make the migrated electro-magnetic wave field recover phase property of reflection wave field inside the earthon condition that the phase of downgoing migrated wave field and the phase of theoriginal upgoing wave field are equal at medium interface. The problem we discussis based on plane wave excitation. Of course, the method may also be applied toproblem relating to usua1 seismic vibrator on surface. Applying finite difference tomigration can locate resistivity anomaly and show the relative magnitude of the re-sistivity anomaly. Theoretica1 result proves the Ynethod very effective.