弹性波高斯束叠前深度偏移

本文提出一种新的多分量地震成像方法--弹性波高斯束偏移，同以往的弹性波偏移（Kirchhoff偏移，逆时偏移）方法相比，兼具较高的成像精度与计算效率。该方法通过局部倾斜叠加将多分量地震记录分解为不同波型、不同初始方向的局部平面波，并利用弹性动力学高斯束的走时、振幅以及极性信息进行矢量波场的延拓成像。本文以二维弹性波Kirchhoff-Helmholtz积分为基础，推导了基于高斯束表示的弹性波波场反向延拓公式，然后利用互相关成像条件求取反射波以及转换波的成像值。针对转换波成像剖面中的极性反转问题，本文根据反射界面处转换波的传播以及偏振特点，给出了一种校正方法。最后，通过数值模型试算，验证了该弹性波成像方法的正确性和有效性。

Elastic Gaussian beam pre-stack depth migration

In this paper, we present a new method for multi-component seismic data imaging, called elastic Gaussian beam migration. Its imaging accuracy is higher than that of Kirchhoff migration, and its computational efficiency higher than reverse time migration. This migration method first decompose the multi-component data into local plane-wave components with different wave modes and different initial directions by local slant stacks, and then achieves downward-continuation imaging of the vector wavefield using the traveltime, amplitude and polarity of elasto-dynamic Gaussian beams. Based on 2-D elastic Kirchhoff-Helmholtz integral, we derive an elastic inverse wavefield extrapolation formula in terms of Gaussian beams, and extract the imaging result of reflected and converted waves using cross-correlation imaging condition. For the polarization reversal on converted waves imaging sections, we offer a correction method on the propagation and polarization of converted waves near the reflectors. We finally make trials on numerical models to prove the correctness and availability of the presented elastic migration method.