人工源宽角地震实验的谱元法模拟和逆时偏移成像方法研究

Spectral Element Simulation Method and Reverse Time Migration Research of Wide-angle Seismic Test

摘要:

人工源宽角反射（折射）地震资料具有偏移距较大、信噪比较低等特点，通常用于地震波走时反演重建地壳速度结构。逆时偏移成像方法作为勘探地震学领域获取地下构造形态的有效手段之一，可以有效弥补走时反演方法的不足。本文针对大偏移距宽角反射（折射）地震实验，利用四边形网格谱元法进行波场模拟，结合了有限元法的灵活性和谱方法的指数收敛性，高效且高精度获取模型合成地震记录，后采用逆时偏移成像方法将合成地震记录偏移归位，获取地壳几何结构，验证了逆时偏移成像方法在宽角地震资料处理及结果解释中的适用性，为后期实际地震资料的偏移成像提供了理论依据和支持。

Abstract:

Artificial source wide-angle reflection/refraction seismic data has the characteristics of large offset and low signal to noise ratio. The crustal velocity is usually reconstructed by seismic wave traveltime tomography. As one of the effective methods to obtain the underground structure in the field of exploration seismology,the reverse time migration imaging method can effectively make up for the lack of traveltime inversion methods. In this paper,the wave field simulation of the large-offset wide-angle reflection/refraction seismic test is carried out by using the spectral element method based on quadrilaterals. This method combines the geometrical flexibility of the finite element method and the exponential convergence rate associated with spectral method,which is believed to be an important method of seismic wavefiled modeling owing to its high efficiency and high accuracy. After the seismic records are obtained,the synthetic seismic records are migration homed by the reverse time migration imaging method,and the geomorphic structure of the crust is obtained. The results show that the reverse time migration is suitable for the interpretation of wide-angle seismic data,which provides the theoretical basis and support for the migration imaging of the actual seismic data.