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在复杂近地表条件下采集的地震资料,由于地形起伏剧烈、低降速带变化大,采用传统的铅垂时移静校正方法使地震波场发生扭曲,不利于波动方程偏移成像。本文提出了一种近地表层析反演与波场延拓联合基准面校正的方法,解决复杂近地表条件下采集地震资料的静校正问题。首先是利用折射波层析反演得到近地表模型;其次是炮检点波场延拓。将基准面置于地形之上,根据惠更斯—菲涅尔原理和波场互易原理以及炮检点的空间分布位置,以地表上接收的地震数据为二次震源,将炮检点分别先向下、后向上延拓到地表之上的水平基准面上,从而实现复杂近地表条件下,地震数据层析反演与波场延拓联合基准面校正。
Seismic data collected under complicated near-surface conditions have distorted the seismic wave field by the traditional method of vertical time-shift static correction, which is not conducive to the migration imaging of wave equation due to the dramatic fluctuation of the terrain and the large variation of the low-speed deceleration zone. In this paper, a method of near surface tomography inversion and wavefield continuation joint datum correction is proposed to solve the problem of static correction of seismic data acquired under complex near-surface conditions. The first is the use of refraction tomography inversion of the near surface model; followed by the gun point wavefield extension. According to the principle of Huygens-Fresnel and wave-field reciprocity, and the spatial distribution of the gunpoint, the seismic data received on the earth’s surface is taken as the secondary source. And then extend upward to the horizontal datum above the earth’s surface so as to realize the seismic data tomography inversion and the wave field continuation joint datum correction under complex near-surface conditions.