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我们从帝汶海的地震数据评估几种处理方法适应由高度不规则水底引起的复杂近地表速度场的能力。在存在大的横向速度变化的地区,常规处理是不适用的。一种方法是以较高速度的物质来替代水层并重新计算地震旅行时,这样可以有效地去除不规则水底的影响。然后,常规处理可以很成功地继续做下去。水层替代静校正技术是计算校正时移的一种简单而有效的方法。在波动方程层替代技术中应用了一种更为精确的算法来补偿近地表速度场的波传播效应。与那些只应用常规处理技术得到的剖面相比,两种水层替代处理技术得到的剖面不但提高了反射界面的连续性而且构造畸变也小了。尽管在给出的例子中两种方法所得到的结果是相似的,但通常选择波动方程方法,这是因为它在旅行时校正计算时要更实际一些。作为不同于水层替代方法的另一种方法,叠前深度偏移(PSDM)可用于不规则水底地形地区地震数据的成像。然而,PSDM对用于偏移的层速度模型很敏感。为了得到PSDM计算成本合理的结果,我们必须做大量的工作来获得一个层速度模型。在本项研究中,我们用一种迭代偏移/线性反演方法建立起一个精确模型。基于这个模型,PSDM生成的地震剖面要优于替代技术生成的剖面。为了进一步改进复杂近地表速度场地区PSDM的结果,我们认为要把高分辨率反射层析方法与建模处理结合起来。
We estimate from seismic data in the Timor Sea several approaches to the ability to adapt to complex near-surface velocity fields caused by highly irregular bottoms. In areas where there is a large lateral speed change, conventional handling is not applicable. One method is to replace the water layer with a higher velocity material and recalculate the earthquake travel, which effectively removes the effects of irregular water bottoms. Then, the routine can be successfully done. Aqueous layer replacement static correction technique is a simple and effective method to calculate the correction of time shift. A more accurate algorithm is applied in the wave equation layer replacement technique to compensate the wave propagation in the near-surface velocity field. Compared with the profiles obtained by using only conventional processing techniques, the profile obtained by the two water layer replacement techniques not only improves the continuity of the reflection interface but also reduces the structural distortion. Although the results obtained by the two methods are similar in the examples given, the wave equation method is usually chosen because it is more realistic to correct the calculations while traveling. As an alternative to water layer replacement methods, prestack depth migration (PSDM) can be used to image seismic data in irregular submarine terrain. However, PSDM is sensitive to the layer velocity model used for migration. In order to get a reasonable cost result for PSDM calculations, we have to do a great deal of work to get a layer velocity model. In this study, we used an iterative offset / linear inversion method to establish a precise model. Based on this model, the seismic profile generated by PSDM is superior to that generated by alternative technologies. In order to further improve the results of PSDM in complex near-surface velocity fields, we think it is necessary to combine high-resolution reflection tomography with modeling.