基于自适应震源子波提取与校正的瑞利波波形反演

近年来，基于瑞利波的全波形反演技术取得了较大进展，在接收点覆盖面积足够的情况下，该方法对横向不均匀复杂介质具有较高的分辨能力。影响波形反演精度的关键因素之一是震源子波，然而野外地震记录对应的地震子波是未知的，采用不正确的震源子波势必对反演结果产生负面影响，常规处理方法是利用合成数据进行子波校正，但子波校正需进行多次迭代，导致反演计算时间增加。为了解决这一问题，引入加窗自适应子波提取方法，从观测记录中提取与实际数据匹配较好的震源子波，将其作为初始子波进行子波校正，达到进一步优化反演结果的目的。分别采用真实子波、错误子波、错误子波联合子波校正、提取子波、提取子波联合子波校正五种子波对断层模型进行反演测试。测试结果表明：所提方法获得的子波对应的反演结果最好，错误的子波对应的结果最差；仅利用提取的子波也可以获得较好的反演效果，而采用子波提取与校正相结合的方法可以节省计算时间，进一步提高瑞利波波形反演的精度。最后通过实际数据测试进一步验证了该结论。

Waveform inversion based on adaptive source wavelet extraction and correction for Rayleigh waves

Full waveform inversion (FWI) based on Rayleigh waves has made significant advances in recent years. If the receiver coverage is adequate,FWI offers a high resolution in laterally heterogeneous complex media. Source wavelet is one of the key factors affecting the accuracy of waveform inversion. However,the seismic wavelet for field seismic record is unknown,and an improper source wavelet is bound to have a negative effect on inversion results. The conventional solution is extracting and correcting a wavelet with synthesized data. However,wavelet correction is time-consuming because it requires repeated iterations. To solve this problem,this paper proposes a windowed adaptive wavelet extraction method to extract a source wavelet that is in line with the actual situation from the observation records,use it as the initial wavelet for wavelet correction,and thereby achieve the purpose of further optimizing inversion results. Inversion tests on a fault model constructed are conducted with five wavelets,including the actual wavelet,a wrong wavelet,a wrong wavelet combined with wavelet correction,an extracted wavelet,and an extracted wavelet combined with wavelet correction,respectively. The test results show that the wavelet obtained by the proposed method corresponds to the best inversion result,while the wrong wavelet corresponds to the worst one. Although a favorable inversion effect can also be achieved with the extracted wavelet alone,combining wavelet extraction with wavelet correction can save computation time and further improve the accuracy of Rayleigh waveform inversion. More-over,field data application further verifies this conclusion.