一维速度结构的地震波全波形反演理论测试

A Synthetic Study on Full Seismic Waveform Inversion for One Dimensional Velocity Structure

为了验证地震学研究中全波形反演方法的有效性,并研究其收敛特点,编写基于共轭梯度法的一维地震波全波形反演程序。首先使用单个震源和台站反演出一维非均匀速度结构,然后通过改变此过程中的各个条件,讨论不同因素对反演结果的影响。结果显示,全波形反演在数据较好的情况下能够得到很精确的反演结果;震源和台站是影响反演的最主要因素;多尺度反演以及更好的初始模型能够有效地提高反演的稳定性;观测数据的噪声可使结果产生小尺度的波动,但在大尺度上对结果的影响相对较小。

A conjugate gradient full waveform inversion program is coded to verify the effectiveness of full seismic waveform inversion and to study its characteristics. Firstly, a one dimensional inhomogeneous model is inverted using one source and one receiver. Then, by modifying different parameters of the inversion, the factors that affect the inversion result are discussed. It is shown that full waveform inversion can produce accurate result when data is abundant. The number of sources and stations is the primary factor that affect the inversion result. Multiscale inversion and better initial model can significantly improve the stability of the inversion. Noise applied to the observed seismogram can cause small scale disturbance on the result, though large scale characteristics of the result remain more or less unaffected.