To explore crustal structures using seismic records of earthquakes, we proposed a new seismic reflection imaging method based on reverse time migration (RTM) without source information. In the proposed RTM method using multiple reflections between surface and subsurface boundaries, we correlate forward- and backward-extrapolated wavefields of the same observation records from all receivers at once. We implemented acoustic RTM based on a scalar wave equation and elastic RTM based on a velocity-stress formulation for wavefield modelling. Furthermore, we adopted scalar and vector potential formulations in elastic RTM to obtain separate P- and S-wave reflection images. In our study, numerical simulations with a regional crustal structure model were conducted to compare combinations among the synthetic data by acoustic or elastic wave modelling, observation conditions, and RTM formulations. We demonstrated the validity of the proposed method with idealised dense observations and confirmed a limitation due to quasi-realistic sparse observations. Artefacts due to the mixture of P- and S-waves in the acoustic RTM images from elastic synthetic data were attenuated by elastic RTM, which addresses the proper illumination of P- and S-wave reflections.

为了利用地震的地震记录探索地壳结构，我们提出了一种基于逆时偏移（RTM）的地震反射成像新方法，无需震源信息。在提出的使用地表和地下边界之间的多次反射的 RTM 方法中，我们同时关联来自所有接收器的相同观测记录的前向和后向外推波场。我们实现了基于标量波动方程的声学 RTM 和基于波场建模的速度-应力公式的弹性 RTM。此外，我们在弹性 RTM 中采用标量和矢量势公式来获得单独的 P 波和 S 波反射图像。在我们的研究中，使用区域地壳结构模型进行数值模拟，以通过声波或弹性波建模比较合成数据之间的组合，观察条件和 RTM 公式。我们通过理想化的密集观测证明了所提出方法的有效性，并证实了由于准现实稀疏观测造成的局限性。由于来自弹性合成数据的声学 RTM 图像中 P 波和 S 波混合造成的伪影被弹性 RTM 衰减，这解决了 P 波和 S 波反射的适当照明问题。