Passive seismic reflection imaging based on acoustic and elastic reverse time migration without source information: theory and numerical simulations

Abstract

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.

Three-Dimensional Processing of Reflections for Passive-Source Seismology Based on Geometric Design

“…The passive-source direct migration method is another means to improve computational efficiency. It was proposed by Artman [28] and has been applied to passive seismic exploration [29][30][31][32]. The passive-source direct migration method does not generate correlations to obtain virtual shot records, but directly performs migration imaging to obtain records of random noise and improve computational efficiency.…”