Seismic technologies

[SE-05] Seismic imaging of deep crustal structures via reverse time migration using local earthquakes

*Kazuya Shiraishi¹, Toshiki Watanabe² (1. JAMSTEC (Japan), 2. Nagoya University (Japan))

We developed a seismic imaging method based on revere time migration (RTM) for exploring deep crustal structures using reflection waves of earthquakes without source information. Instead of wavefield extrapolation from both well-defined sources and receivers in a conventional RTM, only receiver-side wavefield extrapolation is required in the proposed method and forward- and backward-extrapolated wavefields of the same observation records from all receivers are correlated to illuminate multiple reflections between surface and subsurface boundaries. In this study, we present a two-dimensional numerical simulation to validate the proposed method with a regional crustal structure model with quasi-actual source locations and different receiver settings. We also show a case study of an application to actual records of a seismic network observation on land in Kanto region, Japan. The seismic reflection image along the 190-km pseudo-survey line using hundreds of surrounding local earthquakes shows continuous reflectors around 20 - 40 km in depth, which are likely part of the surface of the Philippine Sea slab. Our results suggest a potential for reflection imaging of deep structures by using the large energy of earthquakes. The proposed method may become a useful technique for imaging crustal structures and monitoring their conditions from huge amounts of seismic data recorded by high-dense seismic network observations.