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

**Yu Liu and Guofeng Liu \***

School of Geophysics and Information Technology, China University of Geosciences (Beijing), Beijing 100083, China; 3010200013@cugb.edu.cn

**\*** Correspondence: liugf@cugb.edu.cn

**Abstract:** Passive-source exploration is a method of seismic exploration that has loose requirements on the conditions of the surface, is cheap, and does not require excitation by an active source. The ambient seismic signals collected from the field over an extended period of time can be used to generate virtual-shot seismic records similar to those obtained from the seismic exploration of an active source based on the relevant correlations, and this can in turn yield information on the underground structure through a series of conventional methods of processing seismic data. Threedimensional (3D) processing can mitigate the influence of the azimuth of random noise to yield a more representative underground structure, but requires intensive computation. In this paper, we propose a 3D method to compute reflections of a passive source based on the geometry of seismic exploration. Assuming a high quality of imaging, we use information on the predesigned geometry to choose and correlate noisy synthetic data on the reflections by a seismic body to create virtual shot data, and subsequently capture images of the 3D data on passive reflection. The use of the predesigned geometry ensures that only the important and useful parts of the dataset are used for correlation and imaging, where this reduces the cost of computation. The proposed method can thus efficiently generate high-quality 3D synthetic data.

**Keywords:** correlation; direct migration method; generation of virtual shot records; geometric design; passive seismic exploration
