Seismic Interferometry with Ambient Noise from Mizil Area, Romania

Abstract

The Green’s function between two receivers could be retrieved using seismic interferometry (SI) with ambient noise. The retrieval of surface waves has proved easy and robust. The retrieval of reflections has been more difficult and successful results have been demonstrated only lately. It has been shown that to retrieve reflections, the surface waves should be suppressed or eliminated during recording. Even though reflections were retrieved, their frequency content was lower then the frequency content of active data from the same sites. We applied SI to six hours of ambient noise recorded in the Mizil area, Romania, aiming at obtaining subsurface reflectivity without active sources. The site was chosen as relatively little anthropogenic surface-waves sources were expected. To further suppress the undesired retrieval of surface waves, the recorded noise was divided into parts dominated by surface waves and parts without dominant surface waves. We applied SI reflection-retrieval procedure to the parts, in total four hours, without dominant surface waves, which resulted in retrieval of nearly horizontal arrivals. We compared these arrivals with active data from the same area and confirmed the retrieved events to be reflections, including reflections from two geological markers, with frequency content comparable with the active-data one.