Comparative Analysis of Interrogator Unit Performance in Surface Seismic DAS: Case Study in a Campus Area

Summary This study investigates the effects of different interrogator units (IU) on surface seismic Distributed Acoustic Sensing (DAS) performance, through a comparative analysis. Seismic data was acquired using DAS IU X and Y that connected to a buried single mode fiber optic cable, alongside geophones as reference. The data analysis focuses on signal quality, noise characteristics, and phase velocity dispersion. Initially, the raw DAS datasets are dominated by common mode noise (CMN), which appears to be more severe and irregular patterns for DAS IU Y than DAS IU X, which appears to be more consistent at high frequency. After applying noise attenuation filters, both DAS datasets become more comparable to geophone data as the ground roll and direct arrival are more visible. Our velocity dispersion results shows that DAS IU X captures ground rolls event at a broader frequency spectrum (5 Hz – 45 Hz) compared to DAS IU Y, which is more focus on lower frequencies (7 Hz – 25 Hz). The dispersion curve for geophones spans 10 Hz to 35 Hz and is less smooth than DAS. Phase velocity analysis shows that DAS IU X is more suitable for high resolution surface wave analysis in shallow seismic imaging as it offers clearer and more continuous fundamental mode dispersion trend than DAS IU Y. These findings highlight the importance of interrogator selection in optimizing DAS-based seismic surveys.