Identification and extraction of surface waves for the Bogota basin

Bogota is located above a geometrically complex lacustrine basin in a moderate-seismicity zone. This basin has deep low shear wave velocities, which can significantly amplify seismic ground motions and generate surface waves. Surface waves have caused substantial damage during earthquakes, resulting in intense shaking of buildings and other structures. Therefore, the characterization of these surface waves is crucial in earthquake engineering, particularly in densely populated and urbanized cities like Bogota. Previous studies have analyzed surface waves recorded at this basin, identifying long-period surface waves from time–frequency representations. However, no study has used the polarization differences among Rayleigh retrograde, Rayleigh prograde, and Love waves to identify these surface waves nor extracted the related time series from the original recordings from Bogota. This study constitutes the first effort to identify and extract three types of surface waves: Rayleigh retrograde, Rayleigh prograde, and Love waves, from seismic recordings in the Bogotá basin. The NIP methodology was used to understand better their polarization and contributions to ground motion. The results show that the extracted surface waves consistently exhibit longer mean periods than the original seismic records. Love waves were observed more frequently and contributed more to the ground motion intensity than Rayleigh waves. The presence of Rayleigh waves in the records varies by source type; for some types, it depends on the source characteristics, while for others, their existence relates to the station’s position within the basin. The duration of ground shaking was significantly influenced by surface waves, especially Love waves, with variations depending on source type and station location. While the NIP methodology was effective, challenges arose in extracting waves when different types of waves significantly overlapped or had weak polarization. Future research could expand the dataset to include more seismic events, particularly those with higher magnitudes, and explore the role of geological features like the Suba Hills and Eastern Andes in the surface wave propagation characteristics. This study aims to enhance the understanding of surface wave behavior and support advancing seismic hazard models in Bogotá.