Quaternary Sediment Thicknesses, Paleochannels, and Hazard Assessment Revealed by a 6200-Station Array in the Guangdong–Hong Kong–Macao Greater Bay Area, South China

ABSTRACT The Guangdong–Hong Kong–Macao Greater Bay area, a highly populated region, plays a vital role in the economic development of East Asia. Its construction and development rely on accurately characterizing near-surface loose sediment layers. However, traditional drilling and active source methods are often impractical for large-scale exploration in densely populated areas due to their high costs and destructive nature. To overcome this shortage, a dense array comprising 6214 stations was deployed and the noise horizontal-to-vertical spectral ratio method was employed to determine the fundamental frequency (f0) and peak amplitude. The Quaternary sediment thickness was further estimated based on their empirical relationships with f0. More importantly, several buried paleochannels were identified, manifesting deep valleys on the vertical section and curved stripes on the horizontal section. Combining regional drilling data and sites of geological hazards in the past, we conclude that the paleochannels are zones of high seismic and geological hazard. This study provides a scientific basis for urban construction and disaster prevention.