Classification and Evaluation Method for Complex Near-Surface Facies in Front of the Longmen Mountains

The near-surface of complex piedmont zones exhibits strong heterogeneity with significant variations in the thickness and velocity of low-velocity layers, which constitute key technical challenges in seismic exploration. This study proposes the concept, connotation and evaluation framework of near-surface facies, establishes a complete classification and evaluation workflow, and accurately divides the study area into 9 categories and 22 types of near-surface facies. The characteristics and spatial variation laws of near-surface facies are clarified from three dimensions, providing technical support for optimizing seismic exploration parameters. This research addresses the exploration challenges in the Longmen Mountains area and offers a valuable reference for similar studies in complex piedmont zones.