Subsurface Characterization Using Passive and Combined MASW Survey

Abstract

The Multichannel Analysis of Surface Waves (MASW) method has emerged as a valuable, non-invasive technique for site characterization and shear wave velocity (Vs) profiling. However, its application in complex, noise-prone urban terrains, such as the Itanagar Capital Complex, faces significant logistical and data quality challenges that limit the effectiveness of traditional survey setups. To address these constraints, this research presents a comprehensive optimization of passive roadside MASW surveys, focusing on analyzing site-specific effects and enhancing subsurface profiling reliability. The primary objectives were to optimize data acquisition and processing parameters, evaluate the influence of subsurface conditions on signal quality and validate a combined Active-Passive MASW approach to improve depth resolution and modal clarity. newlineField investigations were systematically conducted across six geologically diverse sites, where key parameters including receiver spacing, array length, offline distance and sampling frequency were varied to identify the most stable configurations. To overcome the inherent limitations of individual methods regarding depth penetration and frequency bandwidth, the study integrated high-frequency active data with low-frequency passive data. Advanced processing techniques, including dispersion image stacking and statistical inversion quality assessments, were employed to rigorously refine the resulting Vs models and ensure data robustness. newlineThe results identified a specific optimized configuration characterized by a 1 m receiver spacing and moderate offline distances (approximately 10 m) which consistently yielded the highest resolution and stability in dispersion imaging. The derived Vs profiles ranging from approximately 200 m/s in shallow layers to 1000 m/s at depth, were validated against independent borehole logs and Standard Penetration Test (SPT) data. This comparison confirmed the superior reliability of the combined MASW approach particularly in stratified subsurface conditi