Abstract

This paper reviews the development and applications of the high-frequency multi-channel analysis of surface waves method (HF-MASW) for proximal soil sensing. The HF-MASW method uses surface waves to noninvasively measure soil profile in terms of the shear (S) wave velocity as a function of depth. Recently, several practical techniques have been developed to enhance the HF-MASW method, including (1) the self-adaptive method using a variable sensor spacing configuration, (2) the phase-only signal processing, and (3) a nonlinear acoustic technique. Using this enhanced HF-MASW method, the S-wave velocity soil profiles from a few centimeters to a few meters were measured. Fundamentally, the S-wave velocity is related to soil mechanical and hydrological properties through the principle of effective stress. Therefore, the measured 2-dimeniaional S-wave velocity profile images can reflect the temporal and spatial variations of soils due to weather effects, geological anomalies, and anthropologic activities. In this paper, several HF-MASW applications were described, including (1) measuring soil profiles, (2) studying weather and seasonal effects, (3) capturing the instantaneous variations of soil profiles during rain events, (4) detecting and imaging fraigpan layers, and (5) studying and imaging farmland compaction. These studies demonstrated that the HF-MASW method can be used as an effective proximal soil sensing tool for agricultural and environmental applications.