A review of the high-frequency surface wave method for proximal soil sensing

Abstract

This talk will review the latest developments and past applications of the high-frequency multi-channel analysis of surface waves method (HF-MASW) for proximal soil sensing. The HF-MASW method uses surface wave propagations and spectral analysis 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 the past, several HF-MASW applications were conducted, including (1) soil profiling in the vadose zone, (2) a long-term-survey for studying weather and seasonal effects, (3) detecting and imaging fraigpan layers, and (4) a farmland study to assess the influence of compaction caused by the passages of a tractor. These study demonstrated that the HF-MASW method can be used as an effective proximal soil sensing tool for agricultural and environmental applications. Future work will be focused on developing a non-contact HF-MASW technique that can automatically and rapidly map farmlands.