In-Situ Seismic Characterization and Interpretation of Dynamic Properties of Peat Soils Using MASW and Seismic Refraction

Abstract Dynamic soil properties play a crucial role in ground response analysis. However, their reliable determination remains challenging for peat soils due to severe sample disturbance during laboratory testing caused by stress relief, very high water content, high compressibility, and fibrous structure. These limitations necessitate a more robust in-situ evaluation of peat dynamic behavior. This study investigates the in-situ dynamic properties of peat soils in Southern Peninsular Malaysia using Multichannel Analysis of Surface Waves (MASW) and Seismic Refraction (SR), with emphasis on comparative interpretation and correlation with peat physical characteristics. The shear wave velocity (V s ) obtained from MASW ranges from 24.5 to 34.5 m/s, while SR yields higher values ranging from 29.9 to 48.3 m/s. A systematic comparison shows that SR consistently overestimates V s relative to MASW by approximately 12–26%, highlighting the influence of wave propagation mechanisms and method-specific assumptions when applied to highly organic soils. The derived maximum shear modulus (G max ) and maximum elastic modulus (E max ) range from 0.4 to 1.45 MPa and 1.21 to 4.34 MPa, respectively, and are of similar order of magnitude to those reported in previous studies. Beyond parameter estimation, the study demonstrates clear correlations between dynamic properties and key peat characteristics, including moisture content, organic content, fibre content, and bulk density, providing interpretative insight into the factors governing peat stiffness at small strains. The findings show that MASW and SR, when used comparatively and interpreted alongside peat physical properties, offer a reliable and sustainable framework for in-situ dynamic characterization of peat soils for engineering analysis.