Variability in receivers responses of MASW test on undulated grounds: A numerical perspective

Abstract

This article presents methodological and signal processing cautions associated with utilizing the multichannel analysis of surface waves (MASW) test for determining shear wave velocity (Vs) profiles on undulated ground surfaces. The past studies highlight that the conventional MASW test, which is suitable for flat ground surfaces, may not directly apply to undulated grounds with features like heave, crest, etc. Previous studies on MASW test lack an understanding of the influence of source and receiver positioning on various undulations. Three scenarios of ground undulations were created in GiD software and analyzed in the OpenSEES software framework. There were 12 receivers used for these ground undulations based on the Fourier amplitude spectrum attenuation. The receivers' responses (horizontal and vertical components of wavefields) from these ground undulations were analyzed through signal processing using cross-correlation, time-lag, and wavelet coherence. Notably, the undulated topography significantly impacted the vertical components of the wavefield. The phase angle variations from wavelet coherence could be used to determine the minimum frequency of the dispersion curve for these ground undulations. Significant variations in the phase velocity were observed at lower frequencies in the presence of ground undulations, while on a flat surface, they remained unaffected. The effect of under−/over-estimation of Vs (in the range of 50–100 m/s) was successfully demonstrated in each respective undulation with the methodological and processing cautions needed in the MASW analysis.