Use of Rayleigh Wave Velocity as a Parameter for Seismic Site Classification in Panama

Site classification, based on the dynamic behavior of soils, is fundamental for the study of seismic hazard. The proposed methodologies emphasize two key parameters: the shear wave velocity of the soil and the site’s vibration frequency, for site classification. For estimating shear wave velocity, the analysis of surface waves is widely used through surface vibration signals to determine Rayleigh wave velocities. Modeling this response estimates the shear wave velocity profile, and the site is classified according to the average velocity. In comparison, a site classification based directly on Rayleigh wave velocities reduces computational cost and model complexity. Rayleigh wave velocities represent a parameter that can be measured without involving the modeling of soil strata. The Rayleigh wave velocity depends on the dynamic properties of the soil from the surface to a certain depth and includes the overall behavior of the surface stratigraphy, making it directly useful for site characterization. Additionally, because the vibration frequency is a function of soil stiffness, Rayleigh wave velocity can be used to estimate the site’s vibration frequency. This study presents a site classification methodology based on the application of Rayleigh wave velocities as the primary parameter, as an alternative classification approach aligned with conventional methodologies based on shear wave velocity and site classification methodologies based on site vibration frequency. Its application in the field and at points of interest in Panama achieved results similar to those obtained through conventional methodologies with an absolute average margin of error of 6%.