The recent increase in seismic activities around the world has led to the need for the development of seismic-resistant structures, including buildings, road bridges, dams, slopes, and earth-retaining structures. One of the primary steps in designing these structures is dynamic characterization. Dynamic characterization provides information about the dynamic behavioral properties of the soil and monitors the surface-level site response. This information is crucial in estimating the ground response and the seismic microzonation of a particular region.
The most commonly adopted technique for site characterization is using borehole data, which is too expensive. Therefore, the use of non-destructive geophysical techniques has been employed in recent years. Multichannel Analysis of Surface Wave (MASW) is a universally accepted geophysical technique to obtain the dynamic properties of subsurface materials. It is a practical, non-intrusive method that is accurate in predicting the shear wave velocity, which is used to determine parameters for engineering purposes.
MASW provides a one-dimensional profile of the subsurface layers of the soil beneath, giving a basis for the ground motion response, potential effects on liquefaction, and an idea of the natural frequency with soil amplifications during an earthquake event. The average shear wave velocity for the uppermost 30 m depth of the soil profiles is considered for the primary site classification under seismic conditions.
A recent study by Rangaswamy et al. (2023) focuses on assessing the dynamic characterization of underlain soil profiles for the spatially distributed sample sites across the study area (in the southern Calicut city nearby the NIT Calicut region) by calculating the average shear wave velocity Vs30 and classifying the site according to the National Earthquake Hazard Reduction Program (NEHRP) provisions. The shear wave velocity is used to evaluate the site response of the upper 30 m depth, with the distribution of the obtained values of Vs30 (e.g. Fig.1) demonstrating site classes of C and D, according to the NEHRP (National Earthquake Hazards Reduction Program) and IBC (International Building Code). These laws are similar to the NTC2018.
Several published papers discuss the site characterization with shear wave velocity profiles, ground response analysis, and micro zonation mapping (e.g. Joyner and Fumal, 1984; Sairam et al, 2019; Luna and Jadi, 2000, etc.; Fig.2).
In conclusion, dynamic characterization provides essential information that is crucial in designing earthquake-resistant structures. The use of non-destructive geophysical techniques, such as MASW, is practical and economically feasible. Its accuracy in predicting the shear wave velocity makes it a valuable tool in site characterization, ground response analysis, and micro zonation mapping.
See also our software about MASW: Multi-Channel Analysis of Surface Waves – Easy MASW