Comparison of different local site effect estimation methods in site with high thickness of alluvial layer deposits: a case study of Babol city

During earthquake loading, seismic evaluation of site dynamical analysis is the most serious issue in geotechnical earthquake engineering. Seismic waves pass through soils and rocks to reach the ground surface; hence, their characters play an important role in surface strong ground motion parameters. There are numerous techniques for the estimation of local site effect. This study aims at the comparison of different local site effect estimation methods in Babol city, Iran, with high thickness of the alluvial layer (80 m). Babol strong motion records have been used in this study. The obtained results from strong ground motions data were compared with other methods. The results reveal that for a site with high thickness of alluvial layer deposits, the microtremor measurement method is the best way for estimating site effect. Moreover, the numerical site response analysis based on the International Building Code and National Earthquake Hazards Reduction Program may not provide accurate results for alluvial layers at deep solid foundation, where an obvious rock-soil interface cannot be detected within 30 m.