Comparative Evaluation of Site Response Analysis Methods in Lima City: Case of the 2021 (M w 6.0) Mala Earthquake

The seismic response evaluation of soil deposits in Metropolitan Lima requires analysis methods that can capture local amplification effects, owing to the region’s complex alluvial stratigraphy and high seismicity. This study performs a comparative assessment of four site response analysis methods using records from the 2021 Mala (M w 6.0) earthquake, located south of Lima: (1) normative amplification factors (NAF E.030), (2) ground motion models (GMM), (3) average amplification factors (AAF), and (4) one-dimensional wave propagation analysis (1DPA). Performance was evaluated using root mean square error (RMSE) between observed and predicted response spectra as the primary accuracy metric. A total of 31 accelerographic stations were analyzed, classified by time-averaged shear wave velocity of the top 30 m soil layers (V s 30) into three categories: stiff (S1’: 550–800 m/s), intermediate (S2 ′ : 350–550 m/s), and soft (S3’: 200–350 m/s) soils. Linear elastic soil behavior was confirmed through 1DPA, indicating maximum shear strains below 0.01% across all sites, well within the elastic threshold. The results revealed that 1DPA analysis produced the most accurate estimates, with average RMSE values of 27.4 cm/s 2 for S1’ soils and 38.5 cm/s 2 for S2’ soils. NAF E.030 performed well in 8 out of 10 stiff soil sites (RMSE =33.1 cm/s 2 ), however, exhibited significant limitations in softer soils where RMSE values exceeded 37 cm/s 2 . GMM and AAF methods demonstrated RMSE values ranging from 44.8 to 51.4 cm/s 2 , with reduced accuracy in long-period ranges (>1.0 s) and S3’ soil sites. These findings highlight the need to revise current normative amplification factors for soft soils and support the implementation of 1DPA analysis in areas with complex stratigraphy or deep sedimentary deposits, thereby contributing to improved seismic-resistant design practices in Metropolitan Lima.