Seismic amplification, ground deformation, and damage in the 2021 Mamuju–Majene earthquake

The 2021 Mamuju–Majene earthquake (Mw 6.2) caused extensive structural damage in Mamuju. This study assessed the building damage distribution across the city of Mamuju using the damage index (DI) of the European Macroseismic Scale (EMS-98) and analysed its correlation with seismic amplification and ground deformation. The site response analysis utilised the Vs₃₀ of multichannel analysis of surface wave surveys, while seismic amplification factors were calculated through one-dimensional site response analysis. In addition, interferometric synthetic aperture radar (InSAR) analysis was employed to assess ground deformation. The findings reveal that short-period spectral amplification (0.2 s) and construction quality were the dominant factors in structural failures, particularly affecting low-rise buildings (1–3 storeys). In contrast, long-period amplification (1.0 s) exhibited a weaker correlation with the DI, likely due to the limited number of mid- and high-rise structures in the study area. While evidence of liquefaction was observed, its overall impact on building damage was less significant. The integration of InSAR-derived ground deformation, geotechnical site response analysis, and field-based damage data proved to be highly effective for post-earthquake forensic assessment. This combined framework enabled the simultaneous evaluation of seismic amplification and permanent ground deformation, offering a more holistic understanding of damage mechanisms than conventional single-discipline approaches.