Evaluating Liquefaction Susceptibility Through HVSR and MASW Methods: A Case Study in Mamuju, West Sulawesi, Indonesia

Abstract

The 2021 Mamuju earthquake (Mw 6.2) highlighted the region’s high vulnerability to liquefaction due to its proximity to active tectonic zones, as well as the presence of Holocene alluvial deposits, unconsolidated sedimentary formations, and water-saturated soils, all of which contribute to high susceptibility to seismic shaking. This research assesses the liquefaction potential of the Mamuju area using an integrated approach that combines the Horizontal-to-Vertical Spectral Ratio (HVSR) and Multichannel Analysis of Surface Waves (MASW) methods. This study investigates an inverse correlation between Vs30 and the seismic vulnerability index (Kg), where lower Vs30 values correspond to higher Kg values, indicating increased liquefaction susceptibility. The HVSR analysis shows that the dominant frequency (f0) ranges from 0.4 to 11 Hz, while the amplification factor (A0) varies between 1.1 and 11. The results indicate that coastal zones with thick alluvial deposits exhibit the lowest f0 values (<2.5 Hz), which correlate with Vs30 < 175 m/s and Kg > 10, suggesting a higher likelihood of liquefaction. Conversely, areas underlain by the Mamuju Formation and Adang Volcanics, characterized by higher Vs30 (>175 m/s), f0 (>10 Hz), and Kg (<10), show lower susceptibility. These findings contribute to developing a detailed microzonation map for liquefaction risk, which is essential for improved urban planning and disaster mitigation in Mamuju. This study demonstrates that integrating HVSR and MASW methods is an effective approach to characterizing soil properties and enhancing liquefaction risk assessment in seismically active regions.