Indonesia is a region with high seismic activity; therefore, subsurface soil characteristics need to be investigated to understand their response to earthquake waves. This study aims to determine the seismic characteristics of subsurface soils based on the dominant frequency (f₀), dominant period (T₀), amplification factor (A₀), seismic vulnerability index (Kg), and average shear-wave velocity to a depth of 30 meters (Vs30) in Pancur Batu District and Tarutung District using the Horizontal to Vertical Spectral Ratio (HVSR) method. Microtremor data were processed using Geopsy software to obtain the dominant frequency and amplification factor, while Vs30 was estimated through inversion using the Dinver module. The seismic vulnerability index was calculated using Kg = A₀/f₀, and site classification followed SNI 1726:2019. The results show that Pancur Batu has f₀ of 3.39854 Hz, T₀ of 0.29424 s, A₀ of 2.3885, Kg of 1.6786, and Vs30 of 455.70 m/s. Tarutung has f₀ of 2.33859 Hz, T₀ of 0.42761 s, A₀ of 3.09903, Kg of 4.1063, and Vs30 of 654.54 m/s. Both locations are classified as Site Class SC, although Tarutung exhibits a higher dynamic ground response due to differences in local geological conditions.
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