SEISMIC VULNERABILITY ASSESSMENT USING THE HVSR METHOD AT YOGYAKARTA INTERNATIONAL AIRPORT UNDERPASS, INDONESIA

Abstract

The Underpass at Yogyakarta International Airport (YIA) is in the Temon District, Kulon Progo Regency, Yogyakarta Province, Indonesia. The YIA has become one of the focal points for national infrastructure development and economic growth. Based on historical seismic activity, YIA and its vicinity are characterized by high levels of seismic activity. However, the data and information available regarding this matter are notably limited. This research aims to assess the soil vulnerability in the vicinity of the YIA Underpass. The soil vulnerability assessment is conducted by measuring microtremors and groundwater levels. The microtremor data is processed using the Horizontal-to-Vertical Spectral Ratio (HVSR) method with geopsy software and guidelines provided by Site Effects Assessment Using Ambient Excitations (SESAME). The research findings reveal that the study area exhibits a high seismic hazard potential, as evidenced by the seismic vulnerability index (K_g), which is more than 20. The interpretation of the HVSR curve indicates that the study area is characterized by a low dominant frequency (f₀) ranging from 0.214 to 0.289 Hz, along with varying shear wave velocities. Based on the stress-corrected shear wave velocity (V_s1), point U01 is more likely to liquefy than U05 and U07 as V_s1 in some soil layers is less than 215 m/s. This analysis indicates that the study area is susceptible to earthquake hazards due to thick soil deposit layers and shallow groundwater levels.