Elsa Fadlika Widyantari, Mochamad Aryono Adhi, Ilqia Rahma, Nugroho Budi Wibowo, Desi Mustami' Limayukha, Bilqis El Farsiyyi, Rahmania Sofyana Ulya

Evaluation of Seismic Vulnerability Index and Soil Classification in Sleman Regency Based on Microtremor Analysis and the HVSR Method

Introduction

Evaluation of seismic vulnerability index and soil classification in sleman regency based on microtremor analysis and the hvsr method. Assess seismic vulnerability & soil classification in Sleman Regency, Yogyakarta, using microtremor & HVSR. Reveals low to moderate damage potential & soil types for resilient urban planning.

Abstract

Kalasan District and Ngemplak District, located in Sleman Regency, Yogyakarta, are areas with significant seismic risk due to the subduction of the Indo-Australian and Eurasian plates south of Java Island. To support disaster mitigation and land-use planning, it is essential to understand the local geological structure and soil dynamic response. This study aims to evaluate the seismic vulnerability and soil classification using the Horizontal to Vertical Spectral Ratio (HVSR) method and Rayleigh wave ellipticity inversion modeling. Microtremor measurements were conducted at 27 points distributed across both districts. The HVSR method was used to obtain the dominant frequency and amplification values, while the ellipticity inversion of Rayleigh waves was employed to estimate the shear-wave velocity profile and calculate Vs₃₀ values. The results show that the dominant frequency ranges from 0.713 Hz to 18.006 Hz, amplification values range from 0.569 to 4.193, and the seismic vulnerability index ranges from 0.010 to 12.060. Based on these parameters, Sleman Regency is generally categorized as having low to moderate seismic damage potential due to the relatively low amplification and vulnerability index. The Vs₃₀ values indicate a variation in soil site classes, namely medium-density soil (SD) and very dense soil (SC). These findings provide essential data for seismic microzonation, contributing to more resilient urban development strategies.

Review

This study provides a valuable and timely evaluation of seismic vulnerability and soil classification within Kalasan and Ngemplak Districts of Sleman Regency, an area critically exposed to seismic hazards from active plate subduction. The research effectively addresses a significant gap by offering detailed insights into local geological structures and soil dynamic responses, which are paramount for effective disaster mitigation strategies and responsible land-use planning. The chosen methodology, integrating the Horizontal to Vertical Spectral Ratio (HVSR) method with Rayleigh wave ellipticity inversion modeling from microtremor data, represents a robust and well-established approach for comprehensive seismic hazard assessment at a localized scale. The methodology involved meticulous microtremor measurements conducted at 27 strategically distributed points across both districts. The HVSR method was successfully employed to ascertain dominant frequency and amplification values, while ellipticity inversion of Rayleigh waves facilitated the estimation of shear-wave velocity profiles and Vs₃₀ values. The empirical findings reveal a dominant frequency range from 0.713 Hz to 18.006 Hz, amplification values spanning 0.569 to 4.193, and a seismic vulnerability index between 0.010 and 12.060. Critically, these parameters lead to the conclusion that Sleman Regency generally exhibits low to moderate seismic damage potential, primarily due to the relatively subdued amplification and vulnerability indices. Furthermore, the Vs₃₀ values effectively categorize the soil site classes as predominantly medium-density soil (SD) and very dense soil (SC). The findings of this research offer essential and actionable data for the development of seismic microzonation maps in Sleman Regency. By providing a precise characterization of site-specific soil conditions and their potential seismic response, the study significantly contributes to fostering more resilient urban development strategies. This detailed geophysical investigation is invaluable for informing engineers, urban planners, and local authorities, enabling them to make informed decisions regarding infrastructure design, building codes, and emergency preparedness. Ultimately, this work stands as a strong example of how localized seismic assessments can directly enhance public safety and contribute to the long-term sustainability of communities in seismically active regions.

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