The topographic-based vs30 model of the Opak River basin Yogyakarta

Background: Accurate v<inf>s30</inf> values are crucial for earthquake hazard assessment. The ongoing development of the v<inf>s30</inf> Model aims to yield the most precise representation of field conditions. Geological characteristics such as elevation, slope, and land development parameters are crucial. The Opak River area is located in the boundary of Young Merapi Deposit Group and the Southern Mountains litological units. This area has a history of seismic activity, notably the 2006 Yogyakarta earthquake. Purpose: The research aims to develop a v<inf>s30</inf> model based on geological and topographic parameters. Methods: The v<inf>s30</inf> reference data relies on v<inf>s30</inf> microtremor data, validated through MASW, N-SPT, and seismic borehole data. Validation v<inf>s30</inf> microtremor data with MASW yields a correlation coefficient of 0.98, while the correlation coefficient for the v<inf>s30</inf> microtremor profile with N-SPT ranges from 0.68 to 0.98. Both v<inf>s30</inf> microtremor and seismic borehole data categorize sites similarly. Results: The v<inf>s30</inf> model's development employs multiple regression with topographic parameters (elevation, slope, Terrain Ruggness Index and Topographic Position Index). The modeling process yields four v<inf>s30</inf> equation models with multiple regression coefficients ranging from 0.82 to 0.99. Conclusion: This model is expected to be applicable to seismic vulnerability models for earthquake preparedness and civil engineering practices.