Preliminary Result: Analysis of Dominant Frequency in Western Part of Java, Indonesia using Hilbert-Huang Transform-HVSR Method

Abstract

The western part of Java is situated near various geological formations stemming from the collision between the Indo-Australian and Eurasian tectonic plates. These formations include the Java Trench, Sunda Strait, and several active onshore faults, rendering the area susceptible to seismic activity. The dynamic response of the soil to seismic shaking in this region warrants thorough investigation, particularly due to the prevalence of alluvium deposits in certain areas, which have the potential to amplify ground motion. In this research endeavor, seismic data recorded by 81 temporary seismic stations in West Java were utilized. The analysis employed the Hilbert-Huang Transform technique in conjunction with the Horizontal to Vertical Spectral Ratio (HVSR) method to derive the Horizontal-to-Vertical (H/V) spectral response curve for each measurement point. The implementation of the Hilbert-Huang Transform served the purpose of mitigating non-stationary transient noise commonly encountered in urban measurements, thereby enhancing the accuracy of the HVSR curve in portraying the dominant frequency characteristics of the measurement area. The findings of this study reveal that within the western part of Java, the dominant frequency values fall within the range of 0.9 to 7 Hz. Areas exhibiting lower dominant frequencies are indicative of a greater sediment thickness, predominantly observed in the northern region of the western part of Java, the Bandung Basin, some areas surrounding active volcanoes as well as various locales within the province of Banten.