Seismic microzonation of Bandung basin from microtremor horizontal-to-vertical spectral ratios (HVSR)

Bandung is located on a thick sedimentary basin, which is mainly composed of volcanic rocks and the depositional remnants of an ancient lake. The high population density and vital infrastructure, surrounding by potential sources of earthquakes make Bandung vulnerable to earthquake impact. To study the seismic response of Bandung, a microzonation study is needed so as to facilitate disaster risk assessment and mitigation. The parameters which are mapped for the purpose of microzonation are the distribution of the dominant frequency (F₀), the amplification factor (Am) and seismic susceptibility (Kg). We use the HVSR analysis method with microtremor/ambient seismic noise data. The microtremor data were taken from 58 measurement points from the Bandung Seismic Experiment network run from March to October 2014 in the Bandung basin and surrounding areas. The results show that the dominant peak frequency in the studied area ranges from 0.195 Hz to 7.016 Hz, amplification (A) spans from 1.6 to 11.3, and the value of the seismic susceptibility index (K_g) ranges from 0.6 to 245.6. The spatial distribution of seismic susceptibility index indicates that almost all areas of the Bandung basin have high susceptibility to earthquake hazard. The highest susceptibility is found in the eastern part of the Bandung basin that includes Bojongsoang, Rancaekek, Ciparay, Rancasari, and Majalaya, while the lower susceptibility zones are scattered in the hills and mountains around the basin of Bandung.