SHEAR WAVE VELOCITY MODEL USING HVSR INVERSION BENEATH BANDA ACEH CITY, INDONESIA

Abstract

Near-surface shear wave velocity is one of the crucial parameters in earthquake-resistant building development. Therefore, this study aims to map the shear wave velocity profiles in Banda Aceh City-Indonesia, as the city is founded on a relatively thick Holocene sedimentary layer and experienced devastating damage during the 2004 earthquake. The method used in this study is the horizontal-to-vertical spectral ratio (HVSR) method. This method collects single-station microtremor data, which is processed by the HVSR method and then inverted so that a 1D profile of shear wave velocity is obtained. The results show that up to a depth of ~200 meters, the sub-surface layer in the Banda Aceh City is composed of soft to hard soil with shear wave velocity (Vs) values below ~750 m/s. In addition, the site's natural frequency within the city of Banda Aceh is from 0.74 to 1.94 Hz, indicating the presence of a fairly thick and deep soft layer. The combination of relatively low shear wave velocity (Vs) values and low site natural frequencies indicates that the Banda Aceh City area has significant seismic amplification potential. In addition, if the sub-surface soil materials are composed of coarse-grained soils and saturated, most of the soil layers in Banda Aceh City could also potentially experience liquefaction or excessive ground subsidence following an earthquake. A general precaution must be considered in applying the findings of the present study for further studies or actions, as several limitations are inherited in the geophysical method applied in the present study.