Liquefaction Potential based on ground investigation data and natural frequency

Abstract An earthquake can trigger other disasters. Liquefaction is one of them and it occurs due to the reduction or loss of effective stress in soil due to cyclic loads. Liquefaction may cause the ground to act as a flowing liquid and become harmful to the building above it. Damage to a building’s structure can occur because of the strong surface waves from soil thrust and flow. Thus, an evaluation of the liquefaction potential is needed to prevent building damage. This study aims to determine the vulnerability of Padang City to liquefaction disasters and proposes a liquefaction potential based on the natural frequency at the surface. The study was conducted by analysing soil investigation data (54 CPT and SPT), using earthquake acceleration to obtain the value of the safety factor (SF), and single microtremor observations, to determine the natural frequency of the soil at these points. The results show that the form of liquefaction potential in Padang City varies depending on the depth of the reviewed soil. At a depth of 1 m, almost the entire research area has liquefaction potential. The coastal area has a very high level of vulnerability. In general, the liquefaction potential decreases with increasing depth. The liquefaction potential and the natural frequency of the soil (f0) are related; soil with an f0 value of more than 0.432 Hz does not have a liquefaction potential.