Estimation of S-wave Velocity Structure for Sedimentary Layered Media Using Microtremor Array Measurements in Palu City, Indonesia

AbstractIn this study, 8 array microtremor measurements have performed in Palu City, Indonesia for S-wave velocity profiles, which will be used in seismic hazard mapping. Four accelerometers were used in each array observation site. One was installed at a center of the circle with a radius, r. Other three were arranged on the circle with a shape of regular triangle. Sequential observations were conducted three times by changing the array radius; r=3, 10 and 30 meters. The ground profile was estimated by means of the dispersion curves obtained using the Spatial Autocorrelation (SPAC) methods. The Particle Swarm Optimization (PSO) technique was introduced to determine the dispersion curves. Unified two-layered model were reconstructed by averaging the first three layers obtained from array observation. The shear wave velocity of the top layer is Vs≤ 300 m/s. Based on layer models identified, sedimentary layer was estimated around Palu City.Understanding the parameters of sedimentary layersis important for seismic hazard mitigation and environmental planning in Paul City