Systems and methods provide for the reduction of motion at a ground layer of a site due to a seismic event. A predicted seismic motion is obtained for a geological layer at depth and properties of the layers between the ground layer and layer at depth are determined. A model is created using the layers and the predicted seismic motion. Iteratively for each layer, one or more properties of the layer is changed in the model and a site amplification is performed to determine a change or changes that result in an acceptable response at the ground layer. Subsequently, the in situ layer may be modified according to the modified property or properties to reduce motion at the site due to a seismic event.