Imaging shallow velocity structure using ambient noise in urban area

Vehicle traffic and other human activities provide affluent seismic excitation in urban area. We extract Green's function of surface wave from cross correlation of ambient noise recorded by a small array in schoolyard of Peking University. Although non-isotropic source distribution introduces bias in the Green's function reconstruction, relative steady phase and group velocity map could be estimated from only days' records. The inverted S structure demonstrates agreement with well logging data. This technique could be introduced to engineering for well location optimizing design in noisy urban environment.