Using ambient noise tomography and MAPS for high resolution stratigraphic identification in Hangzhou urban area

Abstract

Near-surface (<200 m) stratigraphic identification is of scientific and engineering significance to urban sustainable development and expansion. Complex urbanized environments, however, limit the application of traditional active-source seismic surveys. Passive seismic surveys provide an alternative for investigating near-surface structures by utilizing abundant traffic noise. We presented a case study of fine-scale shear-wave velocity (Vs) structure imaging in the Hangzhou urban area (eastern China) and compared inversion results of ambient noise tomography and multichannel analysis of passive surface wave (MAPS). Noise data were recorded within one day by a dense seismic network (130 m × 120 m). The average adjacent station interval is about 10 m. Our goal is to investigate the top 100 m of the subsurface at the survey area. The two inverted Vs models by tomography and MAPS are similar and they both tally with the logging data. The subsurface geology structures are analyzed based on tomography inversion results and borehole data. The bedrock surface is determined at about 60 m depth and a high-velocity layer is found at around 45– 50 m depth. The sedimentary formation and bedrock in the survey area are further stratified under the control of borehole data.