Optimized passive seismic interferometry for bedrock detection: A Singapore case study

We present a case study of passive seismic interferometry in the city of Singapore to investigate the bedrock depth and to determine the optimal acquisition parameters. The ambient-noise field, dominated by urban traffic noise, is recorded passively for seismic interferometry. We demonstrate that the bedrock depth can be determined from ambient seismic noise within an error of 2 m compared with borehole logs. Both synthetic and field data analysis show that the optimal array size for the passive site investigation can be as short as 30 m with 6 vertical geophones, to resolve a 1-D shear wave velocity profile of 50m in depth. Convergence of the cross-correlograms shows that the minimum acquisition time for ambient-noise acquisition is about 15 mins in a typical working day. Success of this case study demonstrates that accurate nearsurface site investigation can be achieved with faster acquisition, fewer receivers and smaller acquisition footprint, all of which improve the efficiency particularly in a highly developed urban environment.