Mapping Deep Granite Bedrock in Eastern Singapore Using Passive Seismic Data

Abstract According to the existing geological model, the OA deposits in eastern Singapore have the potential to form a deep aquifer system bounded by the underlying Bukit Timah Granite. However, the depth to the Bukit Timah bedrock is highly uncertain due to the limited borehole information, resulting in uncertainty in the potential storage capacity estimation for groundwater injection. To estimate the depth of the bedrock beyond 100 m, this study uses the passive Surface-Wave Method (SWM) to map the underlying granite in the OA areas. The experiments utilize ambient noise vibrations in the urban area of Singapore as the noise source, and the noise direction is calibrated using active data induced by sledgehammering. Based on experiments conducted in six different sites on the eastern edge of Singapore, we update the geological model of eastern Singapore and provide a more accurate depth to bedrock for further aquifer estimation.