Ground motion and stratum thickness comparison in Tower Hamlets, London

This report is the published product of a study by the British Geological Survey (BGS) to identify the impact of thickness and distribution of different strata beneath the borough of Tower Hamlets in London compared against temporal ground motion resulting from anthropogenic activities. Other units which are known to have potential high shrink and swelling characteristics in this location were also considered. Focus was on a newly developed Artificially Modified Ground (AMG) 3D layer where the thickness and distribution was calculated using boreholes and landuse types. The layer has been used to refine the thickness of the other lithological units in the area. Ground motion data for the 2015-2018 period was derived using spaceborne Interferometric Synthetic Aperture Radar (InSAR) which can measure surface displacement to millimetre accuracy in urban areas. A machine learning technique, called cluster analysis, has been used to group ground motion pattern of 23,245 points within the borough in space and time. The relationship with the thickness of the AMG and the underlying superficial and bedrock units was then studied. The results show that, within the area of study, the main component of motion is the uplift connected, in time, with the underground anthropogenic activities in the area. Ground displacement patterns are not connected with the thickness of the thickest and deepest units (London Clay, Lambeth Group and Thanet Formation) but have a connection to the most superficial deposits (Alluvium, River Terrace Deposits, Langley Silt Member and Kempton Park Gravel Member).