Brighton sits on a geological transition that complicates seismic response. The Cretaceous Chalk of the South Downs meets the London Clay Formation along the coastal plain, with a water table often within 3 metres of ground level. This sharp stiffness contrast amplifies ground motion at the boundary, a pattern documented in the British Geological Survey's 1:50,000 sheet for the district. Structures founded across these two materials require isolation systems that decouple the superstructure from differential foundation movement. Seismic microzonation helps map these velocity contrasts before selecting isolator parameters, and when chalk dissolution features are suspected, resistivity profiling identifies voiding that would undermine isolator performance.
An isolation system tuned to chalk will resonate on London Clay unless the substructure is stiff enough to force the isolators into their non-linear range early.
