The near-surface of London is faulted; however, their locations, architecture and tectonic origins are broadly unknown. This presents serious issues for geotechnical engineering in London and has implications for our structural understanding of the London Basin.
The region is a product of Alpine compression, yet it is unclear if these major faults were new Alpine shears or reactivated basement faults. Here the plausibility of Alpine reactivation and inheritance of basement faults in London is assessed through three investigations: analysing structures in the near-surface; mechanically assessing the feasibility of basement fault reactivation under Alpine stress conditions; and comparing inheritance mechanisms with observations in London and the Thames Estuary.
Three major en échelon fault sets have been identified. These appear to have compartmentalised London's near-surface geology and are interpreted to all be products of Alpine reactivation of underlying basement faults. Fault interaction and linkage is evidenced by complex zones of intense faulting identified by tunnelling projects. The role of new structure development in accommodating Alpine compression is considered to have been comparatively minor.
The lack of major faulting in the Basin's interior may reflect the competence of the underlying Anglo-Brabant Massif in restricting Alpine strains to its margins.
Thematic collection: This article is part of the Geology of London and its implications for ground engineering collection available at: https://www.lyellcollection.org/cc/london-basin