Prof. John Walsh to deliver lecture at Geological Society of London.
Faults are components of systems which vary in complexity from what amounts to a single fault through to those which comprise many interacting faults.
Whatever their geometry, recent research indicates that fault interactions provide systems which often show very systematic growth patterns on geological timescales but become increasingly more complex on shorter timescales (e.g. thousands of years or less).
Details of the nature of fault system growth have been established from the analysis of high quality 3D outcrop or seismic datasets in circumstances where the history of faulting is preserved by the blanketing of contemporaneous sedimentary sequences. The behavioural complexity of fault movements which these studies reveal, highlights the importance of geological and palaeoseismological constraints in earthquake hazard and risk assessment.
Even the high sedimentation rates which promote the preservation of fault history have major implications for earthquake risking, with active faults potentially having no expression in the landscape and therefore going unrecognised.
Using case studies mainly from New Zealand, this talk considers some of the challenges associated with earthquake risking and reinforces the requirement for a combined geological and geophysical approach, even in tectonically active areas where faults have not previously been identified.