Seeing fault relays in outcrop is a great reminder that analysing structures in 2D is rarely good enough! In the real world, segmentation of a 3D rock volume by fault relays radically changes fluid migration paths, and can have critical implications for seismic hazard. Lots of structural geologists have worked on fault relays – though few come close to matching the fantastic legacy of the Fault Analysis Group in Dublin!
Main image (above): Small-scale fault relays in Carboniferous limestone-shale sequence, Lamberton, SE Scotland.
Satellite image of fault relays in Canyonlands, Utah, USA. Area of image is 3.4 x 5.8 km.
We’ve studied the distribution of strain in relay zones and the interplay between fault displacement and folding at relay tips for years, but there’s plenty of research still to be done. All of which seems like a good opportunity to mention again some really interesting work on relays by Alex Lăpădat. It’s 12 months since this first appeared online, so the embargo period has now passed, and if you haven’t already seen the paper, a pre-print is now freely available here. There’s more work on relays in the pipeline from Alex, so watch this space!