Tectonics, TectonophysicsOff-fault tip splay networks: A genetic and generic property of faults indicative of their long-term propagation

We use fault maps and fault propagation evidences available in the literature to examine geometrical relations between parent faults and off-fault splays. The population includes 47 worldwide crustal faults with lengths from millimetres to thousands of kilometres and of different slip modes. We show that fault splays form adjacent to any propagating fault tip, whereas they are absent at non-propagating fault ends. Independent of fault length, slip mode, context, etc., tip splay networks have a similar fan shape widening in direction of long-term propagation, a similar relative length and width (∼ 30 and ∼ 10% of parent fault length, respectively), and a similar range of mean angles to parent fault (10-20°). We infer that tip splay networks are a genetic and a generic property of faults indicative of their long-term propagation. Their generic geometrical properties suggest they result from generic off-fault stress distribution at propagating fault ends.