Spatial and temporal constraints on sources of seismic anisotropy: Evidence from the Scottish highlands

Routine SKS splitting analyses of seismic anisotropy usually suffer from limitations in station density that hinder attempts to place spatial constraints on anisotropic fabrics. Data from a ∼20 km station spacing network in Scotland show that splitting parameters vary considerably (δt = 0.45–1.5 s; ϕ = 49–128°) over short (10–20 km) length scales. Improved spatial constraints then lead to tighter temporal constraints on the anisotropic sources. Asthenospheric fabrics due to Tertiary rifting and present day plate motions do not strongly influence our results that instead correlate with lithospheric scale trends inferred from surface geology. Splitting observations track Scotland's tectonic history from the Precambrian emplacement of crustal basement and through the activation of large‐scale faulting and thrusting during the Caledonian Orogeny. The shallow lithosphere beneath Scotland has preserved a fossil anisotropic signature up to hundreds of millions of years after it was formed.