Abstract

The Highland Boundary Fault (HBF) delineates a fundamental division in the topography and surface geology in Scotland, separating 1000- 500Ma metamorphic rocks to the north from predominantly ~440- 360Ma sedimentary rocks of the Midland Valley to the south. Despite detailed geological mapping of the HBF and surrounding areas, the role(s) of the HBF in the tectonic history of Scotland is contested.

To investigate crustal structure across the HBF and any seismicity in the region in spring 2022 we deployed a new network of 10 seismometers in north eastern Scotland as part of the PICTS (Probing Into the Crust Through eastern Scotland) project, which, together with a BGS Seismology permanent station, DRUM , form three transects across the HBF . These instruments form the first dense seismometer deployment in this region and data from them will allow us to place high-resolution constraints on the structure of the crust and uppermost mantle across the HBF , determine crustal thickness in this region, and to investigate if any seismicity is occurring on the eastern portion of the HBF . Preliminary results from crustal receiver functions indicate that the crystal structure is different to the north and the south of the HBF .