Had no idea what seismic lines were so found this:
Seismic lines are straight or meandering pathways, 1.5 to 7 m wide and at least 2 km long, that are used in oil and gas exploration. Unlike roads, seismic lines are not maintained as clearings, however, they may fragment the landscape, carving open areas through formerly unbroken habitats. Such clearings may disturb species that deliberately avoid open edges and may increase their vulnerability to predators. Although seismic lines do not provide the level of human access associated with roads, they may create temporary routes for all-terrain vehicles and snow machines in winter.
Andrew