Banded microstructure
A striped, parallel alignment of microstructural phases caused by the alignment of element segregations during rolling. It leads to anisotropic mechanical properties.
Stringer structure forms when impurities like sulfur and oxides get stretched out during rolling. That gives you a structure with weak, streaky areas. If you then have stress perpendicular to the plate surface during welding, these streaks can tear open – that's the lamellar tear, which then breaks in a terrace-like pattern.
If you have components that are loaded in the through-thickness direction, use steel with Z-quality. These have significantly less sulfur and are specially tested for that. When welding itself: use low-hydrogen filler material, i.e., basic electrodes or flux-cored wire with low diffusible hydrogen. And you should plan the welding sequence so that shrinkage stress doesn't press perpendicular to the plate surface.
If you suspect heavy stringer structure, an ultrasonic test is worth it to find laminations in the plate.