In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch or trench. The plural form is variously given as graben or grabens.
A graben is the result of a block of land being downthrown producing a valley with a distinct scarp on each side. Graben often occur side-by-side with horsts. Horst and graben structures are indicative of tensional forces and crustal stretching.
Graben are produced from parallel normal faults, where the hanging wall is downthrown and the footwall is upthrown. The faults typically dip toward the center of the graben from both sides. Horsts are parallel blocks that remain between graben; the bounding faults of a horst typically dip away from the center line of the horst.
Single or multiple graben can produce a rift valley.(Wikipedia)