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graben A downthrown, linear, crustal block, bordered lengthways by normal faults. The upstanding blocks on either side may have been lowered by erosion. It is a structural feature, which may be of considerable length, caused by the relative lowering of a block between two faults or fault zones. The faults are commonly high-angle, normal faults which are parallel in their strike direction. Half-graben are bounded on only one side by one or more faults and are associated mainly with tilt-block tectonics. Graben with a regional extent and topographic expression can also be called rift valleys. Compare HORST.

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