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Diagram illustrating the structural relationship between grabens and horsts. A downthrown block between two normal faults dipping towards each other is a graben. A block stranded between two grabens, and therefore two normal faults dipping away from each other, is a horst.
Anderson's theory of faulting. Anderson's theory of faulting, devised by Ernest Masson Anderson in 1905, is a way of classifying geological faults by use of principal stress. [1][2] A fault is a fracture in the surface of the Earth that occurs when rocks break under extreme stress. [3] Movement of rock along the fracture occurs in faults.
Horst and graben. In geology, horst and graben (or range and valley) refers to topography consisting of alternating raised and lowered fault blocks known as horsts and grabens. The features are created by normal faulting and rifting caused by crustal extension. [1] Horst and graben are formed when normal faults of opposite dip occur in pairs ...
Diagram of horsts and grabens. In physical geography and geology, a horst is a raised fault block bounded by normal faults. [1] Horsts are typically found together with grabens. While a horst is lifted or remains stationary, the grabens on either side subside. [2] This is often caused by extensional forces pulling apart the crust.
Reverse faults. A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. [ 1 ][ 2 ] If the angle of the fault plane is lower (often less than 15 degrees from the horizontal [ 3 ]) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an overthrust or overthrust fault. [ 4 ]
With crustal extension, a series of normal faults which occur in groups, form in close proximity and dipping in opposite directions. [4] As the crust extends it fractures in series of fault planes, some blocks sink down due to gravity, creating long linear valleys or basins also known as grabens, while the blocks remaining up or uplifted produce mountains or ranges, also known as horsts.
Fault plane solutions are useful for defining the style of faulting in seismogenic volumes at depth for which no surface expression of the fault plane exists or where an ocean covers the fault trace. A simple example of a successful test of the hypothesis of sea floor spreading was the demonstration that the sense of motion along oceanic ...
A pull-apart basin is a structural basin where two overlapping (en echelon) strike-slip faults or a fault bend create an area of crustal extension undergoing tension, which causes the basin to sink down. Frequently, the basins are rhombic or sigmoidal in shape. Dimensionally, basins are limited to the distance between the faults and the length ...