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Faults may also displace slowly, by aseismic creep. [2] A fault plane is the plane that represents the fracture surface of a fault. A fault trace or fault line is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geologic maps to represent a fault. [3] [4]
A detachment fault is a gently dipping normal fault associated with large-scale extensional tectonics. [1] Detachment faults often have very large displacements (tens of km) and juxtapose unmetamorphosed hanging walls against medium to high-grade metamorphic footwalls that are called metamorphic core complexes .
The geologic subdiscipline of stratigraphy is primarily concerned with depositional contacts, [4] while faults and shear zones are of particular interest in structural geology. Faults and shear zones can be regarded as a form of secondary structure in the rock beds.
Dip is defined as the angle of the fault relative to the surface of the earth, which indicates the plane on which slip will occur. Lastly, in any non-vertical fault, the block above the fault is called the hanging wall, while the blockbelow the fault is called the footwall. [4] Normal and reverse dip-slip faults with labeled hanging wall and ...
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]
A graben is a section of crust that has lowered relative to the blocks on either side, which is a result of its bounding faults dipping towards each other. [2] The plural of graben can be either graben or grabens. Graben form low-lying features such as basins and rift valleys. [1] [2] They can be very long relative to their width.
For a given stress state in the earth, if an existing fault or crack exists orientated anywhere from −α/4 to +α/4, this fault will slip before the strength of the rock is reached and a new fault is formed. While the applied stresses may be high enough to form a new fault, existing fracture planes will slip before fracture occurs.
An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,000 years. [1] Active faulting is considered to be a geologic hazard – one related to earthquakes as