In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes. Faults may also displace slowly, by aseismic creep.
The Great Glen Fault is a long strike-slip fault that runs through its namesake, the Great Glen, in Scotland. The fault is mostly inactive today, but occasional moderate tremors have been recorded over the past 150 years.
The Highland Boundary Fault is a major fault zone that traverses Scotland from Arran and Helensburgh on the west coast to Stonehaven in the east. It separates two different geological terranes which give rise to two distinct physiographic terrains: the Highlands and the Lowlands, and in most places it is recognisable as a change in topography. Where rivers cross the fault, they often pass through gorges, and the associated waterfalls can be a barrier to salmon migration.
In geology, shear is the response of a rock to deformation usually by compressive stress and forms particular textures. Shear can be homogeneous or non-homogeneous, and may be pure shear or simple shear. Study of geological shear is related to the study of structural geology, rock microstructure or rock texture and fault mechanics.
Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body's crust or lithosphere.
In geology, transpression is a type of strike-slip deformation that deviates from simple shear because of a simultaneous component of shortening perpendicular to the fault plane. This movement ends up resulting in oblique shear. It is generally very unlikely that a deforming body will experience "pure" shortening or "pure" strike-slip. The relative amounts of shortening and strike-slip can be expressed in the convergence angle alpha which ranges from zero to 90 degrees. During shortening, unless material is lost, transpression produces vertical thickening in the crust. Transpression that occurs on a regional scale along plate boundaries is characterized by oblique convergence. More locally, transpression occurs within restraining bends in strike-slip fault zones.
Strike-slip tectonics is concerned with the structures formed by, and the tectonic processes associated with, zones of lateral displacement within the Earth's crust or lithosphere. It is one of the three main types of tectonic regime, the others being extensional tectonics and thrust tectonics. These match the three types of plate boundary: transform (strike-slip), divergent (extensional) and convergent (thrust). Areas of strike-slip tectonics are associated with particular deformation styles including Riedel shears, flower structures and strike-slip duplexes. This type of tectonics is characteristic of several geological environments, including oceanic and continental transform faults, zones of oblique collision and the deforming foreland of a zone of continental collision.
The Orcadian Basin is a sedimentary basin of Devonian age that formed mainly as a result of extensional tectonics in northeastern Scotland after the end of the Caledonian orogeny. During part of its history, the basin was filled by a lake now known as Lake Orcadie. In that lacustrine environment, a sequence of finely bedded sedimentary rocks was deposited, containing well-preserved fish fossils, with alternating layers of mudstone and coarse siltstone to very fine sandstone. These flagstones split easily along the bedding and have been used as building material for thousands of years. The deposits of the Orcadian Basin form part of the Old Red Sandstone (ORS). The lithostratigraphic terms lower, middle and upper ORS, however, do not necessarily match exactly with sediments of lower, middle and upper Devonian age, as the base of the ORS is now known to be in the Silurian and the top in the Carboniferous.
The Southern Uplands Fault is a fault in Scotland that runs from Girvan to Dunbar on the East coast. It marks the southern boundary of the Scottish Midland Valley and the northern margin of the Southern Uplands; indeed it is recognised as a boundary between these two terranes. Both sinistral and dextral strike-slip movement is recorded from parts of the fault as are down-north and down-south normal movements suggestive of a complex history.
The 1911 Kebin earthquake, or Chon-Kemin earthquake, struck Russian Turkestan on 3 January. Registering at a 7.7 magnitude, it killed 452 people, destroyed more than 770 buildings in Almaty, Kazakhstan, and resulted in 125 miles (201 km) of surface faulting in the valleys of Chon-Kemin, Chilik and Chon-Aksu.
The Altyn Tagh Fault (ATF) is a 2,000 km long, active, sinistral strike-slip fault that forms the northwestern boundary of the Tibetan Plateau with the Tarim Basin. It is one of the major sinistral strike-slip structures that together help to accommodate the eastward motion of this zone of thickened crust, relative to the Eurasian Plate. A total displacement of about ~475 km has been estimated for this fault zone since the middle Oligocene, although the amount of displacement, age of initiation and slip rate are disputed.
The 1932 Ierissos earthquake occurred at 19:20 on 26 September. It caused severe damage in Ierissos and the surrounding part of the Chalkidiki peninsula, with 161–491 casualties reported.
The Aber Dinlle Fault is a SW-NE trending fault in North Wales. It forms part of the Menai Strait Fault System, with the Berw and Dinorwic Faults. It lies close to the epicentre of the 1984 Llŷn Peninsula earthquake, although it is not thought to have been responsible for that event. The fault was active during deposition of Ordovician rocks in the Welsh Basin. It was reactivated as a normal fault in the Carboniferous with a downthrow to the northwest and again reactivated as a reverse fault during Late Carboniferous inversion associated with the Variscan Orogeny.
The Cwm Llwyd Fault is a fault in the west of the Black Mountain of South Wales. It runs north, parallel to the A4069 road, for over 4 km from near Brynaman to meet the Carreg Cennen Disturbance near Brest Cwm Llwyd. It moved as a sinistral strike-slip fault during the Variscan Orogeny. Together with the Llwyn Celyn Fault it formed a left-stepping offset that created a pull apart structure, which preserved the Cwm Llwyd Outlier of Namurian rocks.
The Atacama Fault Zone (AFZ) is an extensive system of faults cutting across the Chilean Coastal Cordillera in Northern Chile between the Andean Mountain range and the Pacific Ocean. The fault system is North-South striking and runs for more than 1100 km North and up to 50 km in width through the Andean forearc region. The zone is a direct result of the ongoing subduction of the Eastward moving Nazca Plate beneath the South American Plate and is believed to have formed in the Early Jurassic during the beginnings of the Andean orogeny. The zone can be split into 3 regions: the North, Central and South.
The Sobral fault is a major fault in the Borborema geological province of northeastern Brazil, a part of the Transbrasiliano lineament. It is commonly correlated with the Kandi fault in Benin, east of the West African craton. The fault lies in the northwest of Ceará state. It appears to have formed late in the orogeny when the West African craton engaged with the Congo craton, and to have allowed significant dextral strike-slip movement. It was reactivated when South America was breaking away from Africa. In this later phase, a sinistral shear movement of about 100 km seems to have taken place during and after the break-up.
The Red River Fault or Song Hong Fault is a major fault in Yunnan, China and Vietnam which accommodates continental China's southward movement It is coupled with that of the Sagaing Fault in Burma, which accommodates the Indian plate's northward movement, with the land (Indochina) in between faulted and twisted clockwise. It was responsible for the 1970 Tonghai earthquake.
The Bangong suture zone is approximately 1200 km long and trends in an east–west orientation, and a key location in the central Tibet conjugate fault zone. Located in central Tibet between the Lhasa and Qiangtang terranes, it is a discontinuous belt of ophiolites and mélange that is 10–20 km wide, up to 50 km wide in places. The northern part of the fault zone consists of northeast striking sinistral strike-slip faults while the southern part consists of northwest striking right lateral strike-slip faults. These conjugate faults to the north and south of the Bangong intersect with each other along the Bangong-Nujiang suture zone.
The El Tigre Fault is a 120 km long, roughly north-south trending, major strike-slip fault located in the Western Precordillera in Argentina. The Precordillera lies just to the east of the Andes mountain range in South America. The northern boundary of the fault is the Jáchal River and its southern boundary is the San Juan River. The fault is divided into three sections based on fault trace geometry, Northern extending between 41–46 km in length, Central extending between 48–53 km in length, and Southern extending 26 km in length. The fault displays a right-lateral (horizontal) motion and has formed in response to stresses from the Nazca Plate subducting under the South American Plate. It is a major fault with crustal significance. The Andes Mountain belt trends with respect to the Nazca Plate/South American Plate convergence zone, and deformation is divided between the Precordilleran thrust faults and the El Tigre strike-slip motion. The El Tigre Fault is currently seismically active.
The Zhongwei-Tongxin fault or Tianjingshan fault is an arcuate sinistral (left-lateral) strike-slip zone, forming one of the major structures on the northeastern margin of Tibetan plateau. Six paleoearthquake events in the past 14,000 years have been recorded along the Zhongwei-Tongxin fault zone. Among the earthquakes recorded are the 1622 North Guyuan earthquake, which had a magnitude of 7.0 and mid-seismogenic depth of about 15 kilometres (9.3 mi), the 1709 Zhongwei earthquake, which had a magnitude of 7.5.
