 | The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject.(April 2020) |
A sag pond is a body of fresh water [1] collected in the lowest parts of a depression formed between two sides of an active strike-slip, transtensional or normal fault zone. [2] [3]
A sag pond is formed along a strike-slip fault, which may create a depression in the earth. [4] [5] When water enters the depression from rivers, streams, rainfall or snowfall, it fills the low-lying area, and a pond is the result. [6]
Sag pond formation is common in California, [7] and many of them can be found on the San Andreas Fault, which runs through the western part of the state. [8] [9] Aerial photography or high-resolution topography can easily determine their locations. [10]
Sag ponds have been converted into stock reservoirs. [11] Larger sag ponds are converted into reservoirs for public water sources, such as San Andreas Lake [12]
Sag ponds of various sizes can be found along the San Andreas Fault, most notably within the Carrizo Plain and Sierra Pelona Mountains. Some have been converted into reservoirs like the San Andreas Reservoir near San Bruno, California. Various lagoons on the plateau of Pico Island in the Azores are the result of a graben. [13]
Sedimentary basins are regions of the Earth where long-term subsidence creates accommodation space for accumulation of sediments. As the sediments are buried, they are subject to increasing pressure and begin the processes of compaction and lithification that transform them into sedimentary rock.
The Los Angeles Basin is a sedimentary basin located in southern California, in a region known as the Peninsular Ranges. The basin is also connected to an anomalous group of east-west trending chains of mountains collectively known as the Transverse Ranges. The present basin is a coastal lowland area, whose floor is marked by elongate low ridges and groups of hills that is located on the edge of the Pacific Plate. The Los Angeles Basin, along with the Santa Barbara Channel, the Ventura Basin, the San Fernando Valley, and the San Gabriel Basin, lies within the greater southern California region. On the north, northeast, and east, the lowland basin is bound by the Santa Monica Mountains and Puente, Elysian, and Repetto hills. To the southeast, the basin is bordered by the Santa Ana Mountains and the San Joaquin Hills. The western boundary of the basin is marked by the Continental Borderland and is part of the onshore portion. The California borderland is characterized by northwest trending offshore ridges and basins. The Los Angeles Basin is notable for its great structural relief and complexity in relation to its geologic youth and small size for its prolific oil production. Yerkes et al. identify five major stages of the basin's evolution, which began in the Upper Cretaceous and ended in the Pleistocene. This basin can be classified as an irregular pull-apart basin accompanied by rotational tectonics during the post-early Miocene.
The 1857 Fort Tejon earthquake occurred at about 8:20 a.m. on January 9 in central and Southern California. One of the largest recorded earthquakes in the United States, with an estimated moment magnitude of 7.9, it ruptured the southern part of the San Andreas Fault for a length of about 225 miles, between Parkfield and Wrightwood.
In geology, aseismic creep or fault creep is measurable surface displacement along a fault in the absence of notable earthquakes. Aseismic creep may also occur as "after-slip" days to years after an earthquake. Notable examples of aseismic slip include faults in California.
In geology, a depression is a landform sunken or depressed below the surrounding area. Depressions form by various mechanisms.
The Newport–Inglewood Fault is a right-lateral strike-slip fault in Southern California. The fault extends for 47 mi (76 km) from Culver City southeast through Inglewood and other coastal communities to Newport Beach at which point the fault extends east-southeast into the Pacific Ocean where it is known as the Rose Canyon Fault. The fault can be inferred on the Earth's surface as passing along and through a line of hills extending from Signal Hill to Culver City. The fault has a slip rate of approximately 0.6 mm (0.024 in)/year and is predicted to be capable of a 6.0–7.4 magnitude earthquake on the moment magnitude scale. A 2017 study concluded that, together, the Newport–Inglewood Fault and Rose Canyon Fault could produce an earthquake of 7.3 or 7.4 magnitude.
The Elsinore Fault Zone is a large right-lateral strike-slip geological fault structure in Southern California. The fault is part of the trilateral split of the San Andreas fault system and is one of the largest, though quietest faults in Southern California.
Thrust tectonics or contractional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the shortening and thickening of the crust or lithosphere. It is one of the three main types of tectonic regime, the others being extensional tectonics and strike-slip tectonics. These match the three types of plate boundary, convergent (thrust), divergent (extensional) and transform (strike-slip). There are two main types of thrust tectonics, thin-skinned and thick-skinned, depending on whether or not basement rocks are involved in the deformation. The principle geological environments where thrust tectonics is observed are zones of continental collision, restraining bends on strike-slip faults and as part of detached fault systems on some passive margins.
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 Walker Lane is a geologic trough roughly aligned with the California/Nevada border southward to where Death Valley intersects the Garlock Fault, a major left lateral, or sinistral, strike-slip fault. The north-northwest end of the Walker Lane is between Pyramid Lake in Nevada and California's Lassen Peak where the Honey Lake Fault Zone, the Warm Springs Valley Fault, and the Pyramid Lake Fault Zone meet the transverse tectonic zone forming the southern boundary of the Modoc Plateau and Columbia Plateau provinces. The Walker Lane takes up 15 to 25 percent of the boundary motion between the Pacific Plate and the North American Plate, the other 75 percent being taken up by the San Andreas Fault system to the west. The Walker Lane may represent an incipient major transform fault zone which could replace the San Andreas as the plate boundary in the future.
The Athabasca Valles are a late Amazonian-period outflow channel system in the central Elysium Planitia region of Mars, located to the south of the Elysium Rise. They are part of a network of outflow channels in this region that are understood to emanate from large fissures in the Martian surface rather than the chaos terrains that source the circum-Chryse outflow channels. The Athabasca Valles in particular emanate from one of the Cerberus Fossae fissures and flow downstream to the southwest, constrained to the south by a wrinkle ridge for over 100 km, before debouching into the Cerberus Palus volcanic plain. The Athabasca Valles are widely understood to be the youngest outflow channel system on the planet.
In geology, a basin is a region where subsidence generates accommodation space for the deposition of sediments. A pull-apart basin is a structural basin where two overlapping strike-slip faults or a fault bend creates 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 of overlap. Pull-apart basins are also referred to as overlapping-tension-zones (OTZ).
The Ceraunius Fossae are a set of fractures in the northern Tharsis region of Mars. They lie directly south of the large volcano Alba Mons and consist of numerous parallel faults and tension cracks that deform the ancient highland crust. In places, younger lava flows cover the fractured terrain, dividing it into several large patches or islands. They are found in the Tharsis quadrangle.
Hughes Lake, referred to before 1924 as West Elizabeth Lake, is a lake on the San Andreas Fault in the northern Sierra Pelona Mountains, in Los Angeles County, California.
The Venezuelan Andes also simply known as the Andes in Venezuela, are a mountain system that form the northernmost extension of the Andes. They are fully identified, both by their geological origin as by the components of the relief, the constituent rocks and the geological structure.
Tectonic subsidence is the sinking of the Earth's crust on a large scale, relative to crustal-scale features or the geoid. The movement of crustal plates and accommodation spaces created by faulting create subsidence on a large scale in a variety of environments, including passive margins, aulacogens, fore-arc basins, foreland basins, intercontinental basins and pull-apart basins. Three mechanisms are common in the tectonic environments in which subsidence occurs: extension, cooling and loading.
In geology, a piercing point is defined as a feature that is cut by a fault, then moved apart. Reconfiguring the piercing point back in its original position is the primary way geologists can find out the minimum slip, or displacement, along a fault. This can be done on a large scale, a small scale or even a single hand sample/rock.
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 Rosas-Julumito Fault is an oblique dextral strike-slip fault in the department of Cauca in southwestern Colombia. The fault is part of the megaregional Romeral Fault System and has a total length of 43.3 kilometres (26.9 mi) and runs along an average northeast to southwest strike of 026.9 ± 7 in the Central Ranges of the Colombian Andes. The fault is associated with the 1983 Popayán earthquake that partially destroyed Popayán, the capital of Cauca, and led to more than 300 fatalities. A maximum moment magnitude earthquake of 6.8 is estimated for the fault.
The Mutatá Fault is a strike-slip fault in the department of Antioquia in northern Colombia. The fault has a total length of 44.7 kilometres (27.8 mi) and runs along an average northwest to southeast strike of 326.4 ± 11 in the Urabá Basin. The fault is active and produced the 2016 Mutatá earthquake with a moment magnitude of 6.0.
