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 the megathrust faults of 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.
In geology, a shear zone is a thin zone within the Earth's crust or upper mantle that has been strongly deformed, due to the walls of rock on either side of the zone slipping past each other. In the upper crust, where rock is brittle, the shear zone takes the form of a fracture called a fault. In the lower crust and mantle, the extreme conditions of pressure and temperature make the rock ductile. That is, the rock is capable of slowly deforming without fracture, like hot metal being worked by a blacksmith. Here the shear zone is a wider zone, in which the ductile rock has slowly flowed to accommodate the relative motion of the rock walls on either side.
A cataclastic rock is a type of fault rock that has been wholly or partly formed by the progressive fracturing and comminution of existing rocks, a process known as cataclasis. Cataclasis involves the granulation, crushing, or milling of the original rock, then rigid-body rotation and translation of mineral grains or aggregates before lithification. Cataclastic rocks are associated with fault zones and impact event breccias.
The brittle-ductile transition zone is the zone of the Earth's crust that marks the transition from the upper, more brittle crust to the lower, more ductile crust. For quartz and feldspar-rich rocks in continental crust, the transition zone occurs at an approximate depth of 20 km, at temperatures of 250–400 °C. At this depth, rock becomes less likely to fracture, and more likely to deform ductilely by creep because the brittle strength of a material increases with confining pressure, while its ductile strength decreases with increasing temperature.
Pseudotachylyte is an extremely fine-grained to glassy, dark, cohesive rock occurring as veins that form through frictional melting and subsequent quenching during earthquakes, large-scale landslides, and impacts events. Chemical composition of pseudotachylyte generally reflects the local bulk chemistry, though may skew to slightly more mafic compositions due to the preferential incorporation of hydrous and ferro-magnesian minerals into the melt phase.
The Queen Charlotte Fault is an active transform fault that marks the boundary of the North American plate and the Pacific plate. It is Canada's right-lateral strike-slip equivalent to the San Andreas Fault to the south in California. The Queen Charlotte Fault forms a triple junction south with the Cascadia subduction zone and the Explorer Ridge. The Queen Charlotte Fault (QCF) forms a transpressional plate boundary, and is as active as other major transform fault systems in terms of slip rates and seismogenic potential. It sustains the highest known deformation rates among continental or continent-ocean transform systems globally, accommodating greater than 50mm/yr dextral offset. The entire approximately 900 km offshore length has ruptured in seven greater than magnitude 7 events during the last century, making the cumulative historical seismic moment release higher than any other modern transform plate boundary system.
In geology, a slickenside is a smoothly polished surface caused by frictional movement between rocks along a fault. This surface is typically striated with linear features, called slickenlines, in the direction of movement.
Mary Lou Zoback is an American geophysicist and seismologist. A specialist in tectonic stress and natural hazards risks, she spent most of her career as a research scientist with the United States Geological Survey. Zoback chaired the World Stress Map project of the International Lithosphere Program from 1986 to 1992. Zoback served on the U.S. Nuclear Waste Technical Review Board from 2012 to 2018.
Sharon Mosher is an American geologist. She did her undergraduate work at University of Illinois Urbana-Champaign. After earning an MSc from Brown University, she returned to the University of Illinois to get her PhD in Geology in 1978. Since 2001 she has held the William Stamps Farish Chair at University of Texas, and, since 2009 she has served as the dean of the Jackson School of Geosciences at Texas. In 2013 she became the president of the American Geosciences Institute.
Richard Hugh Sibson is a New Zealand structural geologist and emeritus professor at the University of Otago, who has received numerous honors and awards for his work in the field of earthquake research. He has caused a 'fundamental shift' in the interpretation of the relationship between earthquakes and fault zone geology and on the origin of fault-hosted mineral deposits.
Emily E. Brodsky is a Professor of Earth Sciences at the University of California, Santa Cruz. She studies the fundamental physical properties of earthquakes, as well as the seismology of volcanoes and landslides. In 2023, she was elected to the National Academy of Sciences.
Joan S. Gomberg is a research geophysicist at the United States Geological Survey. She serves as an adjunct professor at the University of Washington. She is interested in subduction zone science, and studies how earthquakes trigger each other and how faults can slip. Gomberg is a Fellow of the American Geophysical Union. She was the first person to demonstrate how dynamic stress associated with seismic waves can trigger other earthquakes.
The Canadian Arctic Rift System is a major North American geological structure extending from the Labrador Sea in the southeast through Davis Strait, Baffin Bay and the Arctic Archipelago in the northwest. It consists of a series of interconnected rifts that formed during the Paleozoic, Mesozoic and Cenozoic eras. Extensional stresses along the entire length of the rift system have resulted in a variety of tectonic features, including grabens, half-grabens, basins and faults.
This is a compilation of the properties of different analog materials used to simulate deformational processes in structural geology. Such experiments are often called analog or analogue models. The organization of this page follows the review of rock analog materials in structural geology and tectonics of Reber et al. 2020.
Whitney Maria Behr is an American earth scientist known for her contributions to understanding mechanics and kinematics of deformation in Earth's lithosphere. She was educated in the United States following which she held academic positions there. Since 2018, she has been the chair of the Structural Geology & Tectonics Group in the Geological Institute at ETH Zürich.
Julia Ann “Jan” Tullis is an American structural geologist and emerita Professor at Brown University. Tullis is known for her work in structural geology, especially for her experimental work in deformation mechanisms, microstructures, and rheology of crustal rocks.
Anne Meltzer is a seismologist known for her research on earthquakes and the formation of mountain ranges. Her research primarily focused on the evolution of the Earth's lithosphere and the surface processes associated with faulting and deformation in the Earth's crust. Through her own personal research and collaboration with other colleagues, she strived to make advancements in the efficiency and effectiveness of monitoring earthquakes. In addition, her work aimed to effectively reduce earthquake destruction in countries that experience frequent seismic phenomena.
Ruth Harris is a scientist at the United States Geological Survey known for her research on large earthquakes, especially on how they begin, end, and cause the ground to shake. In 2019, Harris was elected a fellow of the American Geophysical Union who cited her "for outstanding contributions to earthquake rupture dynamics, stress transfer, and triggering".
Elizabeth Scott Cochran is a seismologist known for her work on early warning systems for earthquakes and human-induced earthquakes.
Richard Waldron Allmendinger is a structural geologist and Professor Emeritus of Earth and Atmospheric Sciences at Cornell University.
