"Canadian shield. POLARIS (seismology) POLARIS was an underground experiment to observe seismic signals at depth in very hard rock. It was carried out at SNOLAB, and underground physics laboratory, in Sudbury, Ontario. In addition to academic research, the data generated in the POLARIS experiment was used by the Canadian National Data Centre (CNDC) for earthquake, and nuclear explosion (see Partial Nuclear Test Ban Treaty) monitoring. SNOlab is an underground physics lab situated deep in the Creighton Mine, a 2 km deep Nickel mine operated by the Vale Limited. The mine is situated in the Sudbury Basin: a large impact crater"
"Seismicity Seismicity is a measure which encompasses earthquake occurrences, mechanisms, and magnitude at a given geographical location. As such it summarizes a region's seismic activity. The term was coined by Beno Gutenberg and Charles Francis Richter in 1941. Seismicity is studied by geophysicists. Seismicity is quantitatively computed. Generally the region under study is divided in equally sized areas defined by latitude and longitude and the interior of the Earth is divided into various depth intervals on account of Earth's layering: Up to 50 km depth, 50–300 km, and > 300 km. The usual formula to calculate seismicity is: formula_1 where"
"Seismicity Seismicity is a measure which encompasses earthquake occurrences, mechanisms, and magnitude at a given geographical location. As such it summarizes a region's seismic activity. The term was coined by Beno Gutenberg and Charles Francis Richter in 1941. Seismicity is studied by geophysicists. Seismicity is quantitatively computed. Generally the region under study is divided in equally sized areas defined by latitude and longitude and the interior of the Earth is divided into various depth intervals on account of Earth's layering: Up to 50 km depth, 50–300 km, and > 300 km. The usual formula to calculate seismicity is: formula_1 where"
"Forensic seismology Forensic seismology is the forensic use of the techniques of seismology to detect and study distant phenomena, particularly explosions, including those of nuclear weapons. Because of the efficiency with which seismic waves propagate through the Earth and the technical difficulties of decoupling explosions to diminish their seismic radiation, forensic seismology is a critical technique in the enforcement of bans on underground nuclear testing. In addition to nuclear explosions, the signatures of many other kinds of explosions can also be detected and analyzed by forensic seismology, and even other phenomena such as ocean waves (the global microseism), the movement"
"deformation of the crust and mantle from the scale of individual mineral grains up to that of tectonic plates. Seismotectonics is the study of the relationship between earthquakes, active tectonics, and individual faults in a region. It seeks to understand which faults are responsible for seismic activity in an area by analysing a combination of regional tectonics, recent instrumentally recorded events, accounts of historical earthquakes, and geomorphological evidence. This information can then be used to quantify the seismic hazard of an area. Techniques used in the analysis of tectonics on Earth have also been applied to the study of the"
"Seismic analysis Seismic analysis is a subset of structural analysis and is the calculation of the response of a building (or nonbuilding) structure to earthquakes. It is part of the process of structural design, earthquake engineering or structural assessment and retrofit (see structural engineering) in regions where earthquakes are prevalent. As seen in the figure, a building has the potential to 'wave' back and forth during an earthquake (or even a severe wind storm). This is called the 'fundamental mode', and is the lowest frequency of building response. Most buildings, however, have higher modes of response, which are uniquely activated"
"Seismotectonics Seismotectonics is the study of the relationship between the earthquakes, active tectonics and individual faults of a region. It seeks to understand which faults are responsible for seismic activity in an area by analysing a combination of regional tectonics, recent instrumentally recorded events, accounts of historical earthquakes and geomorphological evidence. This information can then be used to quantify the seismic hazard of an area. A seismotectonic analysis of an area often involves the integration of disparate datasets. An understanding of the regional tectonics of an area is likely to be derived from published geological maps, research publications on the"
"Lunar seismology Lunar seismology is the study of ground motions of the moon and the events, typically impacts or moonquakes, that excite them. Several seismographic measuring systems have already been installed on the moon and their data made available to scientists (such as those from the Apollo Lunar Surface Experiments Package). The existence of moonquakes was an unexpected discovery from seismometers placed on the Moon by Apollo astronauts from 1969 through 1972. The instruments placed by the Apollo 12, 14, 15 and 16 missions were functional until they were switched off in 1977. Moonquakes are not believed to be caused"
"Asteroseismology Asteroseismology or astroseismology is the study of oscillations in stars. Because a star's different oscillation modes are sensitive to different parts of the star, they inform astronomers about the internal structure of the star, which is otherwise not directly possible from overall properties like brightness and surface temperature. Asteroseismology is closely related to helioseismology, the study of stellar oscillations specifically in the Sun. Though both are based on the same underlying physics, more and qualitatively different information is available for the Sun because its surface can be resolved. By linearly perturbing the equations defining the mechanical equilibrium of a"
"that sound from E&P seismic activities has resulted in any physical or auditory injury to any marine mammal species."" The following books cover important topics in reflection seismology. Most require some knowledge of mathematics, geology, and/or physics at the university level or above. Further research in reflection seismology may be found particularly in books and journals of the Society of Exploration Geophysicists, the American Geophysical Union, and the European Association of Geoscientists and Engineers. <br> Reflection seismology Reflection seismology (or seismic reflection) is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the"
"Coronal seismology Coronal seismology is a technique of studying the plasma of the Sun's corona with the use of magnetohydrodynamic (MHD) waves and oscillations. Magnetohydrodynamics studies the dynamics of electrically conducting fluids - in this case the fluid is the coronal plasma. Observed properties of the waves (e.g. period, wavelength, amplitude, temporal and spatial signatures (what is the shape of the wave perturbation?), characteristic scenarios of the wave evolution (is the wave damped?), combined with a theoretical modelling of the wave phenomena (dispersion relations, evolutionary equations, etc.), may reflect physical parameters of the corona which are not accessible ""in situ,"""
"exploration. Seismic waves propagate and interact with subterranean components and respond accordingly. Two sub categories exist that are relevant to the source of the seismic signal. Active seismology relies on using induced/man-made vibrations at or near the surface. Passive seismology uses earthquakes, volcanic eruptions or other tectonic activity as sources. Passive seismic studies use natural wave propagation through the earth. Geothermal fields are often characterized by increased levels of seismicity. Earthquakes of lesser magnitude are much more frequent than ones of larger magnitude. Therefore, these micro earthquakes (MEQ), registering below 2.0 magnitude on the Richter scale, are used to reveal"
"interactions involving the atmosphere, ocean circulation, planetary volcanism, the cryosphere, the biosphere and external forces such as variability of solar radiation and even the occasional asteroid impact. Scientists are also increasingly interested in understanding the nature of past and present changes to Earth’s climate—whether abrupt or gradual, regional or global—and the potential for human activities to influence the natural system. The researchers in the Seismology, Geology and Tectonophysics Division (SGT) study theoretical and observational seismology, solid Earth dynamics, rock mechanics, structural geology and tectonics, and sedimentary geology. They also contribute to understanding of earthquakes; the structure of Earth’s crust, mantle,"
"Seismic tomography Seismic tomography is a technique for imaging the subsurface of the Earth with seismic waves produced by earthquakes or explosions. P-, S-, and surface waves can be used for tomographic models of different resolutions based on seismic wavelength, wave source distance, and the seismograph array coverage. The data received at seismometers are used to solve an inverse problem, wherein the locations of reflection and refraction of the wave paths are determined. This solution can be used to create 3D images of velocity anomalies which may be interpreted as structural, thermal, or compositional variations. Geoscientists use these images to"
"Speleology Speleology is the scientific study of caves and other karst features, their make-up, structure, physical properties, history, life forms, and the processes by which they form (speleogenesis) and change over time (speleomorphology). The term ""speleology"" is also sometimes applied to the recreational activity of exploring caves, but this is more properly known as ""caving"" or ""potholing"", or (not usually by participants) by the uncommon American term ""spelunking"". Speleology and caving are often connected, as the physical skills required for ""in situ"" study are the same. Speleology is a cross-disciplinary field that combines the knowledge of chemistry, biology, geology, physics,"
"Helioseismology Helioseismology, a term coined by Douglas Gough, is the study of the structure and dynamics of the Sun through its oscillations. These are principally caused by sound waves that are continuously driven and damped by convection near the Sun's surface. It is similar to geoseismology, or asteroseismology (also coined by Gough), which are respectively the studies of the Earth or stars through their oscillations. While the Sun's oscillations were first detected in the early 1960s, it was only in the mid-1970s that it was realised that the oscillations propagated throughout the Sun and could allow scientists to study the"
"geology, oil exploration, hydrology, and earthquake engineering, and structural health monitoring. It is often called ambient wavefield or ambient vibrations in those disciplines. (However, the latter term may also refer to vibrations transmitted through by air, building, or supporting structures.) Seismic noise is a nuisance for activities that are sensitive to vibrations, such as accurate measurements, precision milling, telescopes, and crystal growing. On the other hand, seismic noise does have some practical uses, for example to determine the low-strain dynamic properties of civil-engineering structures, such as bridges, buildings, and dams; or to determine the elastic properties of the soil and"
"Sedimentology Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation (erosion and weathering), transport, deposition and diagenesis. Sedimentologists apply their understanding of modern processes to interpret geologic history through observations of sedimentary rocks and sedimentary structures. Sedimentary rocks cover up to 75% of the Earth's surface, record much of the Earth's history, and harbor the fossil record. Sedimentology is closely linked to stratigraphy, the study of the physical and temporal relationships between rock layers or strata. The premise that the processes affecting the earth today are the same"
"study of the behavior of structures and geo-structures subject to seismic loading; it is considered as a subset of structural engineering, geotechnical engineering, mechanical engineering, chemical engineering, applied physics, etc. However, the tremendous costs experienced in recent earthquakes have led to an expansion of its scope to encompass disciplines from the wider field of civil engineering, mechanical engineering and from the social sciences, especially sociology, political science, economics and finance. The main objectives of earthquake engineering are: A properly engineered structure does not necessarily have to be extremely strong or expensive. It has to be properly designed to withstand the"
"collection and measurement of seismic waves or vibrations in the earth surface."" In the context of verification, seismic intelligence makes use of the science of seismology to locate and characterize nuclear testing, especially underground testing. Seismic sensors also can characterize large conventional explosions that are used in testing the high-explosive components of nuclear weapons. In 1960, George Kistiakowsky introduced the ""threshold principle"" that balances the needs of arms control with the realities of seismic verification. He cited the difficulty in monitoring missile submarines, and proposed that the arms control strategy focus on disarmament rather than inspections into verification, which accepts"
"Seismic noise In geology and other related disciplines, seismic noise is a generic name for a relatively persistent vibration of the ground, due to a multitude of causes, that is a non-interpretable or unwanted component of signals recorded by seismometers. Physically, seismic noise consists mostly of surface waves. Low frequency waves (below 1 Hz) are generally called microseisms; high frequency waves (above 1 Hz) are called microtremors. Its causes include nearby human activities (such as traffic or heavy machinery), winds and other atmospheric phenomena, and ocean waves. Seismic noise is relevant to any discipline that depends on seismology, such as"
"rock layers. Trenching studies are especially relevant to seismically active regions, such as many parts of California. Paleoseismology Paleoseismology looks at geologic sediments and rocks, for signs of ancient earthquakes. It is used to supplement seismic monitoring, for the calculation of seismic hazard. Paleoseismology is usually restricted to geologic regimes that have undergone continuous sediment creation for the last few thousand years, such as swamps, lakes, river beds and shorelines. In this typical example, a trench is dug in an active sedimentation regime. Evidence of thrust faulting can be seen in the walls of the trench. It becomes a matter"
"Earth's physical environment and developing a clearer picture of its sensitivities to natural and human-caused change. One chief area of study is the greenhouse effect and how to determine the onset of a theoretically predicted warming. Solid Earth Sciences Division (SES) Active research areas in geophysics include earthquake prediction; studies of the size, shape, and dynamic forces of Earth; isotope geochemistry; and the behavior of Earth’s core and mantle. This research involves the use of seismography, analytical and numerical modeling efforts, and space geodetic techniques, such as laser ranging, artificial satellites, and interferometric observations of radio waves emanating from deep"
"A region of higher electrical conductivity may have water or galena. For a good interpretation the geophysics model must be combined with geological knowledge of the area. Seismology makes use of the ability of vibrations to travel through rock as seismic waves. These waves come in two types: pressure waves (P-waves) and shear waves (S-waves). P-waves travel faster than S-waves, and both have trajectories that bend as the wave speeds change with depth. Refraction seismology makes use of these curved trajectories. In addition, if there are discontinuities between layers in the rock or sediment, seismic waves are reflected. Reflection seismology"
"on the cooling of the atmosphere following the eruption. Impacts from large celestial bodies, commonly asteroids, create shock waves that push air and distribute dust into the atmosphere, blocking sunlight. This causes global cooling, which can lead to the death and possible extinction of many species. Industrial applications of geophysics were developed by demand of petroleum exploration and recovery in the 1920s. Later, petroleum, mining and groundwater geophysics were improved. Earthquake hazard minimization and soil/site investigations for earthquake-prone areas were new applications of geophysical engineering in the 1990s. Seismology is used in the mining industry to read and build models"
"Seismometer A seismometer is an instrument that measures ground motions, such as caused by earthquakes, volcanic eruptions, and explosions. Records of seismic waves (seismograms) allow seismologists to locate and measure the size of events like these, and to map the Earth's internal structure. A simple seismometer, sensitive to up-down motions of the Earth, is like a weight hanging from a spring, both suspended from a frame that moves along with any motion detected. The relative motion between the weight (called the mass) and the frame provides a measurement of the vertical ground motion. A rotating drum is attached to the"
"Seismic wave Seismic waves are waves of energy that travel through the Earth's layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions that give out low-frequency acoustic energy. Many other natural and anthropogenic sources create low-amplitude waves commonly referred to as ambient vibrations. Seismic waves are studied by geophysicists called seismologists. Seismic wave fields are recorded by a seismometer, hydrophone (in water), or accelerometer. The propagation velocity of the waves depends on density and elasticity of the medium.Velocity tends to increase with depth and ranges from approximately 2 to 8 km/s in"
"Seismite Seismites are sedimentary beds and structures deformed by seismic shaking. The German paleontologist Adolf Seilacher first used the term in 1969 to describe earthquake-deformed layers. Today, the term is applied to both sedimentary ""layers"" and soft sediment deformation ""structures"" formed by shaking. This subtle change in usage accommodates structures that may not remain within a layer (i.e., clastic dikes or sand volcanos). Caution is urged when applying the term to features observed in the field, as similar-looking features may be products of either seismic or non-seismic perturbation. Several informal classification systems exist to help geologists distinguish seismites from other"
"interior of structures, where the stress and strain level is important for the overall structural integrity. Since the sound velocity of such non-linear elastic materials (including common construction materials like aluminium and steel) have a stress dependency, one application of the acoustoelastic effect may be measurement of the stress state in the interior of a loaded material utilizing different acoustic probes (e.g. ultrasonic testing) to measure the change in sound velocities. seismology study the propagation of elastic waves through the Earth and is used in e.g. earthquake studies and in mapping the Earth's interior. The interior of the Earth is"
"based on visual perceptions of color, such as the change from orange to red being more subtle than blue to yellow. The degree of color saturation can also visually skew interpretations. These factors should be considered when analyzing images. Seismic tomography Seismic tomography is a technique for imaging the subsurface of the Earth with seismic waves produced by earthquakes or explosions. P-, S-, and surface waves can be used for tomographic models of different resolutions based on seismic wavelength, wave source distance, and the seismograph array coverage. The data received at seismometers are used to solve an inverse problem, wherein"
"Reflection seismology Reflection seismology (or seismic reflection) is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite or Tovex blast, a specialized air gun or a seismic vibrator, commonly known by the trademark name Vibroseis. Reflection seismology is similar to sonar and echolocation. This article is about surface seismic surveys; for vertical seismic profiles, see VSP. Reflections and refractions of seismic waves at geologic interfaces within the Earth were first observed on recordings of"
"Geology Geology (from the Ancient Greek γῆ, ""gē""(""earth"") and -λoγία, ""-logia"", (""study of"", ""discourse"")) is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also refer to the study of the solid features of any terrestrial planet or natural satellite such as Mars or the Moon. Modern geology significantly overlaps all other earth sciences, including hydrology and the atmospheric sciences, and so is treated as one major aspect of integrated earth system science and planetary science. Geology describes the structure of the Earth"
"seismology and allied disciplines. The major activities currently being pursued by the National Center for Seismology include, a) earthquake monitoring on 24X7 basis, including real time seismic monitoring for early warning of tsunamis, b) Operation and maintenance of national seismological network and local networks c) Seismological data centre and information services, d) Seismic hazard and risk related studies e) Field studies for aftershock / swarm monitoring, site response studies f) earthquake processes and modelling, etc. The MSK (Medvedev-Sponheuer-Karnik) intensity broadly associated with the various seismic zones is VI (or less), VII, VIII and IX (and above) for Zones 2, 3,"