HOMEActive fault: A fault along which slip has occurred, variously in historical, Holocene, or Quaternary time, or earthquake foci are located. Amplitude (wave): The maximum height of a wave crest or depth of a trough. Aseismic region: One that is almost free from earthquakes. Asperites (fault): Roughness on the fault surface subject to slip. Attenuation: The reduction in amplitude of a wave with time or distance traveled. Body wave: A seismic wave that travels through the interior of an elastic material. Body wave magnitude: The magnitude of an earthquake estimated from the amplitude of body waves. Core (of Earth): The central part of the Earth below a depth of 2900 kilometers. It is thought to be composed of iron and silicates and to be molten on the outside with a solid central part. Creep (Slow-fault slip): Slow slip occurring along the fault, without producing earthquakes. Crust (of Earth): The outermost rocky shell. Damping: Loss of energy in wave motion due to transfer into heat by frictional forces. Dip: The angle by which a rock layer or fault plane deviates from the horizontal. Earthquake: The vibrations of the Earth caused by the passage of seismic waves radiating from some source of elastic energy. Earthquake occurrence (recurrence) interval: The average time between the occurrences of earthquakes in a particular region. Epicenter: The point on the Earth’s surface directly above the focus (or hypocenter) of an earthquake Fault: A fracture or zone of fractures in rock along which the two sides have been displaced relative to each other parallel to the fracture. The total fault offset may range from centimeters to kilometers. Fault plane: The plane that most closely coincides with the rupture surface of a fault. Foreshocks: Smaller earthquakes preceding the largest earthquake of a series concentrated in a restricted crystal volume. Frequency: Number of oscillations per unit time; in Hertz (Hz) i.e., 1 cycle per second. Gouge: The crushed, sheared, and powdered rock altered to clay. Holocene: About 10,000 years before the present. Intensity (of earthquake): A measure of ground shaking obtained from the damage done to structures built by humans. Mantle (of Earth): The main bulk of the Earth, between the crust and core, ranging from depths of about 40 to 3470 kilometers. It is composed of dense silicate rocks and divided into a number of concentric shells. Microseism: Weak, almost continuos background seismic waves or Earth noise that can be detected only by seismographs often caused by surf, ocean waves, wind, or human activity. Origin time: The time of initiation of the seismic waves at earthquake source in U.T Period (of wave): The time interval between successive crests in a sinusoidal wave train; the period is the inverse of the frequency of a cyclic event. Plate tectonics: A geological model in which the Earth’s crust and uppermost mantle are divided into a number of more-or-less rigid segments. Precursor: A change in the geological conditions that is a forerunner to earthquake generation on a fault. Quaternary: About 2 million years before the present. P wave: The primary wave or fastest wave travelling away from a seismic event through the rock and consisting of a train of compressions and dilatations of the material. Probability: The number of cases that actually occur divided by the total number of cases possible. Resonance: The largest vibration of a mechanical system (such as a soil layer) due to enhancement of the energy at a frequency special to that system. Risk (Seismic): The relative risk is the comparative earthquake hazard from one site to another. The probabilistic risk is the odds of earthquake occurrence within a given time interval and region. Seismic Wave: An elastic wave in the Earth usually generated by an earthquake source or explosion. Seismicity: The occurrence of earthquakes in space and time. Seismology: The study of earthquakes, seismic sources, and wave propagation through the Earth. Slip: The relative motion of one face of a fault relative to the other. Strain: The geometrical deformation or change in shape of a body. The change in an angle, length, area, or volume divided by the original value. Stress: A measure of the forces acting on a body in units of force per unit area. Surface waves: Seismic waves that follow the Earth’s surface only, with a speed less than that of S waves. S Waves: The secondary seismic wave, travelling more slowly than the P wave and consisting of elastic vibrations transverse to the direction of travel.It cannot propagate in a liquid. Tectonic Earthquakes: Earthquakes resulting from sudden release of energy stored by major deformation of the Earth. Tectonics: Large-scale deformation of the outer part of the Earth. Earthquake energy: The maximum eneregy is generated by slipping of the fault multiflied by the volume of the rock under accerelation. A table has been prepared by Dr. B.Ramalingeswara Rao, Sr.Scientist, to compare all the energy calculations to compare them instantly and also know more about the thousands of times higher to the next unit in certain places in the Table given below
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