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ACCELEROGRAPH  look up translate image
A seismograph whose output is proportional to ground acceleration (in comparison to the usual seismograph whose output is proportional to ground velocity). Accelerographs are typically used as instruments designed to record very strong ground motion useful in engineering design; seismographs commonly record off scale in these circumstances. Normally, strong motion instruments do not record unless triggered by strong ground motion. (Noson, et.al., 1988)
AFTERSHOCK  look up translate image
One of many earthquakes that often occur during the days to months after some larger earthquake (mainshock) has occurred. Aftershocks occur in the same general region as the mainshock and are believed to be the result of minor readjustments of stress at places in the fault zone. (Noson, et.al., 1988) An earthquake which follows a larger earthquake or main shock and originates in or near the rupture zone of the larger earthquake. Generally, major earthquakes are followed by a larger number of aftershocks, decreasing in frequency with time. (USGS National Earthquake Information Center, 1999)
AMPLITUDE  look up translate image
The amplitude of a seismic wave is the amount the ground moves as the wave passes by. (As an illustration, the amplitude of an ocean wave is one-half the distance between the peak and trough of the wave. The amplitude of a seismic wave can be measured from the signal recorded on a seismogram.) (Noson, et.al., 1988) The maximum height of a wave crest of depth of a trough. (USGS National Earthquake Information Center, 1999)
BROAD BAND SEISMIC STATION  look up translate image

CRUST  look up translate image
The Earth's outermost layer. (Teacher's Packet)
DEEP EARTHQUAKES  look up translate image
...deep earthquakes and those located away from the volcano, which produce high-frequency signatures and sharp arrivals similar to tectonic earthquakes (Brantley and Topinka, 1984)
EARTHQUAKE  look up translate image
Shaking of the Earth caused by a sudden movement of rock beneath its surface. (USGS National Earthquake Information Center, 1999) The release of stored elastic energy caused by sudden fracture and movement of rocks inside the Earth. Part of the energy released produces seismic waves, like P, S, and surface waves, that travel outward in all directions from the point of initial rupture. These waves shake the ground as they pass by. An earthquake is felt if the shaking is strong enough to cause ground accelerations exceeding approximately 1.0 centimeter/second squared. (Noson, et.al., 1988)
EARTHQUAKE SWARM  look up translate image
A series of minor earthquakes, none of which may be identified as the main shock, occurring in a limited area and time. (USGS National Earthquake Information Center, 1999)
EPICENTER  look up translate image
That point on the Earth's surface directly above the hypocenter of an earthquake. (USGS National Earthquake Information Center, 1999) The location on the surface of the Earth directly above the focus, or place where an earthquake originates. An earthquake caused by a fault that offsets features on the Earth's surface may have an epicenter that does not lie on the trace of that fault on the surface. This occurs if the fault plane is not vertical and the earthquake occurs below the Earth's surface. (Noson, et.al., 1988)
FAULT  look up translate image
A break in the Earth along which movement occurs. Sudden movement along a fault produces earthquakes. Slow movement produces aseismic creep. (Noson, et.al., 1988)
FOCUS  look up translate image
That point within the Earth from which originates the first motion of an earthquake and its elastic waves. (USGS National Earthquake Information Center, 1999)
FORESHOCK  look up translate image
A small tremor that commonly precedes a larger earthquake or main shock by seconds to weeks and that originates in or near the rupture zone of the larger earthquake. (USGS National Earthquake Information Center, 1999)
HARMONIC TREMOR  look up translate image
Continuous rhythmic earthquakes in the Earth's upper lithosphere that can be detected by seimographs. Harmonic tremors often precede or accompany volcanic eruptions. (Teacher's Packet) A continuous release of seismic energy typically associated with the underground movement of magma. It contrasts distinctly with the sudden release and rapid decrease of seismic energy associated with the more common type of earthquake caused by slippage along a fault. (Foxworthy and Hill, 1982) ... harmonic...(more)
HYPOCENTER  look up translate image
The calculated location of the focus of an earthquake. (USGS National Earthquake Information Center, 1999)
INTENSITY  look up translate image
A measure of severity of shaking at a particular site. It is usually estimated from descriptions of damage to buildings and terrain. The intensity is often greatest near the earthquake epicenter. Today, the Modified Mercalli Scale is commonly used to rank the intensity from I to XII according to the kind and amount of damage produced. Before 1931 earthquake intensities were often reported using the Rossi-Forel scale. (Noson, et.al., 1988) A measure of the effects of an earthquake at a particular...(more)
INTENSITY SCALE  look up translate image
The effect of an earthquake on the Earth's surface is called the intensity. The intensity scale consists of a series of certain key responses such as people awakening, movement of furniture, damage to chimneys, and finally - total destruction. Although numerous intensity scales have been developed over the last several hundred years to evaluate the effects of earthquakes, the one currently used in the United States is the Modified Mercalli (MM) Intensity Scale. (USGS National Earthquake Information Center, 1999)
LG WAVE  look up translate image
A surface wave which travels through the continental crust. (USGS National Earthquake Information Center, 1999)
LONG-PERIOD EARTHQUAKES  look up translate image
... low-frequency earthquakes (called long-period or volcanic), which reflect adjustments related to the exit of magma from the summit reservoir to feed the eruption ... (Tilling, et.al., 1987)
LOVE WAVE  look up translate image
A major type of surface wave having a horizontal motion that is shear or transverse to the direction of propagation (travel). It is named after A.E.H. Love, the English mathematician who discovered it. (USGS National Earthquake Information Center, 1999)
MAGNITUDE  look up translate image
A quantity characteristic of the total energy released by an earthquake, as contrasted with intensity, which describes its effects at a particular place. A number of earthquake magnitude scales exist, including local (or Richter) magnitude, body wave magnitude, surface wave magnitude, moment magnitude, and coda magnitude. As a general rule, an increase of one magnitude unit corresponds to ten times greater ground motion, an increase of two magnitude units corresponds to 100 times greater ground...(more)
MAINSHOCK  look up translate image
The largest in a series of earthquakes occurring closely in time and space. The mainshock may be preceded by foreshocks or followed by aftershocks. (Noson, et.al., 1988)
MANTLE  look up translate image
A zone in the Earth's interior between the crust and the core that is 2,900 kilometers (1,740 miles) thick. (The lithosphere is composed of the topmost 65-70 kilometers (39-42 miles) of mantle and the crust). (Teacher's Packet)
MICROEARTHQUAKES  look up translate image
Earthquakes with magnitude of about 2.0 or less are usually call microearthquakes; they are not commonly felt by people and are generally recorded only on local seismographs. (USGS National Earthquake Information Center, 1998)
MODIFIED MERCALLI INTENSITY SCALE  look up translate image
The effect of an earthquake on the Earth's surface is called the intensity. The intensity scale consists of a series of certain key responses such as people awakening, movement of furniture, damage to chimneys, and finally - total destruction. Although numerous intensity scales have been developed over the last several hundred years to evaluate the effects of earthquakes, the one currently used in the United States is the Modified Mercalli (MM) Intensity Scale. It was developed in 1931 by the American...(more)
P (PRIMARY) WAVES  look up translate image
Also called compressional or longitudinal waves, P waves are the fastest seismic waves produced by an earthquake. They oscillate the ground back and forth along the direction of wave travel, in much the same way as sound waves, which are also compressional, move the air back and forth as the waves travel from the sound source to a sound receiver. (USGS National Earthquake Information Center, 1998)
PLATE TECTONICS  look up translate image
A widely accepted theory that relates most of the geologic features near the Earth's surface to the movement and interaction of relatively thin rock plates. The theory predicts that most earthquakes occur when plates move past each other. (Noson, et.al., 1988)
PLATES  look up translate image
Pieces of crust and brittle uppermost mantle, perhpas 100 kilometers thick and hundres or thousands of kilometers wide, that cover the Earth's surface. The plates move very slowly over, or possibly with, a viscous layer in the mantle at rates of a few centimeters per year. (Noson, et.al., 1988)
RAYLEIGH WAVE  look up translate image
A type of surface wave having a retrograde, elliptical motion at the Earth's surface, similar to the waves caused when a stone is dropped into a pond. These are the slowest, but often the largest and most destructive, of the wave types caused by an earthquake. They are usually felt as a rolling or rocking motion and in the case of major earthquakes, can be seen as they approach. Named after Lord Rayleigh, the English physicist who predicted its existence. (USGS National Earthquake Information Center, 1999)
RICHTER MAGNITUDE SCALE  look up translate image
The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions....(more)
S (SECONDARY OR SHEAR) WAVES  look up translate image
S waves oscillate the ground perpendicular to the direction of wave travel. They travel about 1.7 times slower than P waves. Because liquids will not sustain shear stresses, S waves will not travel through liquids like water, molten rock, or the Earth's outer core. (USGS National Earthquake Information Center, 1998)
SEICHE  look up translate image
A standing wave in a closed body of water such as a lake or bay. It can be characterized as the sloshing of water in the enclosing basin. Seiches can be produced by seismic waves from earthquakes. The permanent tilting of lake basins caused by nearby fault motions has produced very entergetic seiches. (Noson, et.al., 1988)
SEISMIC WAVES  look up translate image
A vibrational disturbance in the Earth that travels at speeds of several kilometers per second. There are three main types of seismic waves in the earth P (fastest), S (slower), and Surface waves (slowest). Seismic waves are produced by earthquakes. (Noson, et.al., 1988) Seismic waves are the vibrations from earthquakes that travel through the Earth; they are recorded on instruments called seismographs. (USGS National Earthquake Information Center, 1998)
SEISMICITY  look up translate image
Earthquake activity. (USGS National Earthquake Information Center, 1999)
SEISMOGRAM  look up translate image
A graph showing the motion of the ground versus time. (Noson, et.al., 1988) A written record of an earthquake, recorded by a seismograph. (USGS National Earthquake Information Center, 1999)
SEISMOGRAPH  look up translate image
A sensitive instrument that can detect, amplify, and record ground vibrations too small to be perceived by human beings. (Noson, et.al., 1988) An instrument that records the motions of the Earth, especially earthquakes. (USGS National Earthquake Information Center, 1999) A scientific instrument that detects and records vibrations (seismic waves) produced by earthquakes. (Teacher's Packet)
SEISMOGRAPH STATION  look up translate image
A site at which one or more seismographs are set up and routinely monitored. (USGS National Earthquake Information Center, 1999)
SEISMOLOGIST  look up translate image
A scientist who studies earthquakes. (USGS National Earthquake Information Center, 1999)
SEISMOMETRY  look up translate image
The instrumental aspects of seismology. (USGS National Earthquake Information Center, 1999)
SHALLOW EARTHQUAKES  look up translate image
... shallow earthquakes, located under the dome at depths of less than 3 kilomenters, which produce medium-to low-frequency seismic arriavals ... (Brantley and Topinka, 1984)
SHORT PERIOD SEISMIC STATION  look up translate image

SHORT-PERIOD EARTHQUAKES  look up translate image
... During inflation the rocks surrounding the (magma) reservoir become stressed, and this stress is partly relieved by increasing numbers of earthquakes, too small to be felt, but easily recorded by seismometers at Kilauea (Hawaii) summit. These earthquakes (called short-period or tectonic) are recorded as high-frequency features on a seismograph ... (Tilling, et.al., 1987)
SPREADING CENTER  look up translate image
An elongated region where two plates are being pulled away from each other. New crust is formed as molten rock is forced upward into the gap. Examples of spreading centers include the Mid-Atlantic Ridge and the East African Rift. (USGS National Earthquake Information Center, 1999)
STRONG MOTION SEISMIC STATION  look up translate image

SUBDUCTION ZONE  look up translate image
The place where two lithosphere plates come together, one riding over the other. Most volcanoes on land occur parallel to and inland from the boundary between the two plates. (Teacher's Packet)
SUBDUCTION ZONE BOUNDARY  look up translate image
The region between converging plates, one of which dives beneath the other. The Cascadia subduction zone boundary is an example. (Noson, et.al., 1988)
SURFACE EVENTS  look up translate image
... surface events, such as gas and tephra events, rockfalls associated with dome growth, and snow and rock avalanches from the crater walls, which produce complicated signatures with no clear beginning or end ... (Brantley and Topinka, 1984)
SURFACE WAVES  look up translate image
Waves that move over the surface of the Earth. Rayleigh waves and Love waves are surface waves. (USGS National Earthquake Information Center, 1999) Seismic waves, slower than P or S waves, that propagate along the Earth's surface rather than through the deep interior. Two principal types of surface waves, Love and Rayleigh waves, are generated during an earthquakes. Rayleigh waves cause both vertical and horizontal ground motion, and Love waves cause horizontal motion only. They both produce...(more)
TECTONIC  look up translate image
Pertaining to the forces involved in the deformation of the Earth's crust, or the structures or features produced by such deformation.
TECTONIC EARTHQUAKES  look up translate image
Although all earthquakes associated with active volcanoes are ultimately related to volcanic processes, Volcanic earthquakes are directly associated with magma movement, while tectonic earthquakes occur in zones separated from the principal areas of magma movement. (Heliker, et.al., 1986)
TREMOR  look up translate image
See Harmonic tremor.
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Earthquake terminology
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Created on 2011-05-13 02:05:08
Number of terms 53
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Sources
  • Animations for Earthquake Terms and Concepts
    earthquake.usgs.gov
    USGS Earthquake Hazards Program, responsible for monitoring, reporting, and researching earthquakes and earthquake hazards
  • CVO Menu - Glossary of Earthquake and Related Terminology
    vulcan.wr.usgs.gov
  • Earthquake Glossary
    earthquake.usgs.gov
    USGS Earthquake Hazards Program, responsible for monitoring, reporting, and researching earthquakes and earthquake hazards
  • Glossary of Earthquake Terms
    earthquake-report.com
  • ScienceMaster - Physical Science - Glossary of Earthquake Terms
    www.sciencemaster.com
    Glossary of Earthquake Terms
  • Untitled Document
    mbmgquake.mtech.edu