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28 Cards in this Set
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aftershock, p 331
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A smaller earthquake that follows the main earthquake. An aftershock has its epicenter near the epicenter of the origianl larger earthquake.
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body wave, p 334
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Any seismic wave that travels through the earth's interior (the body of the Earth), rather than along its surface. Compare with surface wave.
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earthquake, p 329
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A movement within the Earth's crust or mantle, caused by the sudden rupture or repositioning of underground rocks as they release stress
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elastic rebound, p 331
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The theory that movement along a fault is the result of an abrupt release of a progressively increasing elastic strain between the rocks on either side of the fault.
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the idea that strain can be stored for an indefinite time is at the heart of the elastic rebound theory
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epicenter, p 337
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The location on the Earth's surface that is directly above the focus of an earthquake
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fault, p 330
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a break in a rock mass along which movement has occurred.
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The surface of rock rupture along which there has been differential movement of the rock on either side.
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fault creep, p 333
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gradual displacement along a fault. Such activity occurs relatively smoothly and with little noticeable seismic activity.
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Fault creep is a continuous movement because tectonic deformation is "chronic" and ongoing. Faults that are creeping do not routinely have large earthquakes.
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focus, p 329
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the zone within the earth where rock displacement produces an earthquake
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At this point within the Earth strain energy is initially released and converted to seismic wave energy.
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foreshock, p 331
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small earthquakes preceeding a major earthquake
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Foreshocks are minor tremors before an earthquake. An increase in foreshock seismicity and frequency may signal that a major release of strain energy is imminent.
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hypocenter, p. 329
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see "focus"
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intertia, p 334
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The tendency of a body to resist acceleration . A moving body keeps moving at a constant speed in the same direction. A stationary body remains in one place, unless acted upon by an outside force.
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intensity, p 340
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A measure of the size of an earthquake based on reports about the damage it causes. Intensity is based on subjective judgment and not on quantitative measurements.
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liquefaction, p 345
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The transformation of a soil from a solid to a liquid state caused by fluid injection.
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Soils undergoing liquefaction are less able to support buildings and bridge foundations. Thus, buildings and bridges "tip sideways" during earthquakes, as soils undergo liquefaction.
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long (L) waves, p 335
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x
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magnitude, p 340
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A measure of the strength of an earthquake based on the amount of movement recorded by a seismograph .
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Modified Mercalli Intensity Scale, p 341
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earthquake-measuring scale: a scale for measuring the intensity of earthquakes, ranging from 1 to 12, in which 1 denotes a weak earthquake and 12 one that causes complete destruction.
The Mercalli scale is NOT quantitative. It is a subjective scale evaluating how the earth and earth materials and buildings reacted to the shaking. |
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moment magnitude, p 343
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The magnitude is a number that characterizes the relative size of an earthquake. Magnitude is based on measurement of the maximum motion recorded by a seismograph. Several scales have been defined, but the most commonly used are (1) local magnitude (ML), commonly referred to as "Richter magnitude," (2) surface-wave magnitude (Ms), (3) body-wave magnitude (Mb), and (4) moment magnitude (Mw). Scales 1-3 have limited range and applicability and do not satisfactorily measure the size of the largest earthquakes. The moment magnitude (Mw) scale, based on the concept of seismic moment, is uniformly applicable to all sizes of earthquakes but is more difficult to compute than the other types. All magnitude scales should yield approximately the same value for any given earthquake
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primary (P) waves, p 334
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A P wave, or compressional wave, is a seismic body wave that shakes the ground back and forth in the same direction and the opposite direction as the direction the wave is moving.
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Richter scale, p. 341
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A commonly used measure of earthquake magnitude , based on a logarithmic scale. Each integral step on the scale represents a tenfold increase in the extent of ground shaking, as recorded on a seismograph.
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The Richter scale is not subjective like the Mercalli scale.
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secondary (S) waves, p. 334
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An S wave, or shear wave, is a seismic body wave that shakes the ground back and forth perpendicular to the direction the wave is moving.
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seismic gaps, p. 353
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A segment of an active fault zone that has not experienced a major earthquake during a time period when most other segments of the zone have. Generally regarded as having a higher potential for future earthquakes.
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seismic sea wave, p 345
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A sea wave produced by any large-scale, short duration disturbance on the seafloor, commonly a shallow submarine earthquake but possibly also a submarine slide or volcanic eruption.
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also called "tsunami"
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seismogram, p 334
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The recording made by a seismograph, aninstrument that detects, magnifies, and records vibrations of the Earth, especially earthquake motion.
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seismograph, p 334
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An instrument that detects, magnifies, and records vibrations of the Earth, especially earthquakes.
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seismology, p 333
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The study of earthquakes, and of the structure of the Earth by both natural and artificially generated seismic waves.
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surface wave, p 334
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A surface wave is a seismic seismic wave that is trapped near the surface of the earth.
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tsunami, p 345
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same as "seismic sea wave"
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Wadati-Benioff zones, p 340
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An inclined plane, roughly coincident with a subduction zone, along which the foci of earthquakes cluster.
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