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| A sudden movement of the earth's crust caused by the release of stress accumulated along geologic faults or by volcanic activity. Also called seism, temblor. |
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elastic rebound theory [image] |
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| After the devastating 1906 San Francisco, California earthquake, a fault trace was discovered that could be followed along the ground in a more or less straight line for 270 miles. It was found that the earth on one side of the fault had slipped compared to the earth on the other side of the fault by up to 21 feet (7 m). This fault trace drew the curiosity of a number of scientists, especially since nobody had yet been able to explain what was happening within the earth to cause earthquakes. Up until this earthquake, it had generally been assumed that the forces leading to the occurrence of earthquakes must be close to the locations of the earthquakes themselves. |
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| Also, epicentrum. Geology. a point, directly above the true center of disturbance, from which the shock waves of an earthquake apparently radiate. |
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| the discontinuity between the crust and the mantle of the earth, occurring at depths that average about 22 mi. (35 km) beneath the continents and about 6 mi. (10 km) beneath the ocean floor. |
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| a scale, ranging from 1 to 10, for indicating the intensity of an earthquake. |
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modified mercalli scale [image] |
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ABAG uses the modified Mercalli Intensity Scale to depict shaking severity. |
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| Seismic Deformation Although wave speeds vary by a factor of ten or more in the Earth, Variations in such slopes reveal variations in the seismic velocities of rocks. |
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| a record made by a seismograph. |
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| any of various instruments for measuring and recording the vibrations of earthquakes. |
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| The figure below shows the structure of the Earth. P and S waves travel very differently through the Earth. However, S waves cannot travel through the liquid outer core of the Earth. |
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| Survey of philosophical woories about inconsistencies inherent in the idea of time travel in the context of modern physics. From the Stanford Encyclopedia, by Tim Maudli Time travel has been a staple of science fiction. |
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P-waves are type of elastic wave, also called seismic waves, that can travel through gasses (such as sounds), elastic solids and liquids, including the Earth. P-waves can be produced by earthquakes and recorded by seismometers. The name P-wave stands for primary wave, as the P-wave is the fastest among the abusive waves, compared to the S-waves. |
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| A type of seismic wave, the S-wave, secondary wave, or shear wave (sometimes called an elastic S-wave) is one of the two main types of elastic body waves, so named because they move through the body of an object, unlike surface waves. |
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| The particle motion of a Love wave forms a horizontal line perpendicular to the direction of propagation. Moving deeper into the material, motion can decrease to a "node" and then alternately increase and decrease as one examines deeper layers of particles. The amplitude, or maximum particle motion, often decreases rapidly with depth. |
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| The R wave and the L wave are right-hand and left-hand circularly polarized, respectively. The R wave has a cut-off at ωR (hence the designation of this frequency) and a resonance at ωc. The L wave has a cut-off at ωL and no resonance. R waves at frequencies below ωc/2 are also known as whistler modes. |
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| A tsunami (pronounced /(t)suːˈnɑːmi/) is a series of waves created when a body of water, such as an ocean, is rapidly displaced. Earthquakes, mass movements above or below water, some volcanic eruptions and other underwater explosions, landslides, underwater earthquakes, large asteroid impacts and detonation of nuclear weapons at sea all have the potential to generate a tsunami. Due to the immense volumes of water and energy involved, the effects of tsunami can be devastating. Since meteorites are small, they will not generate tsunami. |
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| Seismic waves are waves that travel through the Earth or other elastic body, for example as the result of an earthquake, explosion, or some other process that imparts forces to the body. Seismic waves are also continually excited on Earth by the incessant pounding of ocean waves (referred to as the microseism) and the wind. Seismic waves are studied by seismologists, and measured by a seismograph, which records the output of a seismometer, or geophone. For seismic studies of oil reservoirs, hydrophones may give additional information. |
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| n seismology, several types of surface waves are encountered. Surface waves, in this mechanical sense, are commonly known as either Love waves (L waves) or Rayleigh waves,a seismic wave is a wave that travels through the Earth, often as the result of an earthquake or explosion. Love waves have transverse motion (movement is perpendicular to the direction of travel, like light waves), whereas Rayleigh waves have both longitudinal (movement parallel to the direction of travel, like sound waves) and transverse motion. |
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