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chapter 19
Vocabulary
| Term | Definition |
|---|---|
| stress | forces per unit area taht act on material compression tension and shear. |
| strain | deformation of materials in response to stress |
| elastic deformation | causes material to bend and stretch;proportational to stress, so if the stress is reduced or returns to zero the strain or deformation is reduced or disappears. |
| plastic deformation | permanent deforamtion casued by strain when stress exceeds a certain |
| fault | fracture or system of fractures in Earth's crust that occurs when stress is applied too quickly or stress is too great; can form as a result of horizontal compression |
| seismic wave | the vibration of the ground during an earthquake |
| primary wave | seismac wave that squeezes and pushes rocks int he same direction that the wave travels known as p wave |
| secondary wave | seismic wave that causes rock particles move at the right angles to thedirection of the wave,known as an s wave |
| focus | point of theinitial fault repture where an earthquake originates that usually lies at least several kilometers beneath earth's surface |
| epicenter | point on earth's surface directly a above the focus of an earthquake |
| seismeter | instruction used to measure horizontal or verical motion during an earthquake. |
| seismogram | record produced by a seissmometer that can provide individual tracking of each type of seismic wave |
| richter scale | numerical rating system used to measure the amount of energy released during an earthquake |
| magnitude | measure of the energy released during an earthquake, which can be described using the richter scale |
| amplitude | the size of rhe seismic waves; an increase of 1 in the scale reprsenets an increawse in amplitude of a factor of 10 |
| moment magnitude scale | scale suded to measure earthquake magnitude taking into account the size of the fault reputure the rocks stiffness and amound of movement aling the fault |
| modified mercelli scale | measure earthquake intensity on a scale from 1 to 5 |
| soil liquefaction | process associated with seismic vibrations that occur in areas of sand that is nearly saturated; resulting in the ground behaving like a liquid |
| tsunami | large powerful ocean wave generated by the vertical motions of the seafloor during an earthquake; in shallow water, can form huge. |
| seismic gap | place along an active fault that hass nt experienced an earthquake for a long time. |