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Chapter 19 Vocab
Vocab
Term | Definition |
---|---|
Stress | Forces per unit area that act on a material- compression,tension, and shear |
Strain | deformation of materials in response to stress |
Elastic Deformation | Causes materials to bend and stretch; proportional to stress, so if the stress is reduced or returns to zero the strain or deformation is reduced or disapears |
plastic deformation | Permanent deformation caused by strain when stress exceeds a certain value |
Fault | Fracture or system of fractures in earth's crust that occurs when stress is applied too quickly or stress is too great |
Seismic waves | The vibrations of the ground during an earthquake |
Primary waves | seismic wave that squeezes and pushes rocks in the same direction that the wave travels, know as a p-wave |
Secondary waves | Seismic wave that causes rock particles to move at right angles to the direction of the wave, known as an s-wave |
Focus | Point of the initial fault rupture where an earthquake originates that usually lies at least several kilometers beneath earth's surface |
Epicenter | Point on earth's surface directly above the focus of an earthquake |
Seismometers | instrument used to measure horizontal or vertical motion during an earthquake |
Seismogram | Record produced by a seismometer 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 energy released during an earthquake, which can be described using richer scale |
Amplitude | The size of the seismic waves; an increase of 1 in the scale represents an increase in amplitude of a factor of 10 |
Moment Magnitude Scale | Scale used to measure earthquake magnitude- taking into account the size of the fault rupture |
Modified Mercalli scale | Measures earthquakes intensity on a scale from 1 to 10 |
Soil Liquefaction | Process associated with seismic vibrations that occur in areas of sand that is nearly saturated;resulting in the ground behaving like liquid |
Tsunami | Large powerful ocean wave generated by the vertical motions of the seafloor during an earthquake |
Seismic Gaps | place along an active fault that has not experienced an earthquake for a long time |