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chapter 7
Term | Definition |
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Earthquake | a sudden and violent shaking of the ground, sometimes causing great destruction, as a result of movements within the earth's crust or volcanic action. |
Focus | The location where the earthquake begins. The ground ruptures at this spot, then seismic waves radiate outward in all directions. Under the ground. |
Epicenter | the point on the earth's surface vertically above the focus of an earthquake. |
Tsunami | a long high sea wave caused by an earthquake. |
Fault | a place where sections of the crust of the Earth move relative to each other. |
Normal Fault | Occur where two blocks of rock are pulled apart, as by tension. |
Reverse Fault | Occur where two blocks of rock are forced together by compression. |
Strike-Slip Fault | a fault in which rock strata are displaced mainly in a horizontal direction, parallel to the line of the fault. |
Seismic Wave | an elastic wave in the earth produced by an earthquake. |
Primary Wave | are alternatingly compressional and extensional, and cause the rocks they pass through to change in volume. These waves are the fastest traveling seismic waves and can travel through solids, liquids, and gases. |
Secondary Wave | a wave motion in a solid medium where the medium moves perpendicular to the direction of the travel of the wave. |
Surface Wave | A seismic wave that travels across the surface of the Earth as opposed to through it. Usually have larger amplitudes and longer wavelengths than body waves, and they travel more slowly than body waves do. |
Seismograph | an instrument that measures and records details of earthquakes, such as force and duration. |
Magnitude | Is a number that characterizes the relative size of an earthquake. Is based on measurement of the maximum motion recorded by a seismograph. |