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Chapter 19
| Term | Definition |
|---|---|
| Stress | Total force acting on crustal rocks per unit area. |
| Strain | Deformation of materials in response to stress. |
| Elastic deformation | Is caused when a material is compressed, bent, or stretched. |
| Plastic deformation | When stress builds up past a certain point, called the elastic limit, rock undergo. |
| Fault | Is any fracture of system of fractures along which Earth moves. |
| Seismic waves | Vibrations of the ground produced during an earthquake. |
| Primary waves | Squeeze and push rocks in the direction along which the waves are traveling. |
| Secondary waves | They are slower than P-waves, so they are the second set of waves to be felt. |
| Focus | Is usually several kilometers below Earths surface. |
| Epicenter | Point on Earths surface directly above focus. |
| Seismometers | Consist of a rotating drum covered with a sheet of paper, a pen or other such recording tool, and a mass, such as pendulum. |
| Seismogram | Record produced by a seismometer. |
| Richter scale | Devised by a geologist named Charles Richter, is a numerical rating system that measures the energy of the largest seismic waves. |
| Magnitude | Produced during a earthquake. |
| Amplitude | The largest seismic wave. |
| Moment magnitude scale | Is a rating scale that measures the energy released by a earthquake, taking into account the size. |
| Modified Mercalli scale | Which rates the type of damage they cause. |
| Soil liquefaction | Vibrations can cause the ground to behave like a liquid in a phenomenon. |
| Tsunami | A large ocean wave generated by vertical motions of the sea floor during an Earth quake. |
| Seismic gaps | Are sections located along faults that are known to be active, but which have not experienced significant earthquakes for a long time. |