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Inside Earth 2:2
Ch. 2:2 Measuring Earthquakes
Term | Definition |
---|---|
Focus | The point beneath Earths surface where rock breaks under stress and causes an earthquake. |
Epicenter | Point on the Earth's surface directly above the earthquake's focus. |
Seismic waves | Vibrations that travel through the Earth carrying the energy released during an earthquake. |
P-Wave | (P=primary) A type of seismic wave that compresses and expands the ground. It is the fastest seismic wave. |
S-Wave (Secondary) | A type of seismic wave that moves the ground up and down or side to side. S-Waves are slower than P-waves and can't travel through liquid. |
Surface wave | Type of seismic wave that forms when P and S waves reach Earth’s surface. Causes the most damage. |
Seismograph | A machine that records ground movements caused by seismic waves as they move through the Earth. |
Magnitude | Measurement of earthquake strength based on seismic waves and movement along faults. |
Mercalli scale | A scale that rates earthquakes according to how much damage they cause at a particular place. |
Richter scale | *Scale for measuring earthquakes,* Each step in scale is 10 times more powerful than the step below. |
Moment magnitude scale | A rating system that estimates the total energy released by an earthquake. Used today. |