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Inside Earth 2:2
Ch. 2 Sec. 2 Measuring Earthquakes
Question | Answer |
---|---|
focus | The point beneath Earth’s 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 | (S=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 cannot travel through a 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 | a scale for measuring earthquakes, and 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. |