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Measuring Earthquake
Inside Earth: Chapter Two, Section Two
Term | Definition |
---|---|
focus | the point beneath Earth's surface where rock breaks under stress and causes an earthquake. |
epicenter | the point on Earth's surface directly above an earthquake's focus. |
seismic waves | a vibration that travels through Earth carrying the energy released during an earthquake. |
P waves | a type of seismic wave that compresses and expands the ground; primary. |
S waves | a type of seismic wave that moves the ground up and down or side to side; secondary. |
surface waves | a type of seismic wave that forms when P waves and S waves reach Earth's surface. |
seismograph | a device that records ground movements caused by seismic waves as they move through Earth. |
magnitude | the measurement of an earthquake's strength based on seismic waves and movement along faults. |
Mercalli scale | a scale that rates earthquakes according to their intensity and how much damage they cause. |
Richter scale | a scale that rates seismic waves as measured by a particular type of mechanical seismograph |
moment magnitude scale | a scale that rates earthquakes by estimating the total energy released by an earthquake; the scale commonly used today. |