Q:

What is the definition of "seismic activity"?

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Quick Answer

"Seismic activity" is defined as the vibration of the ground due to the release of elastic energy from the breakage of rock within the earth or an explosion. The phenomenon is commonly referred to as an earthquake, but while seismic waves can be either body waves or surface waves, an earthquake radiates seismic energy as both types of waves.

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Full Answer

Most seismic activity is caused by the movement of tectonic plates. As these plates shift, rocks around the boundaries of the plates are deformed, which then causes elastic energy to be stored. When pressure leads to a fault segment slipping, the results can be extraordinary. Seismic activity has many other causes as well, including crustal loading, volcanic or hydrothermal activity, and the re-activation of very old faults.

Humans may also cause seismic activity through fluid injection, reservoir filling or demolitions. To record seismic wave motion, scientists measure seismic activity with a seismograph, which is a very sensitive instrument that very accurately reads the magnitude and location of the seismic activity being picked up.

While it may be very destructive, seismic activity is also responsible for many treasured landscapes and topographic locations that people enjoy for their beauty and unique features. Many national parks, for example, are in areas where large earthquakes or other plate tectonic activity occurred in the past.

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Related Questions

  • Q:

    What causes seismic waves?

    A:

    Seismic waves occur from actions within the Earth's core, including breaking and splitting rocks, explosions and volcanic eruptions. Seismic waves occur on land and in the ocean; they exist in two primary forms — surface waves and body waves. Body waves travel underground, below the Earth's surface, while surface waves travel across the surface.

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  • Q:

    What are three types of seismic waves?

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    The three types of seismic waves are primary waves, secondary waves and surface waves. Seismic waves can cause earthquakes and have destructive capability. Primary and secondary waves are known as body waves, and these waves penetrate the interior of the Earth, whereas surface waves do not penetrate the Earth.

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  • Q:

    What does a seismometer measure?

    A:

    A seismometer measures movements in the ground during an earthquake and creates electric signals that can be read to determine an earthquake's magnitude. Seismometers are contained within a device called a seismograph that is attached to the ground.

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  • Q:

    When do earthquakes occur?

    A:

    Earthquakes are usually triggered when rock located beneath the ground, on top of fault lines, breaks and suddenly releases a significant amount of energy. The immediate and rapid release of energy caused by earthquakes generates seismic waves, which cause shaking motions that start below the Earth’s surface and spread across large distances.

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