Seismic Waves and Earthquake Terminology

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Seismic Waves

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Waves of energy that travel through the Earth's layers, caused by earthquakes, volcanic eruptions, magma movement, large landslides, and large man-made explosions.

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P-waves

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Primary waves, which are the fastest type of seismic wave and can move through solid rock and fluids, like water or the liquid layers of the Earth.

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S-waves

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Secondary waves, which are slower than P-waves and can only move through solid rock, not through any liquid medium.

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Surface Waves

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Seismic waves that travel along the Earth's surface. They are slower than body waves (P-waves and S-waves) and are typically responsible for the damage and destruction associated with earthquakes.

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Hypocenter

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The point within the Earth where an earthquake rupture starts. Also known as the focus.

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Epicenter

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The point on the Earth's surface located directly above the hypocenter or focus of an earthquake.

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Fault Line

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A fracture or zone of fractures between two blocks of rock, which allows the blocks to move relative to each other. This movement may occur rapidly, in the form of an earthquake, or may occur slowly, in the form of creep.

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Earthquake

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The shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves.

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Seismogram

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The paper reading or a record produced by a seismograph that can provide information about the strength and duration of an earthquake.

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Seismograph

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An instrument that measures and records details of earthquakes, such as force and duration.