Seismic wave

A seismic wave is an elastic disturbance that carries energy through Earth or along its surface. Earthquakes, explosions, and volcanic activity commonly generate seismic waves.

P-wave: A compressional seismic body wave that travels through solids, liquids, and gases. Its early arrival and ability to cross liquid layers distinguish it from other seismic waves.
Seismic velocity: The speed at which a seismic wave propagates through a material. Differences in velocity determine arrival times and bend rays through Earth's interior.
Seismology: The scientific study of earthquakes and the propagation of elastic waves through Earth. Seismology uses wave observations to infer earthquakes and Earth's internal structure.
Mohorovičić discontinuity: The boundary between Earth's crust and mantle, marked by a change in seismic-wave velocity. Andrija Mohorovičić identified it from contrasting arrivals of earthquake waves.
S-wave: A shear seismic body wave that travels through solids but not liquids. Its absence beyond Earth's liquid outer core helped establish that the core is liquid.
Seismic impedance: The product of a material's density and seismic-wave velocity. Impedance contrasts at boundaries control how much wave energy reflects or transmits.
Seismometer: An instrument that measures ground motion caused by seismic waves and other vibrations. Its recordings turn passing waves into measurable signals for analysis.
Lehmann discontinuity: A seismic boundary within Earth's mantle, named for the scientist who identified it. Wave observations associated with Inge Lehmann revealed a previously unknown internal boundary.
Love wave: A surface seismic wave that shears the ground horizontally, perpendicular to its direction of travel. Its strong horizontal motion can produce damaging forces during earthquakes.
Seismic reflection: The return of seismic energy from a boundary between materials with different properties. Reflected waves provide images of subsurface boundaries in exploration and seismology.

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