Seismic wave

This article is about waves that travel through Earth. For ocean waves sometimes called "seismic sea waves", see Tsunami.
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p-wave and s-wave from seismograph
Velocity of seismic waves in Earth versus depth.[1] The negligible S-wave velocity in the outer core occurs because it is liquid, while in the solid inner core the S-wave velocity is non-zero

A seismic wave is a mechanical wave of acoustic energy that travels through the Earth or another planetary body. It can result from an earthquake (or generally, a quake), volcanic eruption, magma movement, a large landslide and a large man-made explosion that produces low-frequency acoustic energy. Seismic waves are studied by seismologists, who record the waves using seismometers, hydrophones (in water), or accelerometers. Seismic waves are distinguished from seismic noise (ambient vibration), which is persistent low-amplitude vibration arising from a variety of natural and anthropogenic sources.

The propagation velocity of a seismic wave depends on density and elasticity of the medium as well as the type of wave. Velocity tends to increase with depth through Earth's crust and mantle, but drops sharply going from the mantle to Earth's outer core.[2]

Earthquakes create distinct types of waves with different velocities. When recorded by a seismic observatory, their different travel times help scientists locate the quake's hypocenter. In geophysics, the refraction or reflection of seismic waves is used for research into Earth's internal structure. Scientists sometimes generate and measure vibrations to investigate shallow, subsurface structure.

  1. ^ G. R. Helffrich & B. J. Wood (2002). "The Earth's mantle" (PDF). Nature. 412 (2 August). Macmillan Magazines: 501–7. doi:10.1038/35087500. PMID 11484043. S2CID 4304379. Archived (PDF) from the original on 24 August 2016.
  2. ^ Shearer 2009, Introduction