Gelombang-P: Perbedaan antara revisi
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[[Berkas:Onde compression impulsion 1d 30 petit.gif|thumb|305px|Gelombang-P datar.]]
[[Berkas:Ondes compression 2d 20 petit.gif|thumb|305px|Representasi penjalaran gelombang-P pada sebuah ''grid'' 2-dimensi (bentuk empiris).]]
One of the two types of elastic [[body wave (seismology)|body wave]]s (named because they travel through the body of the [[Earth]]) that are produced by [[earthquake]]s and recorded by [[seismometer]]s. The name primarily comes from the fact that they have the highest velocity of all seismic waves and are thus the first to arrive at any seismic station, the other body wave type being [[S-wave|S- or secondary waves]]. [[Sound]], as a [[pressure]] wave and a [[longitudinal wave]], is also a P-wave. This means that the particles in the body of the Earth have vibrations along or parallel to the direction of travel of the wave energy.
[[Image:Earthquake wave shadow zone.gif|thumb|150px|P-wave shadow zone (from [[USGS]])]]
:<math>v_p= \sqrt{ \frac {k+\frac{4}{3}\mu} {\rho}} </math>
where:
* ''k'' is the [[bulk modulus|modulus of incompressibility]]
* ''<math>\mu</math>'' is the [[modulus of rigidity]]; and
* ''<math>\rho</math>'' the [[density]] of the material through which the wave is propagating
Of these density shows the least variation so the velocity is mostly controlled by k and μ
Almost all the information we have on the structure of the Earth's deep interior is derived from observations of the travel times, [[Reflection (physics)|reflection]]s, [[refraction]]s and phase transitions of seismic body waves, or [[normal modes]]. Body waves travel through the fluid layers of the [[Earth#Interior|Earth's interior]], but P-waves are refracted slightly when they pass through the transition between the semisolid [[mantle (geology)|mantle]] and the liquid [[Earth#The core|outer core]]. As a result, there is a P-wave "shadow zone" between 104° and 140°, where the initial P-waves are not registered on [[seismometer]]s. In contrast, "S" waves do not travel through liquids, rather, they are attenuated.
==See also==
* [[Longitudinal wave]]
* [[S-wave]]
* [[Rayleigh waves]]
* [[Love wave]]
==References==
{{cite web|url=http://earthquake.usgs.gov/image_glossary/shadow_zone.html|work=U.S. Geological Survey"|title="Photo Glossary of Earthquakes"|accessdate=October 10|accessyear=2005}}
==External links==
*[http://www.eas.purdue.edu/~braile/edumod/waves/WaveDemo.htm Purdue's catalog of animated illustrations of seismic waves]
'''Gelombang P''' adalah [[gelombang]] yang arah simpangannya searah dengan arah rambatannya. Sebagai contoh adalah sebuah [[pegas]], bila kita beri gaya dorong maka pegas akan merambatkan [[energi]] dengan cara merapat dan perengangkan pegas, dan searah dengan arah rambatannya.
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