Synonym: Primary wave (p-wave) = Compressional wave
A body wave caused by oscillation of a normal stress in a matter and as such resulting in strain oscillations along the direction of p-wave propagation.
In terms of corpuscular structure of the matter the p-wave is characterised by the fact that particles of the matter are moving back and forth along the p-wave travel direction (see Fig. 1).
P-wave can
One of the two main types of elastic body waves, called seismic waves in seismology (see p-wave @ Wikipedia).
P-waves can propagate through gases, liquids or solids and move moves faster than other body waves (almost twice faster than s-wave).
When all body waves are excited at the same time the p-wave is the first arrival to the sensor, hence the name "primary".
See also
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Physics / Mechanics / Continuum mechanics / Mechanical waves / Body wave
[ s-wave ]