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A body wave caused by oscillation of a shear shear stress in a matter and as such resulting in in strain oscillations perpendicular to the direction of s-wave propagation.
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S-wave can propagate through solids only and move slower than p-wave.
When all body waves are excited at the same time the s-wave arrives after the p-wave to the sensor, hence the name "secondary".
See also
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Physics / Mechanics / Continuum mechanics / Mechanical waves / Body wave
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