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Seismic waves are the waves consisting of the propagation of the deformations of an earthquake. Their study (seismology) has been a key to what is known about the Earth's internal structure. By analogy, the term is used for analogous waves in other bodies: planets, moons and stars (asteroseismology, and in the case of the Sun, helioseismology).
Conceivably, seismic waves could be classified as sound waves, being the same various types of waves that can transmit sound through a solid such as a steel beam, and one of the types does correspond to sound waves in air. Other types correspond to twisting or sideways movement, the latter somewhat like a visible wave traveling down a taut rope. The various types reveal information based upon timing of reception at various points on Earth, implying varying speeds and reflections that correspond to the configuration of various types of material within the Earth.