It is known that when a large earthquake occurs, say $M \ge 9.0$, The surface waves travel around Earth over and over, "ringing the surface like a bell". The GIF below is an example (Image Source):

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Do these normal modes cause permanent deformation AWAY from the earthquake source or does Earth affected simply slide back in place after the wave passes through it? If there is no permeant deformation, why does the surface near (but off source) crack and fault?

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    $\begingroup$ Normal modes do not cause permanent deformation but rather oscillatory deformations at anti-nodes. Therefore the simple answer is no the Earth will not be permanently deformed, but will the Earth's anti-nodes continually oscillate? Also no, because the waves will attenuate with time. $\endgroup$ – Kenshin Apr 28 '14 at 4:40
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    $\begingroup$ I thought that there is at least evidence for antipodal earthquake damage on Mars (or was it after impacts?). $\endgroup$ – tobias47n9e Apr 28 '14 at 17:02
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    $\begingroup$ "If there is no permeant deformation, why does the surface near (but off source) crack and fault?" - That's kind of implying that these surface waves are the only type of deformation caused by the earthquake. They clearly aren't (as you mention, cracks and faults happen, and presumably other non-waved based deformations result in surrounding areas to cope with those stresses), so I'm not sure if that last sentence makes much sense. $\endgroup$ – naught101 Apr 29 '14 at 1:16

These are visco-elastic oscillations that cause virtually no permanent deformation.

Following the Tohoku 2011 earthquake, this gravimeter in Metsähovi, Finland, measured a radial oscillation mode amplitude of 0.06 mm. The Earth's radius is 6371 km. So the resulting strains would be extremely small.

All but the lowest radial mode decays after a few days because the energy of the oscillations gets converted to heat by dissipative processes.


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