Earth vigor vibrations are vibrations that can occur after an earthquake because the Earth is in resonance.
With very powerful earthquakes with a magnitude greater than 7 on Richter's scale, the Earth as a whole can come in vibration. These vibrations are standing vibrations like in a string, and are also referred to as self-revolutions or "modes". The movement is good for vibrating a big bubble when floating through the air. Another comparison that is often made is that with a church bell. When clogged with the clamp, the whole clock is in vibration, after which the sound extends within ten seconds. When the Earth is "sounding" by an earthquake, it may take two days or more before the vibrations are stopped.
A church clock produces a ground tone and a whole range of overtones. That is the case with Earth too. However, the frequencies of Earth vibration are one million times as low as those of a clock. Earth's ground tone has a frequency of 0.000815 Hz, which corresponds to a period of 20 minutes and 27 seconds (1227 seconds). This fundamental tone is recorded occasionally by low-frequency seismometers. The overtones are recorded regularly, usually from the seventh or eighth over 10 minutes. Remarkably, the ground tone with the simplest movement, which is also called "breathing mode" (the Earth is bigger and smaller in size), does not have the lowest frequency. The lowest frequency of the Earth comes from the second overtones that the Earth turns on two imaginary axes alternately to a rugby ball. This football mode has a period of about 54 minutes. This period is influenced by the rotation of the Earth so that there are actually two tones with a small difference in period namely 54.7 and 53.1 minutes.
In addition to the Earth's movements described above in a direction perpendicular to the surface that give rise to the spheroidal modes, there are also property vibrations with a direction of motion along the surface; the toroidal modes. The lowest frequency vibration is one with the one hemisphere of the Earth turning to the left and the other to the right. It goes without saying that it is about very small movements in which the amplitude is not greater than a millionth millimeter.
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