Hi "Yuri Markov" on your question of Earth's resonant frequency...in a book I read years ago(Tesla,man out of time by Margeritt Chenny) as I remember It was one hour and 50 min. He found this out by blasting a stick of T.N.T and then listening to the Earth's return stroke...He had said with more of the same at the same place at the correct stroke time it would be possible to split the earth... Denis Despins KC6TRW