Nikola Tesla's Earthquake Machine

Engineer Nikola Tesla is today famous for his work on electricity and energy. The alternating current electrical system, on which our modern civilization runs, is mostly his invention.  He was a brilliant thinker, but also with very eccentric ideas, including a belief in aliens. Maybe the more enigmatic parts of his personality make him such an interesting subject for conspiracists. Tesla is credited to have worked on unknown energy-sources, UFOs, caused the Tunguska explosion by a death-ray, and even worked on an earthquake-generator. 
In 1896 Tesla was working on waves and resonance to be used for energy transfer. The idea was to create a mechanical oscillator, able to create various frequencies, until matching the resonance frequency of the desired object. In 1897 the device was ready and in 1898 he supposedly managed to oscillate his laboratory at 48 E. Houston St., New York, enough, that alarmed neighbors called the police and ambulance, fearing an earthquake happening. Tesla later explained this principle to reporter Allan L. Besnson, who published in February 1912 an article about Tesla's resonator in The World Today magazine:

'He put his little vibrator in his coat-pocket and went out to hunt a half-erected steel building. Down in the Wall Street district, he found one, ten stories of steel framework without a brick or a stone laid around it. He clamped the vibrator to one of the beams, and fussed with the adjustment until he got it.

Tesla said finally the structure began to creak and weave and the steel-workers came to the ground panic-stricken, believing that there had been an earthquake. Police was called out. Tesla put the vibrator in his pocket and went away. Ten minutes more and he could have laid the building in the street. And, with the same vibrator, he could have dropped the Brooklyn Bridge into the East River in less than an hour.'

Tesla's steam-powered electric generator or oscillator. The device was intended to produce electric energy but could be also modified to generate mechanical vibrations.

Tesla imagined using the waves generated by his device for more peaceful applications, like to transport energy inside Earth. One device would transform electricity into vibrations and send it into Earth, another device would pick up the vibrations and transform the waves back into electricity, to be used locally. In fact, so Tesla, the device, consisting of a piston vibrating in a cylinder, was already powerful enough to vibrate an entire building. Just one precaution was necessary, if powerful enough, so Tesla, his machine could make resonate earth, causing even earthquakes. However, the 'telegeodynamics' system never managed to get beyond the prototype, even if Tesla got a patent on his design. Still, in the 1930s, Tesla imagined using smaller devices to relieve stress from Earth, so to prevent earthquakes, or use the vibrations to prospect the underground. Modern seismology, in fact, uses vibrations, generated by controlled explosions or mechanical pistons, as sort of underground echo sounding, to prospect. However, nobody still to this date possesses an earthquake machine...