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Sunday, 23 September 2012

Tuned pendulum

This web page  http://www.chcp.org/seismo.html describes the mechanism inside the ancient first seismometer (see this post) of the first century AD.
From seismo.html: "Our seismometer is intended as a demonstrator. The visitor shakes the table to simulate an earthquake. Our pendulum is "tuned" to this input. The crust of the earth absorbs the high frequency content of a quake, the signal from a distant earthquake is in the sub-audio range. In order to detect actual earthquakes the pendulum would need to be several feet in length."