Thursday, January 12, 2012

The Earliest Measured Earthquake

One question about earthquakes gives me an excuse to provide a bit of fascinating history:

Hello...Can you please tell me if the first ever seismatic recording was on Earth or the Moon?
Thank you!  :)

The earliest measured earthquake occurred in China, and was detected using an elegant seismoscope invented by the Chinese philosopher/scientist Chang Heng around 132 A.D. I've seen a replica of this device, a bronze urn with eight downward-facing bronze dragons, each attached on the outside in the 8 cardinal directions. Each dragon holds a ball loosely in its mouth, and below each dragon's mouth, arrayed around the urn, there is a small ceramic cup. The idea is that the ball will pop out and fall out into the cup in the direction of the traveling earthquake (Raleigh) wave that rolls through the site hosting the seismoscope. If you travel in the opposite direction, you should eventually arrive at the epicenter. This simple device is immensely cool, and implies a marvelous observation-based understanding. It draws visiting school children to its glass display, in the US Geological Survey National Center lobby in Reston, VA, in droves. 

Prior to that instrument, earlier reported events were noted in Chinese literature -- one such event dates back to the Xia dynasty in 1831 B.C.

The first Moonquakes were detected by solar-panel-powered seismometers placed on the lunar surface by Apollo astronauts during their explorations on the Moon's surface (1969 to 1972).


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