<P> The first seismometer was made in China during the 2nd Century . The first Western description of the device comes from the French physicist and priest Jean de Hautefeuille in 1703 . </P> <P> The modern seismometer was developed in the 19th century . </P> <P> In AD 132, Zhang Heng of China's Han dynasty invented the first seismoscope (by the definition above), which was called Houfeng Didong Yi (translated as, "instrument for measuring the seasonal winds and the movements of the Earth"). The description we have, from the History of the Later Han Dynasty, says that it was a large bronze vessel, about 2 meters in diameter; at eight points around the top were dragon's heads holding bronze balls . When there was an earthquake, one of the mouths would open and drop its ball into a bronze toad at the base, making a sound and supposedly showing the direction of the earthquake . On at least one occasion, probably at the time of a large earthquake in Gansu in AD 143, the seismoscope indicated an earthquake even though one was not felt . The available text says that inside the vessel was a central column that could move along eight tracks; this is thought to refer to a pendulum, though it is not known exactly how this was linked to a mechanism that would open only one dragon's mouth . The first earthquake recorded by this seismoscope was supposedly "somewhere in the east ." Days later, a rider from the east reported this earthquake . </P> <P> An early special - purpose seismometer consisted of a large, stationary pendulum, with a stylus on the bottom . As the earth started to move, the heavy mass of the pendulum had the inertia to stay still within the frame . The result is that the stylus scratched a pattern corresponding with the Earth's movement . This type of strong - motion seismometer recorded upon a smoked glass (glass with carbon soot). While not sensitive enough to detect distant earthquakes, this instrument could indicate the direction of the pressure waves and thus help find the epicenter of a local quake . Such instruments were useful in the analysis of the 1906 San Francisco earthquake . Further analysis was performed in the 1980s, using these early recordings, enabling a more precise determination of the initial fault break location in Marin county and its subsequent progression, mostly to the south . </P>

Who developed the first procedure used to measure the local size of an earthquake