From the primitive age man has always known and feared earthquakes. We know about the large scale devastations they caused. Do you know who first invented a device for registering and detecting the intensity the earthquakes?
He was Chang Heng of China. In 132 A.D. the device for registering seismic activity was invented by him. The device had a number of metal balls around the rim of an urn. It was arranged in such a way that an earth tremor would disturb a central column, operating a mechanism that dropped one of its ball into a metal holder causing a noise. The direction of the earthquake could be worked out by seeing the balls that fell and that did not.
From this primitive device the modern sensitive seismographs evolved and a science has grown up with them known as the seismology or study of earthquakes. The Greek word Seimos means “a shaking”.
Within the past hundred years there have been many advances in the design of the device called “Seismographer”. Seismographers give a record of movement and waves of the earth’s crust at their location. There is now seismic recording equipment fixed in every country — making continuous recordings. A heavy inert weight is suspended in the equipment by a spring and attached to this is a fixed pen that is in contact with paper on a rotating drum. During earthquake the instrument’s frame and the drum move, causing the pen to record a zigzag line on the paper. The pen does not move.
These lines indicated the intensity and location of the earthquake. In modern observatories, at least two or three seismographers are installed. Each one is meant for monitoring the horizontal and vertical movements of earthquakes to measure and locate the exact centre of earthquake. It has not possible yet to design a seismograph to measure faithfully the movement of earth’s crust in every direction at once in response to seismic waves. However, it seems possible that earthquakes may soon be within man’s control to some extent.