Who Designed the First Modern Seismograph?
Seismic waves are the vibrations from earthquakes that travel through the Earth; they are recorded on instruments called seismographs. Seismographs record a zigzag trace that shows the varying amplitude of ground oscillations beneath the instrument.
Sensitive seismographs, which greatly magnify these ground motions, can detect strong earthquakes from sources anywhere in the world. The time, location and magnitude of an earthquake can be determined from the data recorded by seismograph stations. The sensor part of a seismograph is referred to as the seismometer, the graph capability was added as a later invention.
John Milne was the English seismologist and geologist who invented the first modern seismograph and promoted the building of seismological stations. In 1880, Sir James Alfred Ewing, Thomas Gray and John Milne, all British scientists working in Japan, began to study earthquakes. They founded the Seismological Society of Japan and the society funded the invention of seismographs. Milne invented the horizontal pendulum seismograph in 1880.
The horizontal pendulum seismograph was improved after World War II with the Press-Ewing seismograph, developed in the United States for recording long-period waves. It is widely used throughout the world today. The Press-Ewing seismograph uses a Milne pendulum, but the pivot supporting the pendulum is replaced by an elastic wire to avoid friction.
Around 132 A.D., a Chinese scientist Chang Heng, invented the first seismoscope, an instrument that could register the occurrence of an earthquake. Heng’s invention, ‘the dragon jar’ was a cylindrical jar with eight dragon heads arranged around its brim.
Each dragon head had a ball in its mouth. Around the foot of the jar were eight frogs, each directly beneath a dragon head. During an earthquake, a ball dropped from a dragon’s mouth, and was caught by the frog.