the earthquake detector

The earthquake detector was created during the Han dynasty by the inventor Zhang Heng. Zhang Heng was an astronomer, mathematician, engineer, geographer and inventor who lived during the Han Dynasty (25 – 220 AD).

Heng's invention was used to determine the direction of the earthquake.

What did it look like?

• THe seismoscope was a giant bronze vase shaped object about 1.8 meters in diameter.
• 8 dragons were placed face-down along the outside of the vase, marking the primary compass directions.
• In each dragon's mouth was a small bronze ball.
• Beneath the dragons sat 8 bronze toads, with their mouths open to receive the balls.

How did it work?

• How the seismoscope exactly worked is still debated but this is how we think it worked.
• Inside the vase was a metal rod. When an earthquake struck, the rod hit the side of the vase causing a ball to drop from the dragon's mouth
• A ball fell from the dragon and into the frog's mouth in the direction of the earthquake
• People then knew where the earthquake had occured
• Aid could then be sent to the affected region

Impact on Modern times

• In 2005, scientists in Zengzhou, China (which was also Zhang's hometown) managed to replicate Zhang's seismoscope and used it to detect simulated earthquakes based on waves from four different real-life earthquakes in China and Vietnam.
• The earthquake detector detected all of them.
• In fact, the data gathered from the tests corresponded accurately with that gathered by modern-day seismometers!

THe seismoscope in action

• Heng decided to show his invention to the emperor. The seismoscope indicated that an earthquake happened west of Luoyang, the capital city.
• The seismoscope indicated that an earthquake happened west of Luoyang, the capital city.
• No one had felt a quake in Luoyang, so the alarm was ignored. However, a few days later, a messenger from west of Luoyang arrived in the city to report that his region had experienced an earthquake.
• The earthquake had occurred at the same time Zhang’s machine sounded the alarm. This city of Longxi, some 300 miles away, lay in ruins.

Key Facts

• Heng's detector was made 2000 thousand years before the first Western model
• It worked until the death of its inventor, but apparently the device was so complex only Zhang could keep up with its maintenance effectively.
• If this machine worked as well as well as it did 2000 years ago it would still be ahead of our time today.