The oldest functioning seismograph is known as the Zhang Heng seismograph, invented in China in 132 AD. It is also known as the "earthquake weathercock" due to its shape.
The Zhang Heng seismograph consists of a large bronze vessel with eight dragon heads attached to the sides. Inside the vessel, there is a central pendulum suspended by a series of levers and gears. When an earthquake occurs, the pendulum is triggered to swing, causing one of the dragon's heads to drop a ball into the mouth of a toad-shaped container below. This indicates the direction of the earthquake's epicenter.
The Zhang Heng seismograph is considered important because it was the first known instrument used to detect and measure earthquakes. It was also accurate in its readings and provided a visual representation of the direction and intensity of an earthquake.
The Zhang Heng seismograph is still functioning today due to its well-preserved state and the fact that it has been replicated and tested by scientists. It has been proven to accurately detect earthquakes and its design has been studied and replicated in modern seismographs.
Since the invention of the Zhang Heng seismograph, there have been numerous advancements in seismograph technology. Modern seismographs use electronic sensors and computers to detect and record earthquakes, providing more detailed and accurate data. They also have the ability to detect and measure different types of seismic waves, providing a better understanding of earthquake dynamics.