In 132 AD, Zhang Heng of the Eastern Han Dynasty invented the Seismograph, which can be said to be the world's first instrument for recording earthquakes. The appearance of the Seismograph showed that at that time, the Chinese people had already realized that an earthquake was a kind of vibration transmitted from a distant place, which was a remarkable progress in ideological understanding. In 138 AD, an earthquake occurred in Longxi. People in Luoyang, thousands of miles away from the epicenter, were completely unaware of it, but the Seismograph detected an earthquake in the direction of Longxi. A few days later, the news of the Longxi earthquake reached Luoyang, and people found the Seismograph very amazing. At that time in China, the transmission of earthquake information relied on relay horses, so it often took a long time after an earthquake for people to receive the news.
Nowadays, when an earthquake occurs in a certain area, the modern seismographs set up around the area can quickly transmit the earthquake wave data to the data center via the network and start the calculation program. First, the computer quickly calculates the approximate location and magnitude of the earthquake, and then the seismologists conduct manual earthquake identification to improve the accuracy of the location. In this way, within a few minutes, the time, location, and magnitude of the earthquake can be measured. Compared with Zhang Heng's Seismograph, this is a great leap forward.
However, neither the Seismograph nor the earthquake detector is a prophet. They can only record the earthquake waves generated by the earthquake, but cannot predict the earthquake. That is to say, it is only after the earthquake generates earthquake waves that the earthquake detector can detect and record them. The earthquake detector obtains data after the earthquake, not before it. So far, humans have not been able to accurately predict earthquakes. However, earthquake prediction research cannot do without earthquake detectors. People need to use earthquake detectors to explore the mysteries of earthquake occurrence, and then hope to accurately predict earthquakes and reduce disasters in the future.