During the Eastern Han Dynasty, earthquakes were relatively frequent. In the 30 years from 96 to 125 AD, there were 23 relatively strong earthquakes, sometimes as large as dozens of counties.

In 132, scientist and litterateur Zhang Heng invented and manufactured the world's first instrument for determining the direction of earthquakes-the wind and earth motion instrument. Zhang Heng placed the wind seismograph in the capital Luoyang. At first, civil and military officials of the Manchu Dynasty did not believe that this seismograph could measure the direction of an earthquake.

Coincidentally, on March 1, 138 (the third day of February, the third year of the Han Yonghe,{sys:(year(now)-138)} years ago), suddenly the steel ball of the seismograph facing northwest fell down and fell into the mouth of the toad under the instrument. However, no one in Luoyang felt the earthquake. A few days later, people from Longxi Post rushed to the capital day and night to report the Longxi earthquake and the landslide in the second county (magnitude of approximately 6.5). Longxi is just northwest of Luoyang.

In the face of facts, everyone has to admit the effectiveness of the wind seismograph and admire Zhang Heng's invention.

More than 1700 years later, European talents created the "first" seismograph.