The earliest known seismoscope, a device used to detect earthquakes, was invented in China in 132. The device consisted of eight metal dragons mounted around a cylinder, each with a bronze ball in its mouth. When a slight tremor struck, a ball would fall out of one of the dragons’ mouths into a waiting receptacle. The direction of the tremor could be judged based on which dragon had released its ball. The device is said to have detected an earthquake 400 miles away. (Read about the first seismoscope and other ancient inventions you thought were modern.)

Although this early device could determine whether an earthquake had happened in its vicinity, it couldn’t measure the strength of the quake. Modern seismographs, which record the motion of the ground during earthquakes, came into use in 1890. But because earthquakes are strongest at their epicenter and weaker further away, readings of the same earthquake differ depending on the location of the seismograph. Nowadays, multi-station seismographic networks are used to pinpoint the center and determine the magnitude of a quake.

24/7 Tempo has determined the 20 most powerful earthquakes ever recorded by reviewing data from The United States Geological Survey (USGS). Magnitudes are measured on the Moment Magnitude scale (Mw). The earthquakes considered occurred in the 20th century and after, as any occurring before this time were not able to be standardized to the current scale. For earthquakes that occurred before 1935, when the (now outdated) Richter Scale was developed, magnitude measurements are estimates based on historical seismogram readings.

Click here to see the most powerful earthquakes ever recorded

A few areas of high tectonic activity are responsible for many of the largest earthquakes of all time. About 80% of earthquakes occur in what is called the “Ring of Fire” – a zone around the Pacific Ocean where the Pacific tectonic plate is being subverted (or pushed under) the surrounding plates. Unfortunately, this means that some countries and areas, including Chile, Indonesia, Japan, the Kamchatka Peninsula of Russia, and the Aleutian Islands of Alaska have experienced numerous devastating earthquakes throughout their histories. (Here are ancient civilizations destroyed by natural disasters.)

Earthquakes can destroy whole towns and displace residents – sometimes permanently – as a result of landslides, flooding, and soil liquefaction. They cause millions and sometimes billions of dollars in damage. More often than not, however, the damage caused by an actual quake is minor compared to the death and destruction caused by the massive tsunamis that can form as a result of underwater quakes.