Earthquake: what is an earthquake?

Earthquakes, or earthquakes, strike the globe daily. Presentation of a usual phenomenon, but always fascinating.

What is an earthquake?

An earthquake is a jolt due to a sudden release of energy accumulated in the subsoil. A rock movement then generates vibrations that propagate in the form of seismic wave trains.

There are four categories of earthquakes : tectonic earthquakes that owe their energy to the movement of the earth's plates, earthquakes of volcanic origin , earthquakes of polar origin due to ice movements, and earthquakes due to certain human activities such as dams, mining, or explosions.

The earthquakes are not exceptional ! There are even more each day ... but most are not felt by humans. Approximately one hundred thousand earthquakes are recorded each year on the planet.

The power of an earthquake is quantified by its magnitude , measured from 0 to 10 on the Richter scale. This one gets its name from its inventor, American seismologist Charles Francis Richter .

The most powerful earthquake of all time

The Valdivia earthquake , with a magnitude of 9.52, is the most powerful ever recorded. It took place on May 22, 1960. Its epicenter was located in southern Chile , near the town of Lumaco, 570 kilometers south of Santiago.

This earthquake was caused by a slippage of plates that displaced the ocean floor. This caused a tsunami that immediately devastated the Chilean coast before crossing the entire Pacific Ocean to the shores of Hawaii, Japan, New Zealand, Samoa, the Philippines and the Marquesas. More information about Santa Monica soft story

The city of Valdivia and its surroundings have been totally destroyed . In all, more than 30,000 people died in this earthquake.

The deadliest earthquake in history

The earthquake in Shaanxi , a Chinese province, was the deadliest in history. It took place in 1556 and resulted in the deaths of about 830,000 people.

Its epicenter was located in the Wei River Valley, near the cities of Huaxian, Weinan and Huayin. In these three cities, all the buildings and houses, often troglodytes, were destroyed. More than half of the population was killed. In some places, the earth opened , revealing crevasses of more than 20 meters. This earthquake, estimated at 8 on the Richter scale, has done damage for more than 800 km around.

Taiwan equips to detect earthquakes and tsunamis in advance

Taiwan - According to an AFP press release, the Taiwan authorities have just put in place an underwater seismic monitoring system designed to prevent, as far as possible, the devastating effects of future tsunamis.

Seismographs, pressure gauges and microphones placed at the bottom of the ocean, all connected to the town of Toucheng (north-east of the island) by a 45 km submarine cable, which sends in real time information on seismic activity: Taiwan has set up - for the first time - a high-tech monitoring of earthquakes off its coasts. The system was designed by the Japanese firm NEC Corp.

The goal: to gain precious moments in the event of a natural disaster. " This system gives us a clear idea of ​​what is happening. (...) We will gain an average of 10 seconds for earthquake alerts on the east side, and 10 minutes for a tsunami warning ," he said. Kuo Kai-wen, director of the seismological center.

An investment of $ 14.16 million is justified by the fact that Taiwan, straddling two tectonic plates, is particularly exposed to earthquakes, especially in the east (70% of earthquakes), where the Detectors: In September 1999, a magnitude 7.6 earthquake killed 2,400 people.

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