21 -Amazing Facts about Earthquakes

Earthquakes

Amazing Facts about Earthquakes

A natural part of our planet’s workings, earthquakes can be terrifying and destructive events. Some trigger powerful ocean waves called tsunamis. Earth’s outer shell is made up of huge slabs called tectonic plates.

These plates are constantly moving, and push past each other with hard, jerky movements. In some places, the opposing masses of rock become locked together by friction.

In these periods, there is a gradual buildup of strain in the locked-up area. Eventually, the pressure becomes so high that there is a sudden shift between the blocks of rock, or a massive break, usually on or near lines on the Earth’s surface called faults.

As this happens, energy is released in the form of powerful shock waves, or vibrations, causing an earthquake. When an earthquake happens under the seafloor, it can create a tsunami.

Most earthquakes occur on the plate boundaries of Earth’s crust, where the plates are moving relative to one another. This movement may cause just minor tremors, but if the plates lock together, the strain builds up until something snaps. It is this sudden release of tension that causes a big, destructive earthquake.

EARTHQUAKE ZONES

{1} In the 1960s, the United States used a network of seismometers (instruments that record motions in the ground) to monitor nuclear bomb tests. The instruments also recorded all the earthquakes worldwide, and revealed that most of them (shown in red below) occur in narrow bands along the tectonic plate boundaries.

{2} During the 1964 Alaska earthquake, the Pacific floor slid 66 ft (20 m) beneath Alaska in just three minutes, and lifted an old shipwreck out of the water.

{3} earthquake waves are picked up and recorded using seismometers or seismographs. They are often measured on the Richter scale of magnitude. Each increase in number represents ten times the shaking force, so a category 7 earthquake is ten times as powerful as a category 6.

{4} The earthquake that caused the 2011 tsunami in Japan measured 9.0 on this scale.

{5} An earthquake measuring 8.5 on the Richter scale caused this building in Sichuan, China, to collapse in 2008.

{6} There are roughly half a million earthquakes every year. The biggest earthquake recorded so far hit 9.5 on the Richter scale. A deadly quake killed around 316,000 people in Haiti in 2010. The widespread damage badly hampered rescue efforts.

{7} The largest ever recorded earthquake occurred in Chile on 22 May 1960. It was an earthquake of 9.5 magnitude intensity.

{8} In ancient Greece , people believed that the earthquake was caused by the sea god Poseidon . They said that when the gods get angry , they hit the ground with their trident , which makes the earth tremble .

{9} The most dangerous landslide caused by the earthquake was in 1920 in Kansas province , China . Nearly 2 lakh people were killed due to the landslide .

{10} On 31 January 1906,an earthquake of 8.8 struck Ecuador . This caused a tsunami there This natural disaster put at least 500 people to sleep here.

{11} The earliest known seismoscope was invented by Chinese philosopher Chang Hêng in 132. It didn’t actually record ground movements, but simply indicated that an earthquake had hit. The cylindrical vessel had eight dragon heads around the top, facing the eight principal directions of the compass, each with an open-mouthed toad underneath it. Inside the mouth of each dragon was a ball that would drop into the mouth of the toad below when an earthquake occurred.

{12} The direction of the shaking could be determined by which dragon released its ball. It is not known what was inside the vessel, but it is thought that some kind of pendulum was used to sense the earthquake and activate the ball in the dragon’s mouth.

{13} The instrument reportedly detected a 650-kilometre (373-mile)-distant earthquake which was not felt by people at the location of the seismoscope.

{14} The plate boundaries around the Pacific Ocean make up what is known as the Ring of Fire, an area where 90 per cent of the world’s earthquakes occur.

Measuring the magnitude of earthquakes using US seismologist Charles F Richter’s system

{15} 0-2.9 There are more than 1 million micro earthquakes a year but they are not felt by people.

{16} 3.0-3.9 Minor earthquakes are felt by many people but cause no damage – there are as many as 100,000 of these a year.

{17} 4.0-4.9 Felt by all, light earthquakes occur up to 15,000 times a year and cause minor breakages.

{18} 5.0-5.9 A moderate earthquake causes some damage to weak structures. There are around 1,000 of them a year.

{19} 6.0-6.9 Over 100 strong earthquakes happen each year, causing moderate damage in populated areas.

{20} 7.0-7.9 A loss of life and serious damage over large areas are the result of major earthquakes that happen around ten times a year.

{21} 8.0 & higher There are fewer than three earthquakes classed as ‘great’ each year, but they cause severe destruction and loss of life over large areas.

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