Earthquakes can be caused by erupting volcanos, meteor impacts or even from underground explosions such as a result of nuclear testing. Most, however are naturally occurring, caused by movements of the earths tectonic plates.
Where the Earth's tectonic plates meet (called "faults") they shift and rub against each other generating huge amounts of energy that when released results in seismic waves. These seismic waves are what we know as earthquakes. The San Andreas fault extends over 650 miles, making California one of the most active earthquake areas in the world.
Different cultures have various legends regarding the cause of earthquakes. One Indian legend has seven serpents sharing the task of holding up the Earth; when one finishes its turn and another moves into place, people will feel a jolt.
Reports tell of animals apparently foretelling earthquakes hours or even days before occurring. Villagers in Bang Koey, Thailand, followed a herd of stampeding buffalo from the beach to higher ground minutes before the tsunami struck.
The relatively new scientific study of earthquakes is called seismology. Before the eighteenth century occurrences were recorded as fanciful theories as to why they occurred - one being that they were caused by air rushing out of caverns deep inside the earth.
Earthquake predictions still cannot be pinpointed accurately within months or even years, but once the quake has ruptured seismologists can determine the magnitude within seconds.
A History Of Earthquakes Around The World
The US Geological Survey estimates that three million earthquakes, mostly undetectable, happen every year around the world. Thats one every 11 seconds!
Due to its high number of volcanos, Japans earth crust is one of the most unstable. This causes approximately 1,000 earthquakes each year. Most are mild and cause little or no destruction.
Another earthquake-prone area is San Francisco, where the 1906 earthquake killed 700 people and was felt 400 miles away in Los Angeles. One of the buildings to survive was A.P Hotalings Whiskey Warehouse. One local poet wrote:
If, as some say, God spanked the town for being frisky, why did he burn the churches down and save Hotalings Whiskey?
In April 2003, the Russian newspaper Pravda reported tremors in Iran measuring five on the Richter Scale. Russian seismologists believe they were caused by the bombing in Iraq with analysis showing that earthquakes can begin in seismologically active areas two to four weeks after bombings take place.
The Boxing Day tsunami that devastated Thailand in 2004 was caused by a magnitude 9.3 earthquake under the Indian Ocean. The fault shook for at least eight minutes (as opposed to the typical 30 seconds) and Earths gravity balance was so altered that the North Pole shifted by an inch.
Earthquakes In the UK?
Scotland is Britain's earthquake hotspot, although most measure well below 2.5 on the Richter Scale. Wales has also seen its fare share of seismic activity and in 1984 a quake measuring 5.4 on the Richter Scale was recorded there.
On average, it is thought that an earthquake hits the British Isles every four days, but quakes above five on the Richter scale are very rare. Luckily, British natural disasters are rare.
Experts believe global warming and the resulting rise in sea levels could cause Earths tectonic plates to shift, seeing an increase in the number of earthquakes.
If you dont want the earth to move, it's probably best go green!
- There is one earthquake every 11 seconds.
- San Andreas fault extends over 650 miles.
- Some reports tell of animals apparently sensing an oncoming earthquake.
- Bombing in Iraq may have caused an earthquake in Iran.