Earthquakes involve the powerful movement of rocks in the Earth’s crust. The rapid release of energy creates seismic waves that travel through the earth.
Scientists use the different speeds of seismic waves to locate the epicentre (the point on the surface directly above where the earthquake originated) of earthquakes.
Seismometers are used to measure the magnitude of earthquakes. You are unlikely to feel a magnitude 3 earthquake but a magnitude 6 earthquake could potentially cause large damage.
The damage caused by earthquakes also depends on their depth and fault type.
The earthquake that hit the Tohoku region of Japan on March 11, 2011, had a magnitude of 9.0 and killed over 15000 people.
The destruction caused by the Tohoku earthquake was made much worse by powerful tsunamis that were triggered due to the earthquake’s epicentre being located offshore. More tsunami facts.
The 2004 earthquake that occurred in the Indian Ocean near Sumatra, Indonesia triggered a series of tsunamis that killed over 200000 people in 14 countries.
The February 2011 earthquake in Christchurch, New Zealand followed nearly 6 months after a magnitude 7.1 earthquake shook the region. The earthquake killed 181 people and significantly damaged the central city. The economic damage caused by the earthquake and aftershocks is estimated to be around $15 billion (NZ$).
An earthquake that hit Haiti in January 2010 with a magnitude of 7.0 killed over 200,000 people according to Haitian sources.
The most powerful earthquake ever recorded on Earth was in Valdivia, Chile. Occurring in 1960, it had a magnitude of 9.5.
It is important in earthquake prone countries such as Japan to build houses and buildings that react well to earthquakes. Good engineering practices can help stop buildings collapsing under the stress of large earthquakes.
A massive 8.8 earthquake in Chile moved the city of Concepción 10 feet to the west on February 27, 2010. This quake also shortened Earth's day and slightly changed the rotation of the planet.
The deadliest earthquake known hit Shansi, China on January 23, 1556. An estimated 830,000 people died.
Earthquakes kill approximately 8,000 people each year and have caused an estimated 13 million deaths in the past 4,000 years.
The moment magnitude scale (MMS) replaced the 1930s-era Richter scale in the 1970s as the method of measuring the size of earthquakes in terms of energy released.
The Indian Ocean earthquake in 2004 generated enough energy to power all the homes and businesses in the United States for three days.
Earth has been more seismologically active in the past 15 years or so, says Stephen Gao, a geophysicist at Missouri University of Science and Technology. Not all seismologist agree, however.
2. San Francisco is moving toward Los Angeles at the rate of about 2 inches per year — the same pace as the growth of your fingernails as the two sides of the San Andreas fault slip past one another. The cities will meet in several million years. However, this north-south movement also means that despite fears, California won't fall into the sea.
3. March is not earthquake month, despite what some people believe. True, on March 28, 1964, Prince William Sound, Alaska, experienced a 9.2 magnitude event — one of the biggest ever. It killed 125 people and caused $311 million in property damages. And on March 9, 1957, the Andreanof Islands, Alaska, felt a 9.1 temblor. But the next three biggest U.S. earthquakes occurred in February, November, and December. The devastating major earthquake in Chile of 2010 struck on Feb. 27. And the huge 9.3 temblor that spawned the devastating Indian Ocean tsunami in 2004 occurred on Dec. 26.
4. There are about 500,000 earthquakes a year around the world, as detected by sensitive instruments. About 100,000 of those can be felt, and 100 or so cause damage each year. Each year the southern California area alone experiences about 10,000 earthquakes, most of them not felt by people.
5. The sun and moon cause tremors. It's long been known that they create tides in the planet's crust, very minor versions of ocean tides. Now researchers say the tug of the sun and moon on the San Andreas Fault stimulates tremors deep underground.
6. A city in Chile moved 10 feet in the massive 8.8 magnitude earthquake Feb. 27, 2010. The rip in Earth's crust shifted the city of Concepción that much to the west. The quake is also thought to have changed the planet's rotation slightly and shortened Earth's day.
7. There's no such thing as "earthquake weather." Statistically, there is an equal distribution of earthquakes in cold weather, hot weather, rainy weather, and so on, according to the U.S. Geological Survey. Scientists say there is no physical way that weather could affect the forces several miles beneath the surface of the earth where quakes originate. The changes in barometric pressure in the atmosphere are very small compared to the forces in the crust, and the effect of the barometric pressure does not reach beneath the soil.
8. Earth's bulge was trimmed a little by the 2004 Indonesian earthquake, the 9.0+ temblor that generated the deadly tsunami on Dec. 26 that year. Earth's midsection bulges in relation to the measurement from pole-to-pole, and the catastrophic land displacement caused a small reduction in the bulge, making the planet more round.
9. The Pacific Ring of Fire is the most geologically active region of Earth. It circles the Pacific Ocean, touching the coasts North and South America, Japan, China and Russia. It's where the majority of Earth's major quakes occur as major plate boundaries collide.
10. Oil extraction can cause minor earthquakes. These are not the quakes you read about. Rather, because oil generally is found in soft and squishy sediment, when oil is removed other rock moves in to fill the void, creating "mini-seismic events" that are not noticeable to humans.
11. The largest earthquake ever recorded was a magnitude 9.5 in Chile on May 22, 1960.
12. Quakes on one side of Earth can shake the other side. Seismologists studying the massive 2004 earthquake that triggered killer tsunamis throughout the Indian Ocean found that the quake had weakened at least a portion of California's famed San Andreas Fault. The Chilean quake of 1960 shook the entire Earth for many days, a phenomenon called oscillation that was measured by seismic stations around the planet.
13. The deadliest earthquake ever struck January 23, 1556 in Shansi, China. Some 830,000 are estimated to have died.