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Where do Earthquakes Occur?

Learning about earthquakes? In today’s article we take a look at where and why these natural disasters happen. We’ll also discuss the effects of these earth-shaking tremors.

earthquakes-worldwide

To answer the question “Where are earthquakes common?” it’s probably best to start with why earthquakes happen. By understanding the reasons for them, we can easily identify where they happen most often.

Why do earthquakes happen?

An earthquake happens when two blocks of earth slide past each other. These blocks of earth are called plates and they cover the surface of our planet like massive puzzle pieces.

They are constantly moving, and when 2 plates rub together we get the effect that we call an earthquake. As the edges of these plates (called faults) become stuck together, the rest of the plates continue moving. This causes a huge amount of energy to be stored, which at some point needs to be released. When the plates finally become unstuck from each other, this stored up energy is all released at once. This release of energy is our earthquake.

Check out the map below to see how the plates are arranged worldwide. The map also shows in which directions the plates are currently moving.

worldwide tectonic plates

Fun Fact: The actually plates move so slowly that it is compared to the speed that our finger nails grow. However, as these chunks of land are so enormous they carry a great deal of power.


Where do earthquakes occur most often?

As we found out in the last section, earthquakes happen when plates meet and friction is stored up as they rub against each other. Therefore, earthquakes most commonly happen where these plates meet. We call this boundary that is invisible to our eyes, a fault line.

Most earthquakes happen along the fault line that separates the Pacific plate from its neighbors. Check out the picture below that clearly illustrates the areas most at risk from earthquakes (colored red). They outline the edges of the Pacific plate.

pacific ring of fire

This zone where earthquakes are most common is called the Ring of Fire. Approximately 90% of all earthquakes happen along this fault line, and it has 75% of the world’s active volcanoes in close proximity to it (volcanoes are created by the friction where plates meet too).

The part that covers the west coast of the U.S. is called the San Andreas fault. It is one of the most active parts of the Ring of Fire. It marks where the North American plate meets the Pacific plate and is 1,287 km long and 16km deep. It was the cause of the San Francisco earthquake of 1906, where around 3,000 people died as a result of fires. It is though that around 80% of the city was destroyed by the 7.9 strength earthquake.

The Ring of Fire was also responsible for an earthquake causing 70,000 deaths in Peru in 1970, and one causing $1,000,000,000 (one billion) worth of damage in California in 1971 (source).

Aside from the Ring of Fire, a section of belt called the Alpide, has also proven to be devastating. Around 5-6% of the world’s earthquakes occur here. Starting in Indonesia (Java) it passes through Sumatra, the Himalayas, the Mediterranean and ends in the Atlantic Ocean. It is thought that 17% of the largest and most destructive earthquakes occur here. Earthquakes around magnitude 7 were frequent in the late 60’s and early 70’s.

earthquake-destruction

Where do most of the earthquakes occur in the United States?

Researchers at the University of Nevada actually researched and compiled a list of the U.S. states that are most frequently affected by strong earthquakes. Their research concerns the strongest earthquakes recorded each year, based on accounts from 1568 to 1989 and seismological data from 1898 to 2005.

This is what they found:

  1. Alaska (6.70)
  2. California (6.02)
  3. Nevada (5.11)
  4. Hawaii (5.00)
  5. Washington (4.97)
  6. Wyoming (4.67)
  7. Idaho (4.57)
  8. Montana (4.47)
  9. Utah (4.29)
  10. Oregon (4.24)

Which country has the most earthquakes in the world?

This one is really hard to answer definitively, but Japan and Indonesia are definitely the two countries that experience the most earthquakes. Japan records the most official earthquakes (around 10% of the world’s volcanic activity resides here), but it is actually thought that Indonesia experiences more. The lack of seismic instruments to measure the earthquake activity, means Indonesia doesn’t have as many official earthquakes.

The countries that experience the most earthquakes per unit area Fiji, Tonga, and Indonesia.

earthquake-effects


Effects of Earthquakes

Earthquakes have far reaching and devastating effects. The impacts that earthquakes have are classified in 3 ways:

  • Social impacts – the effect on local people
    • Short term
      • Injury and death
      • Lack of power/electricity
      • Communication links broken
      • Destruction of homes and businesses
      • Disruption of food and water supplies (contamination, shortage etc.)
      • Transport links damaged (roads, rail-tracks, airports etc.)
    • Long term
      • Disease and sickness
      • Homes and businesses lost
      • Possible refugee camps
  • Economic impacts – the effect on the wealth of the local area
    • Short term
      • Loss of income (business destroyed)
      • Looting of shops
      • Trade is difficult (due to broken transportation and communication links)
    • Long term
      • Loss of property
      • Rebuilding is expensive
      • Local investment is focused on repairs rather than economic growth
      • Loss of income
  • Environmental impacts – the effect on the landscape
    • Short term
      • Buildings destroyed
      • Fires
      • Damage to natural areas like woodland
      • Landslides
      • Tsunamis
      • Flooding
    • Long term
      • Loss of historic and important landmarks

The consequences that an earthquake brings are also grouped as primary and secondary effects.

  • Primary effects – these are caused directly by the earthquake moving the ground. Examples of these are buildings toppling and damage to roads.
  • Secondary effects – these are caused by the primary effects. Examples of these are tsunamis and fires.

Cool Earthquake Facts

Here are some amazing facts to surprise your friends with.

  • The biggest ever recorded earthquake measured 9.5 on the Richter magnitude scale. It occurred in Chile in 1960.
  • The biggest ever earthquake recorded in the U.S. measured 9.2 and hit Prince William Sound in Alaska in 1964.
  • Over the past 3 million years, the average speed of movement of the San Andreas fault is 2 inches per year. Scientists project that Los Angeles and San Francisco will be next to each other in 15 million years.
  • The deadliest earthquake ever was thought to have happened in central China in 1556. An estimated 830,000 people are thought to have died. (source)

That’s all for today’s post on earthquakes. We’d love it if you’d follow us on social media. We post amazing facts daily that will blow your mind! Just click on the link on the right to ‘Like’ us on Facebook.

As ever, we’d love to hear of any interesting facts we’ve missed out. Be sure to drop us a comment in the box below.

Check out our latest post on weird animals.


Extra Image Sources:

By USGS [Public domain], via Wikimedia Commons

By Gringer (talk) 23:52, 10 February 2009 (UTC) (vector data from [1]) [Public domain], via Wikimedia Commons

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