Information on a naturally occurring hazard
Earthquakes and their impacts.
Richter Scale
Monday, May 23, 2011 / 3:04 AM ♫
| Richter scale no. | No. of earthquakes per year | Typical effects of this magnitude |
| < 3.4 | 800 000 | Detected only by seismometers |
| 3.5 - 4.2 | 30 000 | Just about noticeable indoors |
| 4.3 - 4.8 | 4 800 | Most people notice them, windows rattle. |
| 4.9 - 5.4 | 1400 | Everyone notices them, dishes may break, open doors swing. |
| 5.5 - 6.1 | 500 | Slight damage to buildings, plaster cracks, bricks fall. |
| 6.2 6.9 | 100 | Much damage to buildings: chimneys fall, houses move on foundations. |
| 7.0 - 7.3 | 15 | Serious damage: bridges twist, walls fracture, buildings may collapse. |
| 7.4 - 7.9 | 4 | Great damage, most buildings collapse. |
| > 8.0 | One every 5 to 10 years | Total damage, surface waves seen, objects thrown in the air. |
Labels: earthquake, table
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Historic Facts
It is estimated that there are 500,000 detectable earthquakes in the world each year. 100,000 of those can be felt, and 100 of them cause damage.
The largest recorded earthquake was a 9.5 quake in Chile in 1960.
Animals do appear to detect some earthquakes before they happen.
The Greek Philosopher, Aristotle, discovered that soft ground shakes more than the hard and rocky ground during an earthquake.
Seismic waves move at different speeds in different rocks.
On average, a magnitude 8 quake strikes somewhere every year and some 10,000 people die in earthquakes annually.
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What are Earthquakes
Earthquakes can be described basically as the Earth 'shuddering'. It is a burst of sudden
energy released from the Earth crust, resulting in seismic waves and after shocks. These vibrations run through the ground, and
depending on their level of energy they can cause absolute destruction to whole towns, or do very little or no damage at all.
The magnitude of the earth quake can be measured with a device called a seismometer. A recent post shows the Richter scale of how
earthquake are measured.
Richter Scale
Monday, May 23, 2011 / 3:04 AM ♫
| Richter scale no. | No. of earthquakes per year | Typical effects of this magnitude |
| < 3.4 | 800 000 | Detected only by seismometers |
| 3.5 - 4.2 | 30 000 | Just about noticeable indoors |
| 4.3 - 4.8 | 4 800 | Most people notice them, windows rattle. |
| 4.9 - 5.4 | 1400 | Everyone notices them, dishes may break, open doors swing. |
| 5.5 - 6.1 | 500 | Slight damage to buildings, plaster cracks, bricks fall. |
| 6.2 6.9 | 100 | Much damage to buildings: chimneys fall, houses move on foundations. |
| 7.0 - 7.3 | 15 | Serious damage: bridges twist, walls fracture, buildings may collapse. |
| 7.4 - 7.9 | 4 | Great damage, most buildings collapse. |
| > 8.0 | One every 5 to 10 years | Total damage, surface waves seen, objects thrown in the air. |
Labels: earthquake, table
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How and why Earthquakes form
Our Earth is made up of a solid inner core, liquid outer core, mantle and crust.
There are large tectonic plates that float around on the magma in the hot mantle, and when these plates drift and
bump into each other, they cause vibrations through the land sitting on top of them. When they crash, certain landforms
with be created, such as mountain ranges or simply the earth with tremor (depending on the size and force of the plate)
and the ground may crack open.
There is also another theory called the 'elastic rebound theory' which scientists say that the seismic waves that run
through out the Earth build up and cause stress on a existing weakness in the Earth. Eventually the strain is too much,
and the waves are released, seeming something along the image of a rubber band being pulled till snapping.
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Impacts
Environmentally
-They can cause volcanic eruptions
-Vegetation can be destroyed
-Landslides and aftershocks may occur
-Many in-ground animals and land creatures habitats can be ruined
-Trees and native plants ruined and damaged
Socially
-Business can be removed, resulting in unemployment
-Loss of lives of family, friends, communities
-Damage or loss of property
-Disruption of transportation and communication
-School buildings and educational places may be ruined
-Major food crops and farming areas may be damaged
Economically
-Money, time and resources are spent on preparation and warnings issued
-The bill of cleaning up rubble and damaged building when over can result in millions
-Losses in some form of agriculture
-May find people homeless with no structure remaining
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