NATURAL PHENOMENA

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NATURAL PHENOMENA: 

NATURAL PHENOMENA

CONTENT: 

CONTENT SESMIC WAVES TYPES OF SESMIC WAVES RICTHER SCALE EARTHQUAKE HARZARDS PROTECTION AGAINST EARTHQUAKES

SEISMIC WAVES: 

SEISMIC WAVES Seismic waves are generated by an earthquake shock. Each type of wave travels at a different speed as it moves through the earth. Waves move through the earth causing the particles making up rock to move also. The focus of an earthquake is the point in the Earth's interior where stress is released and rocks move. Waves move outward away from this area. .

TYPES OF SEISMIC WAVES: 

TYPES OF SEISMIC WAVES Primary waves are the first waves to arrive at a seismograph station. Are the fastest forms of wave, sometimes called compression waves. Can move through both liquids and solids. These waves cause rock particles to move back and forth in the same direction as the wave is traveling. Secondary waves arrive after the primary waves at the seismograph station. Can travel through solids but not liquids. Cause particles to move back and forth at right angles to the line of wave movement. Are called a sine wave.

Richter Scale : 

Richter Scale . The magnitude of most earthquakes is measured on the Richter scale , invented by Charles F. Richter in 1934. The Richter magnitude is calculated from the amplitude of the largest seismic wave recorded for the earthquake, no matter what type of wave was the strongest. The Richter magnitude scale can be used to desribe earthquakes so small that they are expressed in negative numbers. The scale also has no upper limit, so it can describe earthquakes of unimaginable and (so far) unexperienced intensity, such as magnitude 10.0 and beyond. .

Earthquake Hazards : 

Earthquake Hazards The first main earthquake hazard (danger) is the effect of ground shaking . Buildings can be damaged by the shaking itself or by the ground beneath them settling to a different level than it was before the earthquake ( subsidence ). These buildings in Japan toppled when the soil underwent liquefaction. Buildings can even sink into the ground if soil liquefaction occurs.. When the water and soil are mixed, the ground becomes very soft and acts similar to quicksand. Liquefaction is a hazard in areas that have groundwater near the surface and sandy soil.

The second main earthquake hazard is ground displacement (ground movement) along a fault. If a structure (a building, road, etc.) is built across a fault, the ground displacement during an earthquake could seriously damage or rip apart that structure.

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The third main hazard is flooding . An earthquake can rupture (break) dams or levees along a river. The water from the river or the reservoir would then flood the area, damaging buildings and maybe sweeping away or drowning people.

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The fourth main earthquake hazard is fire . These fires can be started by broken gas lines and power lines, or tipped over wood or coal stoves. They can be a serious problem, especially if the water lines that feed the fire hydrants are broken, too. For example, after the Great San Francisco Earthquake in 1906, the city burned for three days. Most of the city was destroyed and 250,000 people were left homeless.

HOW TO PROTECT AGAINST EARTHQUAKES: 

HOW TO PROTECT AGAINST EARTHQUAKES 1 .) If an earthquake is occurring the most important thing to do is to DROP and COVER. Drop and cover means to fall on to the floor and get under something for protection. During an earthquake, if you are indoors, it is very important to stay calm and take cover under a heavy object. 2.) If you are outdoors, stay as far away from buildings as possible. 3.) Stay away from glass or anything that could fall. 4.) If you are in a crowded area, do not even consider running for the nearest exit. Everyone will be doing that, and crowding will lead to even more injuries. Take cover under something heavy and stay away from things that could fall on you. It is also very important to remain as calm as possible. 5.) Be prepared for aftershocks after the initial earthquake has ended. Aftershocks are follow-up earthquakes. They are smaller than the first one, but still are very dangerous.

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