Jun 23, 2001 06:56 PM
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An earthquake is a sudden motion or trembling in the Earth caused by the abrupt release of slowly accumulated strain. Most earthquakes occur along faults, or breaks, in the Earth’s crust. The San Andreas fault in California is the one that we’re all familiar with, but there are millions of faults all over the earth. The largest faults occur along the edges of the huge tectonic plates that comprise the Earth’s crust. Slowly and ponderously, the plates are traveling across the face of the planet, carrying us as passengers. Energy is stored up as the plates push, crush and grind against each other, and then suddenly released as an earthquake when the strength of the Earth is exceeded. For Example, * try slowly bending a plastic ruler or twig with one hand while you hold it firmly with the other. If you let go, there will be a sudden release of stored energy*, just as an earthquake. May be you’re thinking that you’re safe and sound in your region as it may be away from the nearest plate boundary. Well, that would be a big mistake!
Earthquakes can also be generated along much smaller faults, including in the middle of the plates. In fact, the recent devastating Gujarat Earthquake occurred in the middle of the Indian plate. Although the tremendous force of tectonic plates grinding against each other is responsible for many earthquakes, we humans can cause them as well. For example, nuclear bomb explosions produce small earthquakes and one of the ways in which nuclear test bans are verified is to monitor earthquake activity in different parts of the world. The impoundment of large surface water reservoirs is also known to cause earthquakes because the large volume of water exerts pressure on the Earth. Other earthquakes occur in the middle of the plates and are caused by the geophysical factors. Such factors include, but are not limited to, identified or unidentified faults(or “crust cracks” within the earth); the level of the water table; geological formations including soil and rock deposits over geological time; or the general stability of the soil and rock in the are. As the world gets more populous and richer, allowing a more built-up environment, higher buildings and all the infrastructure that supports our civilization, communications and the like, the risk of earthquakes goes up. The city of Kolkata is among the cities at risk, in addition to Islamabad, Los Angeles, Tokyo and Taipei, the capital of Taiwan.
Dangers from an Earthquake: The four greatest dangers that exist from an earthquake are the effects of the ground shaking, the effects of ground displacement, flooding, and fire. The greatest danger is the effects of the ground shaking. The actual “quaking” of the earth seldom causes death or injury. Most casualties result from the effects of the ground shaking, such as collapsing walls, falling glass, or falling objects during a quake. Other effects from the ground shaking include buildings damaged as the ground beneath them settles to different levels. If the earth is mixed with water, like ground water, then the ground becomes soft and the building may lean or even tip over. The second greatest danger is the effects of ground displacement. This includes landslides and mud slides, avalanches. Also, if a building was built across the fault, it could be seriously damaged or ripped apart. The third greatest danger from an earthquake is the flooding that may occur. This may be in the form of flash floods, the result of the breaking of a dam or river levee. Thefourth greatest danger is fire, usually started by broken gas and/or power lines. If the water mains are also broken, then putting out these fires becomes more difficult.
In countries where wood or coal is used a heating source, tipped over stoves can start a fire. Earthquakes are inevitable, but the damage from Earthquakes is not. By planning and practicing what to do if an Earthquake strikes, you and your family learn to react correctly and automatically when shaking begins.
Some of the Earthquake precautions include: Before Earthquake:- Check security of the building:- such as repairing deep plaster cracks in the ceiling, anchoring overhead lighting fixtures to the ceilings etc., Other measures such as…
a)Put shelves or showcases towards the wall
b)Place large & heavy objects on lower portion of showcases or shelves
c)Put breakable items such as glass items, pictures, mirrors in low closed cabinets.
d)Most importantly check & if required repair defective electrical wiring and leaky gas connections to avoid fire risk.
e)Secure a water heater by strapping it to the wall stud and bolting it to the floor.
f)Repair any crack in wall, ceilings or foundation. Get experts advice if required.
g)Identify safe places in each room like under sturdy furniture such as heavy desk or table that place must be away from where glass could shatter like windows, mirror, pictures or where heavy bookcases or other heavy furniture could fall over.
h)Locket safe places outdoor, away from buildings, trees, electric or telephone lines, flyovers or bridges. i)Keep following articles ready near hand… i.Flash lights and extra batteries ii.Portable battery operated radio and its batteries iii.First aid kit and medicines iv.Emergency food and water v.Cash and credit cards.
During the Earthquake:- This stage is the most important one.
Precautions:-If possible, try to run out side towards the safer grounds. If… Your are indoors… a)Take cover under heavy furniture or against an inside wall and hold on. The most dangerous thing to do is leave the covered place and run outside a falling building because objects can fall on you. So hold on to your safer place and better until ground stops shaking and it is safe to go outside. Remember aftershock might come. If many people are in room, try to give courage to them and make them calm specially the children. If the lights go out, use a battery-operated flashlight. Don’t use candles, matches or lighters during or after the earthquake. If there is a gas leak, an explosion could result. If you are in the kitchen, quickly turn off the stove and take cover at the first sign of shaking.
You are outdoors… a)Move into the open away from buildings, street lights and other utility wires. Save your head. b)Stay there till shaking stops. You are in vehicle…. a)Step down quickly or stay in the vehicle b)If you are driving move towards clear area like away from buildings, trees, flyovers, bridges and utility wires. c)Once shaking stops, proceed with caution. Avoid Bridges or ramps that might have been damaged.
After the earthquake,:- a)Help injured or trapped people b)Give first aid where appropriate. Do not move seriously injured persons unless they are in immediate danger of further injuries. c)Stay out of the damaged building. Return home only when the authorities say it is safe d)Use the telephones only for emergency call e)Check for gas leakage. Leave the area if you smell gas.
