Earthquakes or tremors are an intense shaking-up of the Earth's surface, caused by movements in the outermost layer -- a common natural phenomenon.
The Earth's solid crust and the stiff layer of the mantle – known as lithosphere – are made up of giant puzzle pieces called tectonic plates. These plates are constantly shifting as they drift around on the viscous, or slowly flowing, mantle layer below.
The location where an earthquake begins is called the epicentre. An earthquake's most intense shaking is often felt near the epicentre. However, the vibrations from an earthquake can be felt and detected hundreds or even thousands of miles away from the epicentre.
Aftershocks occur near the fault zone where the mainshock rupture has occurred and are part of the "readjustment process” after the main slip on the fault. Aftershocks become less frequent with time, although they can continue for days, weeks, months, or even years for a very large mainshock.
Earthquakes don't kill, buildings do.
Experts say 90% of the deaths from an earthquake happen when people are trapped inside a building constructed through a flouting of rules and if they do not know what to do during or after a quake.
Earthquakes affect faulty buildings and other structures. Buildings and roads develop cracks or tilt or collapse when struck by a strong tremor. Thus, damage from earthquakes can be reduced by identifying the faulty buildings and retrofitting them, and making new structures earthquake-resistant.
Bangladesh sits on three fault zones, and three cities – Sylhet, Chittagong and Dhaka – are in the hot zones. Experts say a strong earthquake stemming from any of the three faults will cause massive destruction to buildings, bridges and supply channels of utility services, and may cause the death of hundreds of thousands of people.
What to do?
BEFORE
* Identifying potential hazards ahead of time can save lives.
* Repair plaster cracks in ceilings and foundations.
* Place large or heavy objects on lower shelves.
* Repair defective electrical wiring and leaky gas connections.
* Identify interior columns and beams, which can serve as safe zones.
* Hang emergency telephone numbers in a suitable place in your house.
DURING
* Some earthquakes are actually foreshocks and a larger earthquake might occur immediately.
* Stay away from glass, windows and anything that could fall.
* Do not use the elevators.
* If outdoors, move away from buildings, street lights and utility wires.
* If in a moving vehicle, stop and stay in the vehicle, avoid being under trees, overpasses and utility wires.
* If trapped under debris, do not light a match or move about or kick up dust.
* Tap on a pipe or wall so rescuers can locate you.
* Cover your mouth with a handkerchief or clothing.
AFTER
* Check yourself for injuries, help injured or trapped persons.
* Don't try to move seriously injured people unless they are in immediate danger of further injury.
* Clean up spilled medicines, bleaches, gasoline or other flammable liquids immediately.
* Inspect your home/office for damage. If it is damaged or a crack develops, go outside.