Earthquakes

Information

An earthquake is a phenomenon that occurs without warning and involves violent shaking of the ground and everything over it. It results from the release of accumulated stress of the moving lithospheric or crustal plates. The earth's crust is divided into seven major plates, that are about 50 miles thick, which move slowly and continuously over the earth's interior and several minor plates. Earthquakes are tectonic in origin; that is the moving plates are responsible for the occurrence of violent shakes. The occurrence of an earthquake in a populated area may cause numerous casualties and injuries as well as extensive damage to property.

The Earthquake Risk in India

India's increasing population and extensive unscientific constructions mushrooming all over, including multistoried luxury apartments, huge factory buildings, gigantic malls, supermarkets as well as warehouses and masonry buildings keep - India at high risk. During the last 15 years, the country has experienced 10 major earthquakes that have resulted in over 20,000 deaths. As per the current seismic zone map of the country (IS 1893: 2002), over 59 per cent of India’s land area is under threat of moderate to severe seismic hazard-; that means it is prone to shaking of MSK Intensity VII and above (BMTPC, 2006). In fact, the entire Himalayan belt is considered prone to great earthquakes of magnitude exceeding 8.0-; and in a relatively short span of about 50 years, four such earthquakes have occurred: 1897 Shillong (M8.7); 1905 Kangra (M8.0); 1934 Bihar-Nepal (M8.3); and 1950 Assam-Tibet (M8.6). Scientific publications have warned of the likelihood of the occurrence of very severe earthquakes in the Himalayan region, which could adversely affect the lives of several million people in India.

At one time regions of the country away from the Himalayas and other inter-plate boundaries were considered to be relatively safe from damaging earthquakes. However, in the recent past, even these areas have experienced devastating earthquakes, albeit of lower magnitude than the Himalayan earthquakes. The Koyna earthquake in 1967 led to revision of the seismic zoning map, resulting in deletion of the non-seismic zone from the map. The areas surrounding Koyna were also re-designated to Seismic Zone IV, indicating high hazard. The occurrence of the Killari earthquake in 1993 resulted in further revision of the seismic zoning map in which the low hazard zone or Seismic Zone I was merged with Seismic Zone II, and some parts of Deccan and Peninsular India were brought under Seismic Zone III consisting of areas designated as moderate hazard zone areas. Recent research suggests that as understanding of the seismic hazard of these regions increases, more areas assigned as low hazard may be re-designated to higher level of seismic hazard, or vice-versa.

The North-Eastern part of the country continues to experience moderate to large earthquakes at frequent intervals including the two great earthquakes mentioned above. Since 1950, the region has experienced several moderate earthquakes. On an average, the region experiences an earthquake with a magnitude greater than 6.0 every year. The Andaman and Nicobar Islands are also situated on an inter-plate boundary and frequently experience damaging earthquakes.

The increase in earthquake risk is due to a spurt in developmental activities driven by urbanization, economic development and the globalization of India’s economy. The increase in use of high-technology equipment and tools in manufacturing and service industries has also made them susceptible to disruption due to relatively moderate ground shaking. As a result, loss of human life is not the only determinant of earthquake risk any more. Severe economic losses leading to the collapse of the local or regional economy after an earthquake may have long-term adverse consequences for the entire country. This effect would be further magnified if an earthquake affects a mega-city, such as Delhi or Mumbai.

Zone Map

Do's and Dont's

What to Do Before an Earthquake

• Repair deep plaster cracks in ceilings and foundations. Get expert advice if there are signs of structural defects.
• Anchor overhead lighting fixtures to the ceiling.
• Follow BIS codes relevant to your area for building standards
• Fasten shelves securely to walls.
• Place large or heavy objects on lower shelves.
• Store breakable items such as bottled foods, glass, and china in low, closed cabinets with latches.
• Hang heavy items such as pictures and mirrors away from beds, settees, and anywhere that people sit.
• Brace overhead light and fan fixtures.
• Repair defective electrical wiring and leaky gas connections. These are potential fire risks.
• Secure water heaters, LPG cylinders etc., by strapping them to the walls or bolting to the floor.
• Store weed killers, pesticides, and flammable products securely in closed cabinets with latches and on bottom shelves.
• Identify safe places indoors and outdoors.
• Under strong dining table, bed
• Against an inside wall
• Away from where glass could shatter around windows, mirrors, pictures, or where heavy bookcases or other heavy furniture could fall over In the open, away from buildings, trees, telephone and electrical lines, flyovers and bridges
• Know emergency telephone numbers (such as those of doctors, hospitals, the police, etc)
• Educate yourself and family members

Have a disaster emergency kit ready

• Battery operated torch with extra batteries
• Battery operated radio
• First aid kit and manual
• Emergency food (dry items) and water (packed and sealed)
• Candles and matches in a waterproof container
• Knife
• Chlorine tablets or powdered water purifiers
• Can opener.
• Essential medicines
• Cash and credit cards
• Thick ropes and cords
• Sturdy shoes

Develop an emergency communication plan

• In case family members are separated from one another during an earthquake (a real possibility during the day when adults are at work and children are at school), develop a plan for reuniting after the disaster.
• Ask an out-of-state relative or friend to serve as the 'family contact' after the disaster; it is often easier to call long distance. Make sure everyone in the family knows the name, address, and phone number of the contact person.

Help your community get ready

• Publish a special section in your local newspaper with emergency information on earthquakes. Localize the information by printing the phone numbers of local emergency services offices and hospitals.
• Conduct week-long series on locating hazards in the home.
• Work with local emergency services and officials to prepare special reports for people with mobility impairment on what to do during an earthquake.
• Provide tips on conducting earthquake drills in the home.
• Interview representatives of the gas, electric, and water companies about shutting off utilities.
• Work together in your community to apply your knowledge to building codes, retrofitting programmes, hazard hunts, and neighborhood and family emergency plans.

What to Do During an Earthquake

Stay as safe as possible during an earthquake. Be aware that some earthquakes are actually foreshocks and a larger earthquake might occur. Minimize your movements to a few steps that reach a nearby safe place and stay indoors until the shaking has stopped and you are sure exiting is safe.

If indoors

• DROP to the ground; take COVER by getting under a sturdy table or other piece of furniture; and HOLD ON until the shaking stops. If there is no a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building.
• Protect yourself by staying under the lintel of an inner door, in the corner of a room, under a table or even under a bed.
• Stay away from glass, windows, outside doors and walls, and anything that could fall, (such as lighting fixtures or furniture).
• Stay in bed if you are there when the earthquake strikes. Hold on and protect your head with a pillow, unless you are under a heavy light fixture that could fall. In that case, move to the nearest safe place.
• Use a doorway for shelter only if it is in close proximity to you and if you know it is a strongly supported, load bearing doorway.
• Stay inside until the shaking stops and it is safe to go outside. Research has shown that most injuries occur when people inside buildings attempt to move to a different location inside the building or try to leave.
• Be aware that the electricity may go out or the sprinkler systems or fire alarms may turn on.

If outdoors

• Do not move from where you are. However, move away from buildings, trees, streetlights, and utility wires.
• If you are in open space, stay there until the shaking stops. The greatest danger exists directly outside buildings; at exits; and alongside exterior walls. Most earthquake-related casualties result from collapsing walls, flying glass, and falling objects.

If in a moving vehicle

• Stop as quickly as safety permits and stay in the vehicle. Avoid stopping near or under buildings, trees, overpasses, and utility wires.
• Proceed cautiously once the earthquake has stopped. Avoid roads, bridges, or ramps that might have been damaged by the earthquake.

If trapped under debris

• Do not light a match.
• Do not move about or kick up dust.
• Cover your mouth with a handkerchief or clothing.
• Tap on a pipe or wall so rescuers can locate you. Use a whistle if one is available. Shout only as a last resort. Shouting can cause you to inhale dangerous amounts of dust.
• Hello

Recover and Build

What to Do After an Earthquake

• Keep calm, switch on the radio/TV and obey any instructions you hear on it.
• Keep away from beaches and low banks of rivers. Huge waves may sweep in.
• Be prepared to expect aftershocks.
• Turn off the water, gas and electricity.
• Do not smoke and do not light matches or use a cigarette lighter. Do not turn on switches. There may be gas leaks or short-circuits. Use a torch.
• If there is a fire, try to put it out. If you cannot, call the fire brigade.
• If people are seriously injured, do not move them unless they are in danger.
• Immediately clean up any inflammable products that may have spilled (alcohol, paint, etc).
• If you know that people have been buried, tell the rescue teams. Do not rush and do not worsen the situation of injured persons or your own situation.
• Avoid places where there are loose electric wires and do not touch any metal object in contact with them.
• Do not drink water from open containers without having examined it and filtered it through a sieve, a filter or an ordinary clean cloth.
• If your home is badly damaged, you will have to leave it. Collect water containers, food, and ordinary and special medicines (for persons with heart complaints, diabetes, etc.)
• Do not re-enter badly damaged buildings and do not go near damaged structures.

Source: National Disaster Management Authority(NDMA),Government of India