Page 11
EARTHQUAKES:
Earthquakes are vibrations of the earth caused by sudden movement of rocks that have been strained beyond their elastic limit.
Main causes of the earthquake are plate tectonics, volcanic eruption or anthropogenic activities like explosions, reservoir induced seismicity etc.
There is a release of huge amount of energy in the form of sound and seismic waves causing shaking of earth’s surface.
FOCUS: The point where earthquake generates
EPICENTRE: The point just above the focus on the surface
RICHTER SCALE: Measures the magnitude of earthquake
MERCALLI SCALE: Measures the intensity of an earthquake
The magnitude of the earthquake remains same everywhere while intensity decreases going away from the epicenter.
Depth of Focus:
The depth of an earthquake generally varies from about 10-700 km below the surface of the earth. Although the movement of material within the Earth occurs throughout the mantle and core, earthquakes are concentrated only in its 700 km. Within this range earthquakes can be grouped according to depth of focus.
Disasters & Disaster Management-IASbaba
Page 12
Shallow focus Earthquake: these earthquakes occur from the surface to the depth of 70km; they occur in all seismic belts and produce the largest percentage of earthquakes.
Intermediate focus Earthquake: 70 and 300km below the surface of the earth.
Deep focus Earthquake: 300 to 700km
Both the intermediate and deep focus earthquakes are limited in number and distribution.
The maximum energy released by an earthquake decreases with increase in depth. Hence most of the large and destructive earthquakes have shallow focus.
Consequences of Earthquakes:
Rise and subsidence of land surface- High magnitude earthquakes can create fissures and embankments and thus results into new landforms deforming the ground surface.
Enormous damage to property
Loss of human and animal life
Devastating fires, floods and landslides
Flash floods- Many a times due to earthquake the dams and embankments gets ruptured and causes flash floods resulting in loss of life and property.
Landslides
Tsunamis
The Indian subcontinent has a history of devastating earthquakes. The major reason for the high frequency and intensity of the earthquakes is that the Indian plate is driving into Asia at a
Disasters & Disaster Management-IASbaba
Page 13
rate of approximately 47 mm/year. Geographical statistics of India show that almost 54% of the land is vulnerable to earthquakes.
Center for Seismology, Ministry of Earth Sciences is nodal agency of Government of India dealing with various activities in the field of seismology and allied disciplines. The major activities currently being pursued by the Center for Seismology include—
Earthquake monitoring on 24X7 basis, including real time seismic monitoring for early warning of tsunamis
Operation and maintenance of national seismological network and local networks
Seismological data centre and information services,
Seismic hazard and risk related studies
Field studies for aftershock / swarm monitoring, site response studies
Earthquake processes and modeling
Disasters & Disaster Management-IASbaba
Page 14
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
Disasters & Disaster Management-IASbaba
Page 15
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);
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.
(NOTE: The following section might look irrelevant and too technical to you. But direct questions have been asked on the course of action during a hazard. These are the government guidelines given on the National Disaster Management Agency’s site. You are not supposed to memorize these points but read them once so that if a question is asked, you can be close to the government’s prescribed action and don’t end up writing some general random points.
This section will also help you in GS paper-4, where a case study can be asked, like, if you are a District Magistrate, what course of action will you take if a particular disaster strikes.)
Disasters & Disaster Management-IASbaba
Page 16
DOs and DON’Ts during Earthquake
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.
o Under strong dining table, bed
o Against an inside wall
o Away from where glass could shatter around windows, mirrors, pictures, or where heavy bookcases or other heavy furniture could fall over
o 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)
Disasters & Disaster Management-IASbaba
Page 17
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.
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.
Disasters & Disaster Management-IASbaba
Page 18
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.
Disasters & Disaster Management-IASbaba
Page 19
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.
Disasters & Disaster Management-IASbaba
Page 20
EARTHQUAKES:
Earthquakes are vibrations of the earth caused by sudden movement of rocks that have been strained beyond their elastic limit.
Main causes of the earthquake are plate tectonics, volcanic eruption or anthropogenic activities like explosions, reservoir induced seismicity etc.
There is a release of huge amount of energy in the form of sound and seismic waves causing shaking of earth’s surface.
FOCUS: The point where earthquake generates
EPICENTRE: The point just above the focus on the surface
RICHTER SCALE: Measures the magnitude of earthquake
MERCALLI SCALE: Measures the intensity of an earthquake
The magnitude of the earthquake remains same everywhere while intensity decreases going away from the epicenter.
Depth of Focus:
The depth of an earthquake generally varies from about 10-700 km below the surface of the earth. Although the movement of material within the Earth occurs throughout the mantle and core, earthquakes are concentrated only in its 700 km. Within this range earthquakes can be grouped according to depth of focus.
Disasters & Disaster Management-IASbaba
Page 12
Shallow focus Earthquake: these earthquakes occur from the surface to the depth of 70km; they occur in all seismic belts and produce the largest percentage of earthquakes.
Intermediate focus Earthquake: 70 and 300km below the surface of the earth.
Deep focus Earthquake: 300 to 700km
Both the intermediate and deep focus earthquakes are limited in number and distribution.
The maximum energy released by an earthquake decreases with increase in depth. Hence most of the large and destructive earthquakes have shallow focus.
Consequences of Earthquakes:
Rise and subsidence of land surface- High magnitude earthquakes can create fissures and embankments and thus results into new landforms deforming the ground surface.
Enormous damage to property
Loss of human and animal life
Devastating fires, floods and landslides
Flash floods- Many a times due to earthquake the dams and embankments gets ruptured and causes flash floods resulting in loss of life and property.
Landslides
Tsunamis
The Indian subcontinent has a history of devastating earthquakes. The major reason for the high frequency and intensity of the earthquakes is that the Indian plate is driving into Asia at a
Disasters & Disaster Management-IASbaba
Page 13
rate of approximately 47 mm/year. Geographical statistics of India show that almost 54% of the land is vulnerable to earthquakes.
Center for Seismology, Ministry of Earth Sciences is nodal agency of Government of India dealing with various activities in the field of seismology and allied disciplines. The major activities currently being pursued by the Center for Seismology include—
Earthquake monitoring on 24X7 basis, including real time seismic monitoring for early warning of tsunamis
Operation and maintenance of national seismological network and local networks
Seismological data centre and information services,
Seismic hazard and risk related studies
Field studies for aftershock / swarm monitoring, site response studies
Earthquake processes and modeling
Disasters & Disaster Management-IASbaba
Page 14
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
Disasters & Disaster Management-IASbaba
Page 15
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);
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.
(NOTE: The following section might look irrelevant and too technical to you. But direct questions have been asked on the course of action during a hazard. These are the government guidelines given on the National Disaster Management Agency’s site. You are not supposed to memorize these points but read them once so that if a question is asked, you can be close to the government’s prescribed action and don’t end up writing some general random points.
This section will also help you in GS paper-4, where a case study can be asked, like, if you are a District Magistrate, what course of action will you take if a particular disaster strikes.)
Disasters & Disaster Management-IASbaba
Page 16
DOs and DON’Ts during Earthquake
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.
o Under strong dining table, bed
o Against an inside wall
o Away from where glass could shatter around windows, mirrors, pictures, or where heavy bookcases or other heavy furniture could fall over
o 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)
Disasters & Disaster Management-IASbaba
Page 17
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.
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.
Disasters & Disaster Management-IASbaba
Page 18
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.
Disasters & Disaster Management-IASbaba
Page 19
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.
Disasters & Disaster Management-IASbaba
Page 20
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