Earthquake

Disaster Assessment

EARTHQUAKE

By: Dalpat Prajapati

Earthquake

What is EARTHQUAKE?

• Earthquake refers to the result of a sudden release of energy in the Earth's crust that creates seismic waves. It may also refer to sudden and violent shaking of the ground, sometimes causing great destruction.

What CAUSES Earthquakes?

• An earthquake is caused by a sudden slipon a fault. Stresses in the earth's outer layer push the sides of the fault together. Stress builds up and the rocks slips suddenly, releasing energy in waves that travel through the earth's crust and cause the shaking that we feel during an earthquake. An EQ occurswhen plates grind and scrape against each other.

Types Of FAULT

Strike-slip Thrust Normal

The form of faulting depends upon the type of plate motion and nature of rocks.

STRIKE SLIP Fault

Strike-slip faults are vertical (or nearly vertical) fractures where the blockshave mostly moved horizontally. If the block opposite an observer lookingacross the fault moves to the right, the slip style is termed right lateral; if the block moves to the left, the motion is termed left lateral.

THRUST Fault

A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lowerstratigraphic position are pushed up and overhigher strata. They are often recognized because they place older rocks above younger. Thrust faults are the result of compressional forces.

NORMAL Fault

A fault in which the hanging wall has moved downward relative to the footwall.

Earthquake Terms

Where do earthquakes occur? Is it random? Is any place safe or free of earthquakes?

SHALLOW-FOCUSDEEP-FOCUS earthquakes

EARTHQUAKES & VOLCANIC ACTIVITY

AFTERSHOCKS

EARTHQUAKE SWARMS

Earthquake swarms are sequences of earthquakes striking in a specific area within a short period of time. They are different from earthquakes followed by a series of aftershocks by the fact that no single earthquake in the sequence is obviously the main shock, therefore none have notable higher magnitudes than the other.

When an earthquake occurs, the energy is

dissipated into the surrounding medium

through seismic waves.

SEISMIC WAVES

Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.

Type of Seismic waves

• There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are Body waves and Surface waves. • Body waves can travel through the earth's inner layers, but surface waves can only move along the surface of the planet like ripples on water. Earthquakes radiate seismic energy as both body and surface waves.

BODY WAVES

P-waves; also known as primary waves or pressure waves

S-waves; also referred to as secondary or shear waves

P- waves

S- waves

SURFACE WAVES

• Love and Raleigh waves

Love waves

Raleigh waves

HOW IS EARTHQUAKE INTENSITY MEASURED?

There are currently two “measuring” schemes used to

“quantify” or “qualify” the destructiveness or power of an

earthquake.

1) The Mercalli Intensity scale (it is qualitatively based)

2) The Richter Magnitude scale (it is quantitatively

based)

HOW COMMON ARE EARTHQUAKES?Magnitude (Richter Scale) Number per Year

0 – 3.4 >800,000

4.9 – 5.4 1400

5.5 – 6.1 500

7.0 – 7.3 15

>8 1 every 10 years

INDUCED SEISMICITY

EFFECTS OF EARTHQUAKE

Shaking and Ground Rupture

• Shaking and ground rupture are the main effects createdby earthquakes, principally resulting in more or less severe damage to buildings and other rigid structures. • The severity of the local effects depends on the complex combination of the earthquake magnitude, the distancefrom the epicenter, and the local geological and geomorphological conditions, which may amplify or reduce wave propagation. The ground-shaking is measured by ground acceleration.

Landslides and Avalanches

• Earthquakes, along with severe storms, volcanic activity, coastal wave attack, and wildfires, can produce slope instability leading to landslides, a major geological hazard. Landslide danger may persist while emergency personnel are attempting rescue.

Fires

• Earthquakes can cause fires by damaging electrical power or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started.For example, more deaths in the 1906 San Francisco earthquake were caused by fire than by the earthquakeitself.

Soil Liquefaction

• Soil liquefaction occurs when, because of the shaking, water-saturated granular material (such as sand) temporarily loses its strength and transforms from a solid to a liquid. Soil liquefaction may cause rigid structures, like buildings and bridges, to tilt or sinkinto the liquefied deposits.

Tsunami

• Large waves produced by an earthquake or a submarine landslide can overrun nearby coastal areas in a matter of minutes. • Tsunamis can also travel thousands of kilometers across open ocean and wreak destruction on far shores hours after the earthquake that generated them.• Ordinarily, subduction earthquakes under magnitude 7.5 on the Richter scale do not cause tsunamis, although some instances of this have been recorded. Most destructive tsunamis are caused by earthquakes of magnitude 7.5 or more.

Flood

• Earthquakes may cause landslips to dam rivers, which collapse and cause floods. • The terrain below the Sarez Lake in Tajikistan is in danger of catastrophic flood if the landslide dam formed by the earthquake, known as the Usoi Dam, were to fail during a future earthquake. Impact projections suggest the flood could affect roughly 5 million people.

Human Impacts

• An earthquake may cause injury and loss of life, road and bridge damage, general property damage (which may or may not be covered by earthquake insurance), and collapse or destabilization (potentially leading to future collapse) of buildings. The aftermathmay bring disease, lack of basic necessities, and higherinsurance premiums.

PREDICTION

• Many methods have been developed for predicting the time and place in which earthquakes will occur. Despite considerable research efforts by seismologists, scientifically reproducible predictions cannot yet be made to a specific day or month. However, for well-understood faults the probability that a segment may rupture during the next few decades can be estimated.• Earthquake warning systems have been developed that canprovide regional notification of an earthquake in progress, but before the ground surface has begun to move, potentiallyallowing people within the system's range to seek shelter before the earthquake's impact is felt.

Prediction

PREVENTION

Preparing for an Earthquake

1. Become familiar with earthquake terms.AftershocksEpicenterFaultFocusIntensityMagnitudeMercalli ScaleTidal waveTsunami

2. Safeguard your home by:• Bolting bookshelves, water heaters and cabinets to wall studs.• Anchoring things so that they will not move or fall during an earthquake is the most important thing you can do to make yourself safe. Keeping things in place also means they will not break.

Preparing for an Earthquake

During Earthquake

1. Get under a heavy table or desk and hold on, or sit or stand against an inside wall.

2. Keep away from windows.3. If indoors, stay indoors.4. If outdoors, stay outdoors away from falling

debris, trees and power lines.5. If in a car, stay in the car.6. Many injuries occur when people act on their

impulse to run.7. Train yourself to take cover where you are.

Responses Inside Buildings during an Earthquake

1. Drop, cover, and hold on.2. Get under a table.3. If there are no tables, get under or down between rows of

chairs or against inner walls.4. Do not stand in a doorway. Buildings today have so much

partitioning, much of which is temporary, that many doorways are actually weak points. Doorways are not a good solution in a group situation either.

5. If you have nothing to get under, sit down against an interiorwall or next to a chair, holding on if possible.

6. If you are in bed, it's best to stay there, hold on, and pullthe pillows over your head for protection.

7. If children are in another room, take cover in the closest safe place and call to them to do the same.

Responses If You Are Outside during an Earthquake

1. Outside, get away from buildings, walls, trees and power lines.1. If you cannot get clear of hazards, getting back inside

a building is better than staying on the sidewalk.2. Sidewalks next to buildings are among the worst places

to be.2. In a car, ease off the accelerator and slow down carefully. Do not stop on or under overpasses and bridges if you can avoid them. Be aware of what traffic around you is doing and act accordingly.3. If you live in coastal areas, be aware of possible tsunamis.

After Earthquake

1. Take basic precautions immediately after an earthquake. In addition to those outlined in the General Family Preparedness, Residential Fires and Hazardous MaterialsAccidents sections you should:

2. Expect aftershocks.3. Avoid using vehicles except in emergencies.4. Check yourself for injuries and protect yourself by putting

on shoes, work gloves and any other protective gear at hand.5. If the electricity is off, turn on a flashlight.

After Earthquake6. Once you are sure that you're all right, check the people around you for injuries.

1. You might ask loudly, "Is everyone okay?" This will also help calm people.

2. The types of injuries that happen most often in an earthquake include cuts, bruises, fractures and physiological shock.

7. Check the entire building for structural damage and chemical spills. Refer to the section on Hazardous Materials Accidents for further response information.8. Check chimneys for cracks and damage. The initial check should be made from a distance. Have a professional inspect the chimney for internal damage that could lead to fire.

CASE STUDY

26th January, 2001Bhuj, Gujarat.Scale between 7.6 and 7.7

The 2001 Gujarat earthquake occurred on January 26, 2001, India's 52nd Republic Day, at 08:46 AM local time (3:16 UTC) and lasted for over two minutes. The epicentre was about 9 km south-southwest of the village of Chobari in Bhachau Taluka of Kutch District of Gujarat, India. The earthquake reached a magnitude of between 7.6 and 7.7 on the moment magnitude Scale and had a maximum felt intensity of X (Intense) ontheMercalli intensity scale. The quake killed around 20,000 people (including 18 in South eastern Pakistan), injured another 167,000 and destroyed nearly 400,000 homes.

10 BIGGESTEARTHQUAKE

22 May, 1960Valdivia, Chile.R. Scale 9.51655 People Deaths

1

28 March, 1964Prince William Sound, AlaskaR. Scale 9.2 1400 People Deaths

2

26 December, 2004Sumatra, IndonesiaR. Scale 9.1227,900 People Deaths

3

11 March, 2011Sendai, JapanR. Scale 9.015,883 People Deaths

4

04 November , 1952Kamchatka, RussiaR. Scale 9.0

5

627 February, 2010Bio-bio, ChileR. Scale 8.8800,000 People Deaths

31 January, 1906The coast of EcuadorR. Scale 8.81505 People Deaths

7

02 April, 1965Rat Islands, Alaska R. Scale 8.7

8

28 March 2005Sumatra, IndonesiaR. Scale 8.61313 People Deaths

9

15 August 1950Assam - TibetR. Scale 8.6780 People Deaths

10

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Earthquake

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