Earthquake

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Welcome

To The

Presentation

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PresentationEngineering Geology & Geomorphology

CEN-223

Instructor

Anisuzzaman Khan

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Group Name

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Topic

Earthquake and

Bangladesh

Group Members

Md. Saddam Husain

ID# 12206023

Md. Hasan Shahariar

ID#12206013

Md. Shakkik Zunaed

ID#12206004

Arun Chandra Acharjee

ID#12206066

Md. Oliullah Sheik

ID#12206067

Md. Shariful Haque RobinID#12206049

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Contents

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Topic TopicWhat is Earthquake Major Earthquakes Zone in the World

The Focus and Epicenter of an Earthquake Tsunami

Types of Earthquake Earthquakes Zone in Bangladesh

Elastic Rebound Theory Last 2 Years Earthquake Statistic in Bangladesh & Places Near Bangladesh

Seismic Waves Earthquake and Dhaka City

Faults Earthquake Preventive Design

How does earthquake occurs Effect of Earthquake

The Seismograph Positive Effects of Earthquake

The Richter Scale Basic Recommendations for Earthquake Protection

What is Earthquake?

A natural vibration of the ground or the earth crust produced by forces is called earthquake or seismic forces.

An earthquake is what happens when two blocks of the earth suddenly slip past one another.

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The Focus and Epicenter of an Earthquake

•The point within Earth where faulting begins is the focus

•The point directly above the focus on the surface is the epicenter

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Types of Earthquake

An earthquake, simply defined as the shaking of the earth’s surface. On the basis of depth of focus, earthquakes are classified into three types. Following are the three types of earthquakes:

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Types Depth of focus (km)

Shallow Earthquake 60

Intermediate Earthquake

60-300

Deep Earthquake > 300

Elastic Rebound Theory

Rocks bend under stress while storing elastic energy. When the strain in the rocks exceeds their strength, breaking willoccur along the fault.Stored elastic energy is released as the earthquake. Rocks "snap back”, or rebound to their original condition.

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Seismic Waves

Two types:

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Body waves Surface waves

P Wave S Wave R Wave L Wave

Body Waves

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P Wave

S Wave

Surface Waves

Rayleigh Waves and Love Waves Travel just below or along the ground’s surface Slower than body waves; rolling and side-to-side

movement Especially damaging to buildings

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Faults

A fault is a fracture in the Earth's crust

3 main fault groups

Faults are classified depending on how they move.

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The Normal Fault Strike-Slip Fault

Thrust Fault

Types of Fault

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Normal Fault

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Thrust Fault

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Strike Slip Fault

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How does earthquake occurs?

Most earthquakes happen along the edge of the oceanic and continental plates. [Oceanic plates are under water, continental plates are above.] The earth's crust (the outer layer of the planet) is made up of a bunch of pieces, called plates. The plates get moved around by the liquid layers of magma underneath the Earth's crust. The plates are always bumping into each other, and pulling away from each other or past each other. Earthquakes usually happen when two plates are running into each other or sliding past each other. They can also happen along faults, too though.

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The Seismogram The device which records

Earth tremors

A pendulum swings when the earth moves

The pen attached to the pendulum records the movement

Pendulum

Pen

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The Richter Scale

Measures earthquake magnitude.

Based on the amplitude of the wave produced on the Seismograph.

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How are Earthquakes Measured? Richter Scale

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Major Earthquakes Zone in the World

• Red dots are shallow

• Green are intermediate depth

• Blue and purple are deep

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The 10 Most Powerful Recorded Earthquakes

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Location Date Magnitude1. Chile 22 May 1960 9.52. Prince William Sound, Alaska 28 March 1964 9.23. Off the west coast of northern Sumatra

26 December 2004

9.1

4. Kamchatka 4 November 1952

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5. Arica, Peru (now part of Chile) 13 August 1868 96. North Pacific coast of America 26 January 1700 9

(estimated)7. Off Bio-Bio, Chile 27 February

20108.8

8. Coast of Ecuador 13 January 1906 8.89. Lisbon 1 November

17558.7

10. Assam-Tibet 15 August 1950 8.6

Tsunami

A tsunami is a giant wave (or series of waves) created by an undersea earthquake, volcanic eruption.

Period 10 - 60 min, Wavelength 100 - 800 km, velocity 230 m/sec (500 mph)

At coast waves slow down and pile up and come on shore like a very rapidly rising tide

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Earthquakes in Bangladesh

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Earthquakes Zone in Bangladesh

In the north and northeast of Bangladesh, there are areas of high seismic activity and some of the major earthquakes originating in these areas. The whole of Bangladesh is divided into three seismic zones. The northern part of the country that includes the greater districts of Rangpur, Mymensingh, and Sylhet are in the Zone-I where earthquake shock of maximum intensity.

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The Zone-II includes the greater districts of Dinajpur, Bogra, Dhaka and Chittagong and the shocks of intensity of VIII are possible. The southern part of the country, the least active region, where the maximum intensity is not likely to exceed VII, is in the Zone-III. The experts suggest not to construct normal buildings with more than 60m height.

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Earthquakes Zone in Bangladesh cont.

Last 2 Years Earthquake Statistic in Bangladesh & Places Near

Bangladesh1. 1 years ago, Sylhet,

Bangladesh, 60 km depth.2. 1 years ago, Dhaka,

Bangladesh 45 km depth3. 1 years ago, Sikkim,

India, 57 km depth4. 2 years ago, Assam, India

53 km depth.5. 2 years ago,

Rangamati,Bangladesh, 48 km depth

6. 2 years ago, Manipur, India, 69 km depth.

7. 2 years ago, Maulvi Bazar, Sylhet, Bangladesh, 73 km depth 31

Earthquake and Dhaka City

Geologically active faults within 50 to 500 km distance from Dhaka.

Dhaka is among the 20 major world cities that are at the greatest risk from earthquakes.

Some of these earthquakes especially the 1762, 1812, 1865,1885 and 1897 happened in Dhaka.

If 7-8 grade in Richter Scale earthquake happen in Dhaka 70-80 percent of the concrete structures in the city would just collapse & 30,00,000 peoples will die.

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Effect of Earthquake

Ground shaking: Shaking of the ground caused by the passage of seismic waves, especially surface waves near the epicenter of the earthquake are responsible for the most damage during an earthquake.

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Effect of Earthquake Cont.

Damage to man-made structures: Damage to man-made structures, such as roads, bridges, dams and buildings from ground motion.

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Fires: Fires, often associated with broken electrical and gas lines, is one of the common side effects of earthquakes. Gas is set free as gas lines are broken and a spark will start bringing "inferno". To complicate things water lines are broken and so there is no water to extinguish the fire.

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Flooding: Flooding can come from many sources such as broken water main pipes, dams that fail due to the earthquake and earthquake-generated tsunamis.

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Tsunami:

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Positive Effects of Earthquake

Give knowledge insight in Geology Push Minerals and Metals to the Surface Make Fossil Fuels Easier to Access

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Earthquake Preventive Design

All structure should be designed according to BNBC – 2006 code

33% extra reinforcement provision to reduce earthquake effect

Residential building (5/ 6 storied) may be constructed with L-type corner column and 2/3 T-type inner column tied with beam

To make it tight 8”x 12” column section with 5” to 8” brick wall thickness may be selected

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Earthquake Preventive Design Cont.

Furthermore, the following general principles may be followed:

(a) Ht. of each floor should be 10’

(b) Foundation must be laid on hard soil

(c) Framed structure should be preferred rather than brick structure

(d) Where frame structure is not possible, brick wall should be reinforced vertically & horizontally

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Basic Recommendations for Earthquake Protection

Have ready first-aid kit, torches, battery-operated radio, batteries etc and some provisions in a place known to everyone.

Make an emergency action plan and ensure that the family gathers in a secure place.

Prepare a telephone list so that, if necessary, you can call the civil protection, fire, medical emergency or police services.

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Before the Earthquake:


If you are inside a building, stay inside; if you're outside, remain outside.

Inside a building, look for strong structures, underneath a table or bed, underneath a door lintel, next to a pillar, supporting wall or in a corner and protect your head.

Do not use the lift and never run headlong towards the exit.

Extinguish all fires. Do not use any type of flame (match, lighter, candle, etc.) during or immediately after the tremor 43

During the earthquake:


keep calm and ensure that others do the same. Prevent any panic situations.

Check whether anyone is hurt; give them any necessary first aid.

Do not repair damage immediately, except if there is broken glass or bottles containing toxic or inflammable substances.

Keep away from damaged buildings. Move to open areas.

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After the Earthquake:

Any Enquiry?

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Earthquake

Environment

Transcript of Earthquake