An earthquake occurs due to a sudden release of energy in the Earth's crust that creates seismic waves. There are three main types of seismic waves - P waves, S waves, and surface waves. Earthquakes are caused by movements of tectonic plates. The effects of earthquakes include shaking, ground rupture, tsunamis, landslides and damage to infrastructure. Earthquake preparedness and mitigation measures can help reduce risks and impacts, such as retrofitting buildings, developing emergency response plans, and educating the public. Dhaka, Bangladesh is at high risk of earthquakes due to its location in a seismically active zone, with over 13 million people vulnerable to damage and loss of life from a major qu

1. Welcome to Our Presentation on Earthquake

2. Earthquake An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. It is also known as a quake, tremor, or temblor. Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth.

3. Seismic Wave Earthquakes, and other sources, produce different types of seismic waves which travel through rock, and provide an effective way to image both sources and structures deep within the Earth. There are three basic types of seismic waves in solids: P-waves, and S-waves

4. Seismic Wave Pressure waves or Primary waves (P-waves), are longitudinal waves that travel at maximum velocity within solids and are therefore the first waves to appear on a seismogram. S-waves, also called shear or secondary waves, are transverse waves that travel more slowly than P-waves and thus appear later than P-waves on a seismogram.

5. Seismic Wave Figure 1: Propagation of Seismic Wave

6. Plate Tectonics, the Cause of Earthquakes The plates consist of an outer layer of the Earth, the lithosphere, which is cool enough to behave as a more or less rigid shell. Occasionally the hot Asthenosphereof the Earth finds a weak place in the lithosphere to rise buoyantly as a plume, or hotspot. The satellite image below shows the volcanic islands of the Galapagos hotspot.

7. Earthquake occurrence in different plate tectonic settings There are three main plate tectonic environments: extensional, transform, and compressional. Plate boundaries in different localities are subject to different inter-plate stresses, producing these three types of earthquakes. Each type has its own special hazards. Plate Tectonics, the Cause of Earthquakes

8. Plate Tectonics, the Cause of Earthquakes Figure: Three main plate tectonic environments

9. Prediction techniques There is no perfect method for forcasting earthquake. In the effort to predict Earthquakes people have tried to associate an impending earthquake with such varied phenomena as seismicity patterns, electromagnetic fields (seismo-electromagnetics), ground movement, weather conditions and unusual clouds, radon or hydrogen gas content of soil or ground water, water level in wells, animal behavior, and t he phases of the moon

10. Effects/impacts of earthquakes Shaking and ground rupture Landslides and avalanches Fires Soil liquefaction Tsunami Floods Tidal forces Human impacts

11. Effects of earthquake Figure 2: 1755 copper engraving depicting Lisbon in ruins and in flames after the 1755 Lisbon earthquake, which killed an estimated 60,000 people. A tsunami overwhelms the ships in the harbor.

12. An example: Haiti A massive earthquake struck Haiti just before 5 p.m. on Jan. 12, about 10 miles southwest of Port-au-Prince, the country's capital. The quake was the worst in the region in more than 200 years. Magnitude of the Earthquake was 7.0 230,000 confirmed deaths occured A study by the Inter-American Development Bank estimates that the cost could be between $7.2 billion to $13.2 billion.

13. An example: Haiti Figure 3: A Haitian boy receives treatment at a Minustahlogistics base.

14. An example: Haiti Figure 4: Damaged buildings in Port-au-Prince

15. An example: Haiti Figure 5: A Haitian boy receives treatment at a Minustahlogistics base.

16. An example: Haiti Figure 6: Urban Search and Rescue specialists work at the Hotel Montana.

17. Earthquake preparedness Earthquake preparedness refers to a variety of measures designed to help individuals, businesses, and local and state governments in earthquake prone areas to prepare for significant earthquakes. Preparedness measures are part of the emergency management cycle, and can be refined through the use of an earthquake scenario Earthquake preparedness measures can be divided into: Retrofitting and earthquake resistant designs of new buildings and lifeline structures (e.g. bridges, hospitals, power plants). Response doctrines for state and local government emergency services. Preparedness plans for individuals and businesses.

18. Figure 8: A graphic representation of the four phases in emergency management. Earthquake preparedness

19. Mitigation Mitigation efforts attempt to prevent hazards from developing into disasters altogether, or to reduce the effects of disasters when they occur. Preparedness In the preparedness phase, emergency managers develop plans of action for when the disaster strikes. Response The response phase includes the mobilization of the necessary emergency services and first responders in the disaster area. Recovery The aim of the recovery phase is to restore the affected area to its previous state. It differs from the response phase in its focus; recovery efforts are concerned with issues and decisions that must be made after immediate needs are addressed.

20. What to Do Before an Earthquake Check for hazards in the home Identify safe places indoors and outdoors Educate yourself and family members Have disaster supplies on hand Develop an emergency communication plan Help your community get ready

21. What to Do During an Earthquake 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 isn’t a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building. If outdoors Stay there. Move away from buildings, streetlights, and utility wires. 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. 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.

22. What to Do After an Earthquake Expect aftershocks. Listen to a battery-operated radio or television. Use the telephone only for emergency calls. Open cabinets cautiously. Stay away from damaged areas. Be aware of possible tsunamis if you live in coastal areas. Help injured or trapped persons. Clean up spilled medicines, bleaches, gasoline or other flammable liquids immediately. Inspect the entire length of chimneys for damage. Inspect utilities. Check for gas leaks. Look for electrical system damage. Check for sewage and water lines damage.

23. Where is our position?

24. Where is our position? In the previous map it is obvious that Bangladesh is belonging to one of the most vulnerable earthquake zone of the world.

25. Earthquake risk of Dhaka Figure 10: Earthquake Hazard Zoning Map of Dhaka Megacity

26. Earthquake risk of Dhaka Figure 11: Map of major earthquakes of South Asia.

27. Earthquake risk of Dhaka Bangladesh, by and large, is seismically active. Dhaka has not been experienced with any moderate to large earthquake in historical past, even then the earthquake of December 19, 2001 with magnitude of 4.5 and focal depth of 10 km located very close to Dhaka is certainly an indication of its earthquake source and vulnerability. In addition, micro-seismicity data also supports the existence of at least four earthquake source points in and around Dhaka. The earthquake disaster risk index has placed Dhaka among the 20 most vulnerable cities in the world. Dhaka with its population of around 13 million and enormous poorly constructed and dilapidated structures signifies extremely vulnerable conditions for massive loss of lives and property in the event of a moderately large earthquake.

28. What should we do? Earthquake cannot be prevented. But certainly it is high time to be much more concerned about the probable impending earthquake in order to minimise the loss of lives and property in national interest. On the basis of the above facts, we should develop earthquake monitoring network in Bangladesh immediately. It is of prime importance to set a national institute of earthquake research to develop high skilled manpower that can perform the task for earthquake risk assessment and management.

29. Thank you