ppt on Earthquakes

earthquake is defined as a sudden movement of earth’s crust or upper mantle

1. PPT ON EARTHQUAKES NAME :SRINIVAS REDDY BRANCH : CIVIL ENGINEERING

2. EARTHQUAKE An earthquake is defined as a sudden movement of earth’s crust or upper mantle . I t caused by the movement along a fault plane or by volcanic activity and resulting in generation of seismic waves which can be destructive.

3. The most common scale used for measuring an earthquake is Richter Scale. It should be understood that Richter scale is a logarithmic scale. What this means is an earthquake measuring 6.0 is 10 times more powerful than an earthquake measuring 5.0 WHAT DO WE USE TO MEASURE EARTHQUAKES ?

4. CLASSIFYING AN EARTHQUAKE The impact of an earthquake (at any location) is characterized by two primary characteristics : 1.Intensity : describes the level of shaking during an earthquake . Higher the value higher is the magnitude 2.Epicenter : It denotes the exact location , where the earthquake is originated.

5. EARTHQUAKE HAZARDS /DISASTERS The most common kinds of loss that are caused by an earthquake (depending on the severity) are : Damage to structures Effect of ground shaking Ground displacement F ire Sea activity Landslides

6. CAUSES OF EARTHQUAKES Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little. They don't just slide smoothly; the rocks catch on each other. The rocks are still pushing against each other, but not moving. After a while, the rocks break because of all the pressure that's built up. When the rocks break, the earthquake occurs. During the earthquake and afterward, the plates or blocks of rock start moving, and they continue to move until they get stuck again. The spot underground where the rock breaks is called the  focus  of the earthquake. The place right above the focus (on top of the ground) is called the  epicentre  of the earthquake.  

7. DISTRIBUTION OF EARTHQUAKES : The Earth's crust is broken up into pieces called plates. Heat rising and falling inside the mantle creates  convection currents  generated by radioactive decay in the core. The convection currents move the plates. Where convection currents diverge near the Earth's crust, plates move apart. Where convection currents converge, plates move towards each other. The movement of the plates, and the activity inside the Earth, is called  plate tectonics . Plate tectonics cause earthquakes and volcanoes. The point where two plates meet is called a  plate boundary . Earthquakes and volcanoes are most likely to occur either on or near plate boundaries.

8. HAZARDOUS EFFECTS OF EARTHQUAKES Collapsing buildings, walls, bridges, falling furniture or objects, shattering glass windows and mirrors.  Falling electricity lines Rock slides and/or landslides on mountains and hillsides Floods caused by the collapse of dam walls Tsunamis Liquefaction

9. EARTH QUAKE HAZARDS IN INDIA

10. 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. In fact, the entire Himalayan belt is considered prone to great earthquakes of magnitude exceeding 8.0 . EARTH QUAKE HAZARDS IN INDIA

11. Latest version  of seismic zoning map of India given in the  earthquake resistant design code of India [IS 1893 (Part 1) 2002] assigns  the earthquake zoning map of India divides India into 4seismic zones (Zone 2, 3, 4 and 5 ) Zones according to is 1893 (part 1) 2002: Zone 5: It covers the areas with the highest risks zone that suffers earthquakes of intensity MSK IX or greater. The region of Kashmir, the western and central Himalayas, North and Middle Bihar, the North-East Indian region and the Rann of Kutch ,the Andaman and Nicobar group islands fall in this zone .

12. Zone 4 This zone is called the High Damage Risk Zone and covers areas liable to MSK VIII. The IS code assigns zone factor of 0.24 for Zone 4. The Indo- Gangetic basin, Delhi,  Jammu and Kashmir ,In Maharashtra, the Patan area ,In Bihar the northern part of the state like- Raksaul , Near the border of India and Nepal, is also in zone no-4. Zone 3 The Andaman and Nicobar Islands , parts of Kashmir , Western Himalayas fall under this zone. This zone is classified as Moderate Damage Risk Zone which is liable to MSK VII. and also 7.8 Zone 2 This region is liable to MSK VI or less and is classified as the Low Damage Risk Zone

13. Perception of Earthquake Earthquake is such a disaster, which cannot be predicted. Thus, the only way to reduce the damages and losses due to an earthquake is effective preparedness . However, in most of the countries, an earthquake occurs once in several years, which may vary from 10 to 50 or even 100 years. Thus, obviously the priority of earthquake is lower than other more frequent disasters like floods, cyclones and draughts . Consequently, in most of the countries, earthquake disaster remains within a dilemma of sudden occurrence versus infrequent occurrences

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