Earthquakes <ul><li>Earthquakes are shaking or vibration of the earth's crust. They make the land move and the effects of earthquake vary upon the magnitude and intensity. Earthquakes occur every now and then all round the world, except in some place places which earthquakes occur rarely. The devastation of cities and towns is one of the effects of earthquake. Landslides and Avalanches are caused by movement of earthquakes. Huge rocks come tumbling down the mountains sometimes blocking the path of rivers. This can cause floods. Houses are broken down by earthquakes. A huge Tidal wave called Tsunami which is derived from a Japanese word Tsu meaning harbor and Nami meaning wave. These tidal waves from the sea towards the land causing huge floods. </li></ul>
The Ten Largest Earthquakes Since 1900 Location Date Magnitude 1. Chile May 22, 1960 9.5 2. Prince William Sound, Alaska March 28, 1964 9.2 3. Andreanof Islands, Aleutian Islands March 9, 1957 9.1 4. Kamchatka Nov. 4, 1952 9.0 5. Off western coast of Sumatra, Indonesia Dec. 26, 2004 9.0 6. Off the coast of Ecuador Jan. 31, 1906 8.8 7. Rat Islands, Aleutian Islands Feb. 4, 1965 8.7 8. Northern Sumatra, Indonesia March 28, 2005 8.7 9. India-China border Aug. 15, 1950 8.6 10. Kamchatka Feb. 3, 1923 8.5
1906 San Francisco The San Francisco earthquake of 1906 was a major earthquake that struck San Francisco, CA and the coast of Northern California at 5:12 A.M. on Wednesday, April 18, 1906. The most widely accepted estimate for the magnitude of the earthquake is a moment magnitude. At the time, 376 deaths were reported; the figure was fabricated by government officials who felt that reporting the true death toll would hurt real estate prices and efforts to rebuild the city
Predicting Earthquakes <ul><li>Because of their devastating potential, there is great interest in predicting the location and time of large earthquakes. Although a great deal is known about where earthquakes are likely, there is currently no reliable way to predict the days or months when an event will occur in any specific location. </li></ul>In the past there have been many earthquakes that led to massive loss of life and property, and they all struck with little or no warning. Japan has probably the most advanced earthquake detection system in the world, yet was caught completely unawares by the Kobe Earthquake of 1995.
Earthquakes proof structure <ul><li>An earthquake-proof building is a building that has been built to survive an earthquake. The building is built with special technology that has materials made in earthquake areas. No building, however, can be made 100% safe and building earthquake proof structures to be more effective is just trial and error. </li></ul>
Primary and secondary waves <ul><li>Secondary waves are transverse waves, </li></ul><ul><li>which make the earth shake from side to side. </li></ul><ul><li>Slower than Primary waves, they average about </li></ul><ul><li>4 km/s so arrive second. </li></ul>Primary waves are longitudinal waves that push and pull the earth. They are the fastest body wave, averaging speeds of about 6 km/s, so arrive first.