| Earthquakes around the world |
| Aftershocks usually follow an earthquake. The first earthquake is mostly the strongest. Many weaker earthquakes or aftershocks occur after the main quake for next 2 to 3 days. But aftershocks due the main earthquake take place for weeks and months, less in frequency and strength. Even after 2 years aftershocks have been recorded. The readjustment of the plates is never perfect after a quake. Their touching edges need to be smoother. This additional realignment creates the smaller aftershocks. When the earth�s plates finally stop grinding against each other, the surface landscape changes over huge areas near the earthquake�s cente. The already weakened structures may be damaged further by aftershocks. The number or timing of aftershocks can not be predicted. Past records show that each year more than 1,000 eartquakes of manitude 5 and more take place. More than 10,000 quakes of varying magnitudes between 4 to 5 take place every year. The number grows larger for weaker quakes. The number of earthquakes with magnitudes of 8 and greater is less than one each year. However, each year there are about 10 earthquakes of magnitude 7 or greater and 100 earthquakes of magnitude 6 or greater. So far no scientific group could relate their occurance with other natural events, like tides, full moon, solar cycle, position of stars or other heavenly bodies. However staistical data are analysed to find any relationship with all other known events to find a possible hint to earthquake's occurance either before or after any regular or odd activity of nature. Any weak hint to the trigger mechanism may lead to the answer one day. The intensity of eartquakes are related to the damage due to shaking in the following table. Intensity 1 and 2. Only a few people may feel a very slight shaking. No damage is caused. Intensity 3 and 4. Observers do not notice anything if they are outdoors. People inside a static stucture or building notice swinging lamps, waves in liquids, slight rattling of a window. Intensity 5 and 6. Almost everyone feels movement. Doors swing. Dishes are broken. Pictures on the wall move. Liquids might spill out of open containers. Objects fall from shelves. Pictures fall off walls. Furniture moves. Trees and bushes shake. Damage is slight in poorly built buildings and structures. |
| Intensity 7 and 8. Drivers feel trouble in steering their cars as they shake. Some furniture breaks. Loose bricks fall from buildings. Damage is slight to moderate in well-built buildings; considerable in poorly built buildings. Tall structures such as towers and chimneys might twist and fall. Tree branches break. Hillsides might crack. Water levels in wells might change. Animals and birds get scared. Several aftershocks are expected for days. Intensity 9 and 10. IX. Well-built buildings suffer severe damage. Houses move off their foundations. Water pipes are broken. Reservoirs suffer serious damage. Some bridges are destroyed. Dams are seriously damaged. Large landslides occur. The ground cracks in large areas. Railroad tracks are bent slightly. People can not stand or run. Intensity 11 and 12. All buildings and bridges collapse. Large cracks appear in the ground. Underground pipelines are destroyed. Railroad tracks are badly bent. Almost everything is destroyed. Objects are thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move. |
| Millions of people may never experience an earthquake although they are very common events on this planet. Today, somewhere, an earthquake will occur. It may be so light that only sensitive instruments will detect its details, it may shake buildings, rattle windows, and throw small objects, or it may be quite strong to damage property, cause death and misery. |
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| An apartment building in San Francisco�s Marina District shows heavy damage from a 1989 earthquake |
| recent earthquake |
| cause of earthquake |
| earthquake picture |
| earthquake information |
| earthquake occurrence |
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