How Do We Gauge An Earth Quake And The Intensity Of Its Damage?

The intensity or rating of an earth quake is measured using a scale called the "Mercalli Intensity Scale".  Ratings of an earth quake and its effects on humans, living creatures and man made structures are decided on a scale of 1 to 12 with 1 being the weakest and 12 being the strongest. The following are the considerations on the scale:


1. Earth movement is not felt by people.
  
2. Earth movement is felt by people resting or people on the top floors of high rise buildings

3. People inside their houses feel the movement and hanging objects swing. People outside don't feel anything.

4. People indoors feel the movement, objects swing, doors and windows rattle, a few people feel the movement outside, parked cars rock.

5. Almost everyone feels the movement, people sleeping wake up, doors and windows open or close, trees swing, liquids spill out of their containers, pictures move, dishes and small objects topple over or break.

6. Everybody can feel the movement, pictures fall off, Plaster cracks, and people have trouble walking, furniture moves, objects fall from shelves, trees and shrubs shakes light damage observed in poorly built buildings.

7. People find it difficult to stand, people feel their cars shaking, furniture may break, there is slight to moderate damage in buildings, loose bricks fall off the buildings. Poorly built structures sustain considerable damage.

8. Drivers find it difficult to control their vehicles, level of water in wells changes, trees and branches break, hillsides with wet ground cracks, foundations of homes might shake or shift, towers and chimneys break off, damage to well built structures, poorly built structures collapse.

9. Reservoirs suffer severe damage, foundations of homes move, the ground cracks, under ground pipes break, well built buildings suffer considerable damage.

10. Most buildings and their foundations get destroyed, bridges and dams are destroyed, landslide occurs, water is thrown on banks and canals, railroad tracks get bent and there are huge cracks on the ground.

11. Most buildings collapse, bridges break, large cracks appear in the ground, railroad tracks are destroyed, underground pipes are destroyed.

12. Almost everything is destroyed, the earth heaves in ripples and waves, large rocks move and objects get flung around.