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domingo, 28 de noviembre de 2010

Earthquakes - Terremotos

Earthquakes are among the deadliest natural disaster, causing the largest number of casualties, the highest death tolls, and the greatest destruction. In 1556 in China, the deadliest earthquake in history killed 830,000 people. But many other other have caused the death of more than 100,000 people, and it is not unusual, even in modern times, for an earthquake death tolls to reach 20,000 to 30,000 people with hundreds of thousands left homeless.
There are four factor that affect the casualty rate and economic impact of earthquakes: MAGNITUDE, LOCATION, QUALITY OF CONSTRUCTION OF BUILDINGS, AND TIMING.

MAGNITUDE, or strength of an earthquake, is usually measured in the Richter scale (although nowadays Mw scale is more used, i will write about it...), ranging from 1 to 10, with 10 being the greatest. Earthquakes over 6 on the Richter scale (shallow, less than 70 km depth) are often deadly, and those over 8 are generally catastrophic, causing terrible damage.

LOCATION, however, a severe earthquake is located far from population centers does not cause the same damages as a less severe one that occurs in the middle of a city. As an example in 1960, the strongest earthquake ever recorded, 9.5 on the Richter scale, struck in the Pacific Ocean near the Chilean coastline, killing over 2,000 people and injuring other 3,000. If this quake had struck a city, it would have been catastrophic, and hundred of thousands might have been killed. Similarly in Alaska, in 1964, a magnitude 9.2 earthquake hit an area with few people and the dead toll was 117.

QUALITY OF CONSTRUCTION OF BUILDINGS, furthermore, modern building construction techniques can lessen the death toll and economic impact of a moderate earthquake that would otherwise cause severe destruction of older-style buildings. In 2003, a terrible earthquake in the historic city of Ban in Iran caused the destruction of over 90% of the buildings, mostly due to old construction.

TIMING. the time of occurrence of an earthquake can affect the number of deaths and casualties. Earthquakes that occur in the night, when people are indoors, usually cause greater death toll than ones that occur when people are outdoors.

Natural Disaster: a disaster caused by nature not people.
Death Toll: the number of poeple killed
Casualties/Victims: people who are either injured or killed in a disaster
Missing: people who can't be found after the disaster
Homeless: people who have no place to live after a disaster (extracted from: Sawslow&ascher)

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