What is an Earthquake
Earthquakes are vibrations in the earth's crust They occur along all plate boundaries but are more destructive usually at destructive plate boundaries
How are they measured
The magnitude or size of an earthquake can be measured by an instrument called a seisometer and are shown on a seismograph. The earthquakes are measured on the Richter scale from a value of 1 to 10. Each level of magnitude is 10 times more powerful than the previous. Therefore a level 7 is 100 time more powerful than a level 5.
Why do some earthquakes cause more damage than others?
Some earthquakes take place in rural areas where few people live and little is damaged
If they occur near large urban areas with many people, transport services, large buildings and services such as gas and electricity - there can be a great amount of deaths and damage
In Poor countries - LEDC's they have poorly built buildings, few emergency facilities, and the equipment to help rescue people - a good term to use is that they have a poor infrastructure.
In rich countries - MEDC's such as the USA they prepare for an earthquake with drills and have a great deal of trained emergency personnel and equipment to go to help the injured. They also try to build to withstand earthquake damage - ie The Transamerica building
The time of day can be important - If the earthquake hits when it is the rush hour or when there is a large number of people located in a certain area - this can cause a great loss of life
Obviously if they occur near to coasts then Tsunamis can cause a great deal of damage and deaths such as the 2004 Boxing Day Tsunami