In lots of parts
of the world earthquakes are common. Countries like Japan, Turkey,
Italy and the west coast of America have many earthquakes every year.
Earthquakes
are caused by two of the earth's plates rubbing together which makes the
earth rumble and move. The plates do not move smoothly beside each
other along the fault lines and sometimes they
get stuck. Pressure builds up till the plates suddenly break free
and move. This is an earthquake. Sometimes they are small tremors,
but sometimes they are large quakes. The place where an earthquake
starts is called its epicentre.
The strength of earthquakes
is measured using a machine called a seismograph. Earthquakes are given
a measurement which is a number using a set of measurements called the
Richter Scale. The Richter Scale uses numbers to describe how strong an
earthquake is. Each number is ten times as strong as the number before,
so an Earthquake measured at 5 (moderate) on the Richter Scale, is ten
times as powerful as an earthquake that measured 4. Most earthquakes
of less than around 3.5 on the Richter scale cannot be felt by people.
When an earthquake starts
it can cause lots of damage. In Alaska an earthquake that measured
8.5 (one of the biggest earthquakes ever recorded) had its epicentre about
129km east of the city of Anchorage but it caused lots of buildings to
be destroyed and hundreds of people lost their homes.
There are not many earthquakes
in Australia because there are no major fault lines in Australia.
Sometimes there are small earthquakes and in 1989 an earthquake in Newcastle,
north of Sydney, which measured 5.6 on the Richter scale caused the first
recorded deaths from earthquake in Australia.
Click HERE
to see our model of an Earthquake.
