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Earthquakes

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					               Earthquakes
• What F is the place where rock gives way and
  causes an earthquake?
• What S are the waves of energy that are
  released after rocks give way?
• What E is the area on the earth’s surface over
  the place where rocks give way?
• What A comes after an earthquake (secondary
  effect) and is caused by the rock readjusting?
• What R is the scale we use to measure
  earthquakes?
            Earthquake Video-Answers
Earthquakes are so dangerous because they are very quick and unexpected.
   In this century, earthquakes have killed around two million people
   even though the earth shook violently for less than an hour.
Many earthquakes happen without people noticing. There are around 1
   million earthquakes a year but are too small to be felt by people.
   Only 1-20 a year are strong earthquakes.
Without people, earthquakes would hardly be noticed. As some major
   cities are in earthquakes zones, earthquakes cause more deaths than
   any other hazards. Around 600 million people live in earthquake
   zones. Risk from earthquakes is part of life for those that live
   there.
Seismographs detect earthquakes. The problems for seismologists are
   that earthquakes can not be predicted and they can not be forecast.
   They can only be detected when they are actually happening.
Earthquakes are caused by movements in the earth’s tectonic plates.
   95% of earthquakes occur on plate boundaries.
One of the largest earthquakes this century was in Alaska in 1964. The
   earth shook for 7 minutes along 500 miles of the fault line.
   Anchorage was the hardest hit. The earthquake released the energy of
   12,000 Hiroshima sized atomic bombs. 115 people died in the
   earthquake.
In south China in 1976 the earthquake was much weaker than the Alaskan
   one, but the focus was much nearer the surface. This causes more
   damage than a stronger, deeper earthquake. 255,000 people died.
                          Earthquake Video: Part Two

During an earthquake the contents inside a building are tossed about and people
can be crushed and killed. Outside is no safer as debris falls from buildings and
roads collapse.

The greatest danger from earthquakes is fire due to overturned cookers, broken
gas mains and severed power cables. Water mains also shatter, depriving
emergency services of water to fight the fires. Fires are the worst cause of
destruction.

In the 1995 Kobe earthquake (in Japan) over five and a half thousand people
died. Fires burnt unchecked for several days. The ultimate danger is that they
develop into a fire storm where winds over 100 miles per hour fan the fire to blow
torch intensity.

The great Tokyo earthquake had a fire storm that killed more people than the
actual earthquake itself. A group of 40,000 people were sheltering in a park when
a fire storm blew in leaving only 30 survivors.
Worse effects are Tsunamis, giant tidal waves that crash into the shore. In the
Alaska earthquake the Tsunami killed more people that the earthquake itself.

In Kobe (Japan) whole offices fell into the streets so Emergency Services could not
get through to where they were needed. During earthquakes, medical services can
also be affected as hospitals collapse.

Transport systems are in ruin after an earthquake, especially elevated roads. Even
roads designed to withstand earthquakes with deep foundations and reinforced
construction have been destroyed in ways that people did not understand.
Liquefaction causes structures and buildings to sink into the ground.

Good construction also costs money. Many earthquake zones are in developing
countries where there is not much money. It means that there building and
transport systems may suffer more damage buildings in North America or Europe.

As well as death and injury, people also are affected by shock after an earthquake.
After an earthquake people need to try and turn off their gas and electricity supply
and store water but many are too shocked to do anything.
In Armenia on the 7th December 1998 a 40 second earthquake flattened towns
and caused 25,000 deaths and left ½ a million people homeless. Many people
were too shocked to cope with the situation. People had to try and find anyone
trapped under the rubble, but with little resources there was little hope for some.

Few survive being buried for a long period because of dehydration or severe
injuries. A sad but inevitable task was to dig out the dead, but as it was cold and
food was scarce this was a difficult task for the survivors.

There is some hope for rescuers. In Mexico City a group of 7 new born babies
managed to survive in a collapsed hospital for a week.

Many people are scared after an earthquake and refuse to return to their homes.
Some may spend days or weeks in the open, with good reason as aftershocks can
occur. These can be as destructive as the first earthquake.

In Assisi, Italy an earthquake destroyed many people’s houses. In one village, the
whole population was made homeless and six people died. It also destroyed the
town’s historical buildings. When people started to restore parts of a church that
had been damaged, there was an aftershock came and the roof of the building
collapsed. Four people died. There was no warning. If there was just a 20
second warning, more people could have survived.
 From the card sorts, fill in 3 sequences of events that happen during and after an earthquake using the gaps in the table:


Things that happen during an   1. Buildings Shake        2. Building Collapse   3. Roads           4. Gas pipes are
    earthquake are:                                                                 collapse or        broken
                                                                                    cracks
                                                                                    occur
A consequence of this is       1. People get injured     2.                     3.                 4.
    that...                         or die from
                                    falling debris

A result of this is that...    1. People get trapped     2.                     3.                 4.
                                    under rubble

This causes...                                                                  3.                 4.


What happens next? What could you put in the next row? What could happen next as a consequence of the above
effects? Write your thoughts in the boxes below.




Something that could happen    1.                        2.                     3.                 4.
   as a result of the above
   is that...

				
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