2. What are earthquakes and where do they occur? Earthquakes are vibrations caused by earth movements at plate boundaries and at major fault lines (cracks in the earth’s surface). They can occur at all 4 major plate boundaries but the most severe earthquakes are normally found at CONSERVATIVE and DESTRUCTIVE boundaries. CONSERVATIVE DESTRUCTIVE
6. How can we measure earthquakes? The largest earthquake ever recorded was in Chile. It measured 8.9 on the Richter Scale. This measures the magnitude of a tremor (how powerful it is) using an instrument called a seismograph. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. Although the Richter Scale has no upper limit, the largest known shocks have had magnitudes in the 8.8 to 8.9 range. It is a logarithmic scale which means that a size ‘6’ on the Richter Scale is 10 times larger than a size ’5’ and 100 times larger than a size ‘4’. Richter Scale The Richter Scale 1 2 3 4 6 5 9 8 7 10
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9. Copy and complete the boxes below using what you know about earthquakes. Think about the situation where the most and least damage would be caused by an earthquake Distance from the epicentre Weak earthquake, Doesn’t cause much damage Powerful earthquake, causes a lot of damage The state of preparation for an earthquake (country) Population density Type of land the area is built on Time of the day Time of the year
18. How can we try to manage the effects of earthquakes?
19. This is the Sky Tower in Auckland, New Zealand. Sky Tower is the tallest tower in the Southern Hemisphere and the twelfth tallest in the World. Sky Tower is 328 metres tall (more than 1,076 feet); that's about 37 buses standing end on end! Sky Tower weighs 21 million kilos (20,000 tonnes) which is equivalent to 6,000 elephants. Problem – Auckland is in an earthquake zone. How could you make buildings such as the Sky Tower more ‘earthquake proof’? Sky’s the limit!
20. Sky Tower is constructed from a high strength, high performance concrete. The main structure of Sky Tower is a reinforced concrete shaft measuring 12 metres in diameter. It is supported by eight reinforced concrete 'legs' at the base, connected to the shaft by a concrete collar and designed to spread force load. Sky Tower's foundations go down more than 15 metres. The tower was tested to see if it would withstand earthquakes. Analysis shows that an earthquake measuring 7.0 on the Richter scale, located 40 kilometres from Sky Tower on the Kerepehi Fault, would leave Sky Tower essentially undamaged. In the extreme event of a magnitude 8.0 earthquake occurring within 20 kilometres of the tower, analysis shows that Sky Tower would remain standing. What they did…
21. 1. predict water levels can rise in wells and lakes because of cracks in the rock a tiltmeter can check any movement within the rocks Can earthquakes be predicted and controlled? foreshocks before the main quake can be detected by a seismometer animals can act strangely before the earthquake
22. 2. plan What should people pack in their emergency kit? make an emergency plan organize regular ‘earthquake practices’ for offices and schools advise people to plan for an earthquake (eg tell them to turn off the gas, find a ‘safe’ place in their homes, pack an emergency kit) enforce regulations to make some buildings earthquake proof Design a poster reminding people what to do in an earthquake. How can we limit earthquake damage?
