1. Earthquake hazard -
true or false answers

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1. The largest earthquake during the last week was magnitude 8.2 on the Richter Scale.
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3. 2. All earthquakes are located on or near the plate margins.

4. 3. The majority of severe earthquakes occur at destructive plate boundaries.
81% of the world’s biggest earthquakes have occurred around the ‘ring of fire’

5. 4. There is more than one type of seismic wave released from an earthquake
There are 4!

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5. The South East Asian earthquake on Boxing Day 2004 was the largest ever recorded.
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7. 6. Scientists have made assumptions about the structure
of the earth as a result of measuring seismic waves.
True - S waves only travel through more ‘solid’ material and therefore can’t pass through the liquid outer core

8. 7. Earthquakes occur in the UK as a result of our proximity to the Mid Atlantic Ridge.
between 150 and 200 earthquakes are detected and located in the UK and surrounding waters, by the British Geological Survey annually. Although distant from the nearest plate boundary, the Mid-Atlantic Ridge, earthquakes occur as crustal stresses within the tectonic plates are relieved by movement occurring on pre-existing fault planes.

9. 8. The Richter scale and Mercalli scale measure earthquakes in different ways.
The Richter Scale is calculated from the amplitude of the earthquake where as the Mercalli scale measures the impacts of the earthquake

10. 9. There is no way of predicting when earthquakes will occur.
In 1975 in Haicheng, China an evacuation warning was issued the day before a M 7.3 earthquake.
In the preceding months changes in land elevation and in ground water levels, widespread reports of peculiar animal behaviour, and many foreshocks had led to a lower-level warning. An increase in foreshock activity triggered the evacuation warning.
Unfortunately, most earthquakes do not have such obvious precursors.