Earthquakes GL3

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  • Created by: Kay
  • Created on: 28-04-11 15:12

Earthquakes - WJEC / GL3 revision

1. Prediction.

There are many ways in which scientists claim to predict earthquakes. Some of them are reasonably understandable, others are outright ridiculous.

  • Animal behaviour - This is one of the most ridiculous claims by the general public. Many people report their pets acting oddly just before an earthquake occurs - enough it seems that WJEC now accept it as a valid answer in your GL3 exam paper.
  • Radon - Emission of radon as a quake precursor was studied in the 1970s and 80s with no reliable results and continued to be dismissed by most seismologists until recently.
  • Foreshocks - These are common in high risk areas. In some cases, they can be call for an evacuation but many lead to nothing.

Unfortunately, scientists have still not worked out a way to tell us the main components needed to save lives. We need to know WHEN, WHERE and HOW BIG.


Haicheng, China 1975.

After a series of foreshocks, some of which damaged buildings, local government leaders evacuated much of the populace before the devastating magnitude 7.3 quake hit. This saved thousands of lives just by a rough guess.

However, the following year the government failed to do the same for the Tangshan M7.8 'quake, which killed thousands.


The Mercalli scale measures the amount of damage caused by an earthquake (roughly). It corrolates to the Richter scale in some ways

Richter =

1.0 - 3.0 = I (Mercalli)

3.1 - 3.9 = II - III

4.0 - 4.9 = IV - V

5.0 - 5.9 = VI - VII

6.0 - 6.9 = VII…


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