Earthquakes GL3

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.

CASE STUDY:

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.

MERCALLI SCALE:

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…