Earth-quakes

1. The intensity and magnitude measure the strength of the earthquake. These are obtained by detecting the seismic waves using instruments called seismograph or seismometer.
2. Intensity is a measure of how hard the earthquake shakes the ground. It is determined through the effects produced by the earthquake. Intensity varies from one place to another.
3. While the intensity of a specific earthquake varies, its magnitude does not vary.

1. Faulting of the lithosphere caused by tectonic movement where one plate slides over another plate.
2. Volcanism can cause occurrence of the earthquake. This is because the magma moves under the influence of intense pressure from within the earth's interior.
3. Mass wasting like landslide and rock fall can cause occurrence of earthquake, but this is for local scale.
4. Falling objects from the atmosphere such as meteorites may lead to the shaking earth's crust.
5. Man's influence through his activities such as mining using explosives like dynamites and transport vessels like trains and heavy trucks.

Seismic waves can be categorized as follows:

1. Body Waves. Are waves which travel through the crust and are of two types:
   • Primary Waves, which cause the crustal rock to move back and forth in the direction of wave movement.
   • Secondary Waves. Are waves, which cause the crustal rock to move side to side i.e. right angles to the direction of wave movement.
2. Surface Waves. These travel through the surface and are of two types:
   • Love Waves. Which cause the surface rock to move side to side of right angles to the direction of wave movement.
   • Rayleigh Waves. Wave, which cause the surface, waves to have a circular movement very similar to that of water wave movement.

1. They can cause loss of life and property.
2. They can displace parts of the earth's crust vertically or laterally.
3. They can raise or lower parts of the sea floor.
4. They can raise or lower coastal rocks.
5. They can cause landslide and open up deep cracks in the surface rocks.

1. Refraining from building high-rising structures on the land vulnerable to earthquake as well as strengthening buildings by using reinforced concrete, steel frames, deep foundations and light roofs.
2. Geologists should detect epicenters and tell the people to evacuate the places likely to be affected by earthquakes.
3. To avoid constructing very large water bodies like Kariba dam which can cause the earthquakes due to the weight of water and other materials.
4. Discouraging the use of explosives like dynamites in breaking the rocks during mining and construction operations.