What causes earthquake?

by Aisha Ajekigbe

Have you ever imagined buildings moving, being displaced from where it is situated and found 20 to 30 feet beneath the ground? Your imagination isn’t far-fetched; it sure happens when an Earthquake occurs.

An earthquake, also known as quake, tremor or temblor is the percentile shaking of the surface of the earth resulting from the sudden release of energy in the earth’s crust to create seismic waves. Earthquake is a natural phenomenon which is a non-artificial event, that is, an event not produced by humans. It is one of the natural geological phenomenon which science has not been able to predict accurately.

We only hear about it once in a while even though it occurs all the time, all over the earth. This is because the vast majority of these quakes are very weak and not even noticed. Major earthquakes are very much less frequent but are mostly destructive. Major earthquakes usually do not occur alone; there is usually one at another nearby location known as foreshocks, which are smaller earthquakes that happens in the same place before the major one takes place.

It is known that earthquake are caused by disturbances deep down inside the uppermost layer of the earth. The outermost layer of the earth is not in a single piece but is broken into number of plates known as lithospheric plates or tectonic plates. It may surprise you, but these plates are moving around very slowly just a few millimetres every year due to the movement of the molten magma inside the earth. The movements of these plates cause changes on the surface of the earth and can cause an earthquake.

When the plates try to slide past each othe, the boundaries of the plates get interlocked due to friction, but the rest of the plates keep moving. This cause a tension to build up in the plates. When the force of moving plates overcomes the friction of the edges, all the stored energy gets released, the earth shakes at this point. The energy gives rise to shock or seismic waves very much like ripples in a pond, when a stone is thrown into it. These shock waves shake the earth as they move outward through it. When the waves reach the surface of the earth, they shake the ground and anything on it.

Geologists usually express the intensity of an earthquake in terms of a magnitude on a scale known as the Richter Scale. The Richter scale, named after Dr. Charles F. Richter, is the scale used for measuring the strength of an earthquake, in terms of the amplitude of its seismic waves.
This scale is not a simple scale. On the scale, an increase of two in the magnitude means 100 times more destructive energy.

The earthquake strikes suddenly, violently without warning at any time of the day or night. If an earthquake occurs in a populated area, it can cause death and injuries and property loss. It is therefore important that we identify the potential hazards beforehand and take necessary precautions to protect ourselves as best as we can. People living in seismic zones where the earthquake are most likely to occur have to be specially prepared.

  1.  All the building in seismic zones need be designed so that they can withstand major tremors. It is advisable to make the structure simple so that it is ‘Quake Safe’.
  2. Since some building may catch fire, it is necessary that all the building have their fire fighting equipment in order.
  3. Safer places indoors, as well as outdoors, must be clearly identified.
  4. An emergency communication plan should be made available.
  5. Disaster management supplies (like flashlights, first aid box etc.) should be available on hand.