Earthquakes bring many changes to the natural and cultural landscape, but the greatest damage caused when buildings fail to survive an earthquake. Earthquake does not directly kill people, but people are killed by their own constructed buildings, which are vulnerable to an earthquake. Avoiding constructing buildings while fearing earthquakes is irrational. So in order to protect ourselves from the hazards of earthquakes, we need to take two precautionary measures; one is to design buildings in such a way, that they could survive earthquakes, and the second is a general safety measure that people can take during an earthquake. Before discussing the safety measures that are necessary during an earthquake, we are going to discuss the design and construction of the buildings to protect them from damage.
Protection of buildings:
An earthquake vibrates the ground, and as a result, the buildings also start vibrating. The bottom of the buildings moves to-and-fro as per the vibrations of the ground. But due to an increase in length with the height of the building the upper part of the building sways back and forth and gets pushed and pulled with high displacement. The whole building does not move back and forth. The bottom of the building just vibrates slightly because of being fixed with the ground, and the top sways a lot in the back and the fourth direction. Which may result in the building crack or even collapse.
This movement sets up a lot of stress in the building, and when the stress becomes saturated, the building cracks and collapse. It is somewhat like holding a stick at one end firmly and pushing the other end too much, the stick will ultimately break. In case both ends of the stick are openly moved, the stick will never break.
There are two ways of protecting buildings; buildings should be stronger enough, which could resist an earthquake, and buildings should move accordingly to the vibration.
Strengthening the buildings:
There are many ways to achieve strength in the buildings. One way is to insert diagonal pieces in the walls and divide them into rectangular areas. This protects the walls from getting quashed when there is a sideways force exerted on them.
Let’s take the example of an empty matchbox, which can easily be quashed when there are no match sticks inside it. If we try to quash the match box filled with match sticks, it will require greater force to get quashed. This is how the diagonal pieces inside the walls and roof can protect them from squashing.
Allowing the buildings to move according to the earthquake t vibrations:
Because the buildings are fixed by their bottom in the ground, and the top of the buildings sways during seismic vibration, stress arises. Especially in earthquakes of high magnitude, the upper part of the buildings starts swaying more as compared to the bottom. The excessive swaying creates more stress in the skeleton of the building. So in order to prevent the buildings from stress, it is reasonable to allow the whole mass of the building to sway equally. In modern architecture, the buildings can be placed on the bearings, which allow the building to freely move back and forth. This is done by placing the strong bearings on the thick (fixed) prestressed concrete foundation. The buildings placed on the bearings can move both forth-and-back, and sideways as per vibration that is caused by the earthquakes. By this method, the bottom of the building also moves equally to the top of the building, thus reducing the swinging of the building. This method is modern and mechanically advanced, and the cost of this method is also higher if compared to the construction of the fixed buildings.
What safety measure can be taken in order to protect ourselves during an earthquake?
In case we are trapped in a building during an earthquake, the foremost preference should be to save, somehow, our lives. Life is the most precious thing in the world. We should follow the following measures in order to protect ourselves from the lethal consequences of the earthquakes.
1. Stay away from non-fixed item in the room, like windows, glass objects, mirrors and things that can fall like book cases and cabinets.
2. Crawl under a table or bed or crouch near an inner wall or doorway and protect your head and face with your arms.
3. In order to get support hold on some thing which is unlikely to fall.
4. Never use the lift.
5. Turn off the power supply.
6. In case, you are in outdoors, just stay away from the buildings, poles, bridges, and trees.
7. Generally after shocks follow an earthquake. You should be ready for the aftershocks.
8. People in earthquake-prone areas should be particular about fixing tall, heavy furniture to the wall and anchoring heavy appliances well. They should avoid placing breakable and heavy objects on high shelves.