short notes on causes and prevention of earthquakes..
Answers
We cannot prevent natural earthquakes from occurring but we can significantly mitigate their effects by identifying hazards, building safer structures, and providing education on earthquake safety. By preparing for natural earthquakes we can also reduce the risk from human induced earthquakes.
Earthquakes: Definition, Causes, Measures and Other Details
The sudden shaking or rolling of the earth’s surface is called an earthquake. Actually earthquakes occur daily around the world (according to one estimate, about 8000 occur every year), but most of them are too mild to be noticeable. We know of them only because they are recorded by instruments called seismographs (the Greek word seismos means ‘earthquake’).
How Earthquakes Occur:
Perhaps you remember that the earth is made up of three layers. At its heart is a core of iron, consisting of a solid sphere surrounded by a layer of hot, molten iron. Around the core is a mantle of soft, paste like rocks. And over the mantle rests the hard layer of rocks we call the crust. This crust is not a uniform, faultless shell. It is more like a jigsaw of blocks that fit together. The huge blocks that make up the crust are called tectonic plates.
The Plates of the crust float on the soft mantle
The heat inside the earth sets up a current in the mantle, keeping it in constant motion. This makes the plates of the crust move continually, like rafts on a gentle ocean. The movement sometimes causes the edges of the plates to grind against each other with a lot of force.
They may then get deformed, displaced, crushed or fractured. They may also slide under each other or move apart. Such changes in the plates send a tremor or set up vibrations through the crust, causing what we call an earthquake.
The edges of the tection plates may (a) slip under ever other, (b) move apart or (c) get displaced
Weak points:
Over millions of years, the movements of the tectonic plates have created mountains and valleys on the surface of the earth. They have also created certain weak points, called faults, in the crust. Most faults occur along the boundaries of the tectonic plates and these are the zones where earthquakes occur.