Earthquake

• ➢ The network of seismographic (seismograph is the instrument used to measure earthquakes) stations all over the world record dozens of earthquakes every day. Most of them are not felt by human beings as they are minor quakes only.
• ➢ The occurrence of a severe earthquake is limited to a few regions in the world.
• ➢ The point within the earth’s crust where an earthquake originates is called as the focus or hypocenter or seismic focus. It generally lies within a depth of 6 kms in the earth crust.
• ➢ The point vertically above the focus on the earth’s surface is called as the epicenter.
• ➢ The intensity of earthquake will be highest in the epicenter and decreases as one moves away.
• ➢ All-natural earthquakes take place in the lithosphere (i.e., the region which constitutes the earth’s crust and rigid upper part of the mantle).

Earthquake waves or Seismic waves The earthquake which originates in the lithosphere propagates different seismic waves or earthquake waves. Earthquake waves are basically of two types – body waves and surface waves.

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