Earthquakes

Why in News?

Recently the National Capital Region, Delhi and adjoining regions faces a shallow earthquake of 4.0 magnitude with a focal depth of five kilometres.

• An earthquake is a phenomenon that occurs without warning and involves violent shaking of the ground and everything over it.
• It results from the release of accumulated stress of the moving lithospheric or crustal plates.
• An earthquake is the sudden movement of Earth’s crust at a fault line.
• It is also called as quakes, tremors, or temblors.
• Epicenter - The location where an earthquake begins is called the epicenter. An earthquake’s most intense shaking is often felt near the epicenter.
• However, the vibrations from an earthquake can still be felt and detected hundreds, or even thousands of miles away from the epicenter.
• The energy from an earthquake travels through Earth in vibrations called seismic waves, measured by seismometer.
• Types of energy

• Types Of Earthquake - Along with the tectonic earthquakes, there are also 3 types of earthquakes.
  • Volcanic - Earthquakes that occur in conjunction with volcanic activity
  • Collapse - Smaller-scale earthquakes that result from the subterranean collapse of caverns or mines
  • Explosion - Earthquakes caused by underground explosions of nuclear or chemical devices.
• Depth
  • Shallow earthquakes - 0 to 70 km deep
  • Intermediate earthquakes - 70 to 300 km deep.
  • Deep earthquakes - 300 to 700 km deep.
• Scenario in Delhi - Delhi lies in the Aravalli-Delhi Fold Belt, a seismically-active geological belt extending from southern and eastern Rajasthan to Haryana and Delhi.
• Over the years, the tectonic activity in the region has slowed down considerably, leading to greater geological stability. But some faults still remain, which give rise to occasional mild earthquakes.
• Medvedev-Sponheuer-Karnik scale – It is a measure of intensity, rather than strength, or energy released, which is described by magnitude.
• Delhi is classified in Zone 4, the 2^nd highest classification of areas based on their susceptibility to shaking experienced during an earthquake.

References

1. The Hindu | What is a shallow earthquake?
2. News 18 | What Is an Earthquake?