Types of earthquakes
Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Class 11, Ch 3 "Interior of the Earth"
Meaning
NCERT groups earthquakes into five types by cause. Tectonic earthquakes are the most common. They happen when rocks slide along a fault plane (a sharp break in crustal rocks). Volcanic earthquakes are a special kind of tectonic quake found only near active volcanoes. Collapse earthquakes are minor tremors caused when the roofs of underground mines cave in. Explosion earthquakes come from chemical or nuclear blasts. Reservoir-induced earthquakes happen near large reservoirs (big lakes behind dams).
Example
The Koyna earthquake in Maharashtra (11 December 1967, magnitude about 6.3) is India's standard case of a reservoir-induced quake. Bhuj in Gujarat (26 January 2001, Mw 7.7) was a tectonic quake. The Pokhran nuclear tests in Rajasthan (1974, 1998) set off explosion tremors.
Don't confuse with
- Magnitude vs intensity: the five types sort quakes by cause. Magnitude (Richter or Mw) measures the energy released, and intensity (Mercalli, I-XII) measures the damage seen.