Fault
Also called: Faulting · Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Class 9, Ch 2 "Shaping of the Earth's Surface"; Class 11, Ch 3 "Interior of the Earth"; Class 11, Ch 5 "Geomorphic Processes"
Meaning
A fault is a sharp break in the rocks of the crust. The blocks on each side try to move in opposite directions. The weight of the rocks above and friction lock them together, so stress builds up. When the stress beats the friction, the blocks bend and then slip suddenly, releasing energy as an earthquake. This sudden snap is called elastic rebound. Faults can move in different ways. In a thrust fault one block is pushed up over another. In a strike-slip fault the blocks slide past each other sideways.
Example
The Gorkha earthquake of 25 April 2015 (Mw 7.8) in central Nepal was caused by thrust movement on the Main Himalayan Thrust. The Myanmar earthquake of 28 March 2025 (Mw 7.7) struck on the Sagaing Fault near Mandalay, which is a strike-slip fault.
Don't confuse with
- Fold: here rocks bend into upfolds and downfolds without breaking. A fault is a break along which blocks move.