Why does the ground suddenly shake? It is a question many students may be asking after recent earthquake tremors were felt across parts of northern India. Google Trends has also shown a sharp rise in searches related to the recent earthquake. But the science behind an earthquake is much bigger than one event: it begins with the slow movement of enormous pieces of Earth’s outer shell.
On October 6, 2026, an earthquake in Uttarakhand was felt in Delhi-NCR. India’s Department of Science and Technology explains that seismic activity in the region is linked to strain built up by the northward movement of the Indian Plate and its collision with the Eurasian Plate.
So, what actually causes an earthquake?
The simplest answer is: rocks suddenly slip along a fault after stress has built up underground.
Earth’s outer shell is divided into huge pieces called tectonic plates. These plates move extremely slowly, but they do not always slide smoothly. Friction can lock sections together while the plates continue pushing, pulling or sliding. Stress builds until the rocks can no longer hold it. A sudden slip releases stored energy as seismic waves, which travel through the Earth and produce the shaking we feel.
What is a fault?
A fault is a fracture or zone of weakness in Earth’s crust where blocks of rock can move relative to one another. When movement happens suddenly along a fault, an earthquake can occur.
Think of two rough blocks being pushed against each other. They may stay stuck for a while even though the force continues. When the force becomes greater than the friction holding them together, they suddenly move. An earthquake is the underground version of that release of stored energy.
Why does the ground shake?
The sudden movement at a fault releases energy in the form of seismic waves. These waves spread outward from the earthquake’s source. When they reach the surface, they make the ground—and buildings, roads and everything on it—move.
What are the epicentre and hypocentre?
- Hypocentre: The point below Earth’s surface where the earthquake begins.
- Epicentre: The point on Earth’s surface directly above the hypocentre.
These two terms help scientists describe where an earthquake starts and where its location projects onto the surface.
Why does India get earthquakes?
India sits on the Indian Plate, which is moving northward and interacting with the Eurasian Plate. The collision has helped create and continue deforming the Himalayan region, where stress can accumulate and be released through faults and other weak zones.
That does not mean every earthquake in India happens in exactly the same way. Earthquakes can also occur within plates, away from their main boundaries, when older weaknesses in the crust are reactivated by stresses transmitted through the plate.
Can scientists predict an earthquake?
Not in the precise sense of saying exactly when, where and how large the next earthquake will be. Scientists can identify regions with earthquake hazards and study faults, past earthquakes and the stresses affecting Earth’s crust. But the USGS says scientists currently cannot predict earthquakes with that level of certainty.
Is a bigger earthquake always coming after a smaller one?
No. A smaller earthquake may later be identified as a foreshock if a larger earthquake follows it, but scientists can only know that after the larger event occurs. Earthquakes that follow a mainshock are called aftershocks.
How is an earthquake’s size measured?
Students often hear the phrase “Richter scale,” but modern earthquake science commonly uses moment magnitude to describe an earthquake’s size. Magnitude describes the size of the earthquake source, while intensity describes how strongly the ground shakes and what effects are observed at a particular location.
Three questions to remember
- Why do earthquakes happen? Stress builds in Earth’s crust and can be released suddenly when rocks slip along a fault.
- Why do they shake the ground? The sudden release sends seismic waves through the Earth.
- Can we predict the exact next earthquake? No—not with the precision of a date, location and magnitude.
The bigger lesson
Earthquakes can be frightening, but understanding them replaces some of the mystery with science. The ground beneath us may look solid and permanent, yet Earth’s outer shell is constantly changing on geological timescales.
That is the kind of question worth asking: If the ground looks still, how can an entire continent be moving? The answer takes us from a classroom geology lesson to the forces that have shaped mountains, oceans and the planet itself.
Sources: U.S. Geological Survey (USGS); Government of India’s Department of Science and Technology; Google Trends.
