How earthquakes release energy — Earth science, 14–17 years
Stress can build where rocks are locked along a fault. When they suddenly slip, energy travels through Earth as seismic waves.
A sudden slip
An earthquake happens when stored strain in rocks is released suddenly. Usually the rocks lie along a fault, a fracture where blocks can move. The rupture starts underground at the focus, and the point directly above it on the surface is the epicentre.
Why scientists measure waves
People first needed a way to compare earthquakes without relying only on how frightening they felt. Seismic waves carry measurable energy and travel at known speeds. Their arrival times and sizes help scientists locate the source, estimate strength and study Earth’s hidden interior.
Finding an epicentre
A station records a P-wave at 12:00:00 and an S-wave at 12:00:10. Suppose this ten-second gap corresponds to 80 km on the travel-time graph. Draw a circle with radius 80 km around that station. Repeat with two other stations; where the three circles meet is the earthquake’s epicentre.
Magnitude is not shaking
It is easy to say an earthquake had one fixed ‘size’ everywhere. That mixes up magnitude with intensity. Magnitude describes energy released at the source; intensity describes the shaking and damage at a particular place, which can change with distance, ground and buildings.
Reducing risk
Earthquake science guides building rules, bridge design and emergency planning. Flexible structures, secure furniture and clear escape routes can reduce harm, but no forecast can promise the exact time and place of the next earthquake. Monitoring also supports early-warning systems that may provide seconds of notice.
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