Earthquakes and seismic waves — Earth science, 11–13 years
Understand how sudden movement along a fault releases stored energy, and how seismic waves reveal where an earthquake began.
A sudden release of energy
An earthquake happens when rocks suddenly move along a fracture called a fault. For a while, friction can hold the rocks still while forces build up. When the rocks slip, stored energy travels through the ground as seismic waves, making the surface shake.
Why study seismic waves?
An earthquake begins underground, where nobody can watch it directly. Scientists needed a way to locate its starting point and compare its size. Seismometers record wave arrivals; differences in arrival times from several stations allow the focus to be located, while wave strength helps describe the event.
Locating an earthquake
Imagine three stations detect the same earthquake. At station A, the fast P wave arrives 20 seconds before the slower S wave; at B the gap is 40 seconds, and at C it is 60 seconds. A larger gap means the station is farther away, so the source lies where circles around A, B and C meet.
Magnitude is not shaking
It is reasonable to think that the earthquake that shakes you most is the biggest one. Shaking at a place also depends on distance, ground type, building design and depth. Magnitude describes the energy released at the source; intensity describes the effects at a particular location.
Reducing earthquake risk
Earthquake science helps engineers design buildings that bend without collapsing, fasten shelves and plan safer bridges. Monitoring can give warnings when the first, faster waves arrive before stronger waves, though it cannot predict the exact day of an earthquake. Preparedness matters because people can act before or during the shaking.
Keep exploring
Other languages
Loading MyLeoNes™…