Definition of Seismic Waves
Seismic waves are waves of energy that travel through the Earth's layers, and are a result of an earthquake, volcanic eruption, magma movement, large landslide, or large man-made explosions that give out low-frequency acoustic energy. These waves carry the energy released during these events from their source, called the hypocenter, outwards in all directions.
Types of Seismic Waves
There are two main types of seismic waves: Body Waves and Surface Waves. Body waves travel through the Earth's interior and include P-waves (Primary or compressional waves, which are the fastest and travel through solids, liquids, and gases) and S-waves (Secondary or shear waves, which are slower and can only travel through solids). Surface waves, such as Love waves and Rayleigh waves, travel along the Earth's surface and are responsible for most of the damage caused by earthquakes, as they have larger amplitudes and longer durations.
Detection and Measurement
Seismic waves are detected and recorded by instruments called seismographs. These devices measure ground motion and produce a seismogram, a graph showing the arrival times and amplitudes of different waves. The data from a network of seismographs allows scientists to pinpoint the epicenter and depth of an earthquake, as well as calculate its magnitude.
Importance in Studying Earth's Interior
The study of seismic waves is crucial for understanding the Earth's internal structure. By analyzing how P-waves and S-waves travel, reflect, and refract at different depths, seismologists can infer the composition, density, and physical state (solid or liquid) of the Earth's layers, including the crust, mantle, and core. For example, the discovery that S-waves cannot pass through the outer core provided key evidence that it is liquid.