Seismic waves

Seismology is the study of earthquakes and seismic waves that move through and around the earth. A seismologist is a scientist who studies earthquakes and seismic waves.

Seismic waves

P waves, also called compressional or longitudinal wavesgive the transmitting medium—whether liquid, solid, or gas—a back-and-forth motion in the direction of the path of propagation, thus stretching or compressing the medium as the wave passes any one point in a manner similar to that of sound waves in air.

In the Earth, P waves travel at speeds from about 6 km 3. As the waves enter the core, the velocity drops to about 8 km 5 miles per second. It increases to about 11 km 6. The speed increase with depth results from increased hydrostatic pressure as well as from changes in rock composition; in general, the increase causes P waves to travel in curved paths that are concave upward.

S waves, also called shear or transverse wavescause points of solid media to move back and forth perpendicular to the direction of propagation; as the wave passes, the medium is sheared first in one direction and then in another.

In the Earth the speed of S waves increases from about 3. Like P waves, S waves travel in curved paths that are concave upward.

Seismic waves

Of the two surface seismic waves, Love waves —named after the British seismologist A. Lovewho first predicted their existence—travel faster.

They are propagated when the solid medium near the surface has varying vertical elastic properties. Displacement of the medium by the wave is entirely perpendicular to the direction of propagation and has no vertical or longitudinal components.

The energy of Love waves, like that of other surface waves, spreads from the source in two directions rather than in three, and so these waves produce a strong record at seismic stations even when originating from distant earthquakes.

The other principal surface waves are called Rayleigh waves after the British physicist Lord Rayleighwho first mathematically demonstrated their existence. Rayleigh waves travel along the free surface of an elastic solid such as the Earth. Their motion is a combination of longitudinal compression and dilation that results in an elliptical motion of points on the surface.

Of all seismic waves, Rayleigh waves spread out most in time, producing a long wave duration on seismographs.The latest earthquakes on a map with news, lists, and links.

Mapa de últimos terremotos incluso boletines, noticias y enlaces. Seismic wave definition, a wave of energy that is generated by an earthquake or other earth vibration and that travels within the earth or along its surface.

See more. A longitudinal wave is a wave in which the particles of the medium are displaced in a direction parallel to the direction of energy transport. A longitudinal wave can be created in a slinky if the slinky is stretched out horizontally and the end coil is vibrated back-and-forth in a horizontal direction.

Earthquakes radiate seismic energy as both body and surface waves. Body Waves. Traveling through the interior of the earth, body waves arrive before the surface waves emitted by an earthquake. These waves are of a higher frequency than surface waves. P Waves. The first kind of body wave is the P wave or primary wave.

This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a . This work is licensed under a Creative Commons Attribution-NonCommercial License. This means you're free to copy and share these . Significant Earthquakes Archive. The USGS Earthquake Hazards Program is part of the National Earthquake Hazards Reduction Program (NEHRP), established by Congress in We monitor and report earthquakes, assess earthquake impacts and hazards, and research the causes and effects of earthquakes.

Seismic Evidence for Internal Earth Structure