A seismic wave is an elastic wave generated by an impulse such as an earthquake. Scientists deduced the structure of earth s interior and how waves move through it by analyzing thousands of earthquakes recorded at earth s surface. Animations by larry braile show the different wave behavior in the. Seismic wave, vibration generated by an earthquake, explosion, or similar energetic source and propagated within the earth or along its surface. You will see the waves changing names as the hit different parts of the earth s interior. P wave, the difference between p and s waves and p wave. P waves primary waves and s waves secondary waves or shear waves are the seismic waves that occur when an earthquake happens.
P waves the first kind of body wave is the p wave or primary wave. Surface waves are the slowest of all seismic waves, traveling at 2. These waves waves travel in a transversal direction. Body waves move through the interior of the earth and are made up of p waves red concentric and s waves white concentric lines. P waves primary waves s waves secondary waves p waves and s waves. Surface waves can only travel on the surface of the earth. The rayleigh surface waves are the waves that cause the most damage during an earthquake.
This is the fastest kind of seismic wave, and, consequently, the first to arrive at a seismic station. Swave seismic imaging of nearsurface sediments using. The swave is a transverse wave, meaning that, in the simplest situation. In an earthquake, body waves produce sharp jolts, while rolling motions of surface waves do most of the damage in an earthquake. In the animations shown here, the p and s waves are shown propagating.
The location where earthquakes originate is called the focus. In seismology, swaves, secondary waves, or shear waves sometimes called an elastic swave are a type of elastic wave, and are one of the two main types of elastic body waves, so named because they move through the body of an object, unlike surface waves. We concatenated the frames into animations with the software. Types o fseismic waves p wave, s wave, surface wave. These waves are dispersive, meaning that different frequencies have different velocities. P and s waves are often called body waves because they propagate outward in all directions from a source such as an earthquake and travel through the interior of the earth. Explain that the amplitude of seismic waves is related to the amount of energy released from the source and decreases with distance from the. Learn vocabulary, terms, and more with flashcards, games, and other study tools. S, shear, secondary, transverse alternating transverse motions perpendicular to the direction of propagation, and the raypath. The first kind of body wave is the p wave or primary wave. The p wave, also called the primary wave, is the fastest seismic wave. P and s waves are signatures of fracture rock or earthquake. P waves are the first wave to hit the earth s surface.
Seismic waves can be longitudinal, transverse, or surface waves. Pwaves, swaves and surface waves flashcards quizlet. But it s the s wave that creates much of the aboveground shaking during an earthquake. Seismology and the earth s deep interior surface waves and free oscillations surface waves. Which waves are moving out first from the earthquake. The particles in a solid, through which a rayleigh surface wave passes, move in. The animations below illustrate both the propogation of the wave as well as the motion of particles as the wave passes. Surface wave on the other hand can only travel along the earth s surface and their amplitude decreases with depth into earth. Arendt for discussion of the earlier versions of the paper, and p. Also known as primary, compressional, or acoustic waves.
The main wave types are body waves p and s waves and surface waves rayleigh and love waves. They travel with velocities slower than s waves, and arrive later, but with much greater amplitudes. Body waves depart the point of origin at the same time, but p waves travel faster than s waves. P waves, also called compressional waves or primary waves, move through material by squeezing and stretching the material in the same direction as the wave is moving. It pushes and pulls the rock it moves through just like sound. Material returns to its original shape after wave passes. Apr 28, 2019 seismic waves can either be body waves or surface waves but the full story is far more complex. The event could easily be one of the most tragic natural disasters in recent history. Whereas body waves travel through a medium, surface waves.
The animation zooms in on the western us location of usarray seismometers as p, s, and surface waves sweep across the array. Video lecture on wave motions and speeds of three fundamental kinds of seismic waves. Earthquakes generate four principal types of elastic waves. The animations below demonstrate both types of wave and illustrate the. The main seismic wave types are compressional p, shear s, rayleigh r and love l waves. Earthquakes occur along a fracture in the earth s crust where one side moves relative to the other. Transverse horizontal motion, perpendicular to the direction of propagation and generally parallel to the earth s surface. S waves complement p wave imaging by contributing shallower reflectors, improved resolution, and structure imaging, where p wave imaging fails.
The seismogram shows the arrival times of the three generalized waves. Pwave motion incorporated research institutions for seismology. Some of the wave energy reflects off the boundary between the mantle and core. Survey design for p s surveys is similar to that of p waves, but must take into account the p s waves asymmetric raypath. P and s type waves are called body waves, since they are not confined to the surface. When p and s waves hit the surface they transform into surface waves. Smithsonian geologist elizabeth cottrell answers the main questions on smithsonian magazine s website. These are also the waves that are most easily felt during an earthquake and involve both updown and sidetoside motion. When a rayleigh wave travels, particles experience a backwardrotating motion that is in line with the waves direction. Earth can also be illustrated effectively using the simulation software seismic waves. P wave reflection seismic imaging is a robust method for near surface imaging. P waves are color coded go go green while s waves are colored red and surface waves are shown in yellow. Through the body of the earth these are called pwaves for primary because they are fastest and. The dynamic finite element software lsdyna was employed to verify the generation of s wave under finite vod.
While textbooks describe how p waves are faster than s waves that in turn are faster than surface waves, this animation of seismic waves generated by the mariana. Here we exaggerate the motion by bouncing a building to show what sensitive instruments record as seismic waves arrive at the station. Alternating compressions pushes and dilations pulls which are directed in the same direction as the wave is propagating along the ray path. The two main surface wave types are rayleigh waves, which have both compressional and shear motions, and love waves, which are purely shear. What forms when p waves and s waves hit the surface answers. Each wave has a characteristic speed and style of motion. A surface seismic wave generated by the interaction of p waves and s waves at the surface of the earth that move with a rolling motion. This sidetoside motion is in a horizontal plane roughly parallel to the earth s surface. The animations below illustrate both the propogation of the wave as well as the. P waves, or primary waves, are the first waves to arrive at a seismograph. Rayleigh waves do most of the shaking during a quake.
The world was shocked by the news of massive earthquakes and devastating tsunamis in japan. Primary wave, its velocity is faster than the other two types of waves. P s surveys use conventional sources but have several times more recording channels. P, s, and surface waves seismic waves can either be body waves or surface waves but the full story is far more complex. P waves in a liquid or gas are pressure waves, including sound waves. As a love waves passes, particles experience a sidetoside motion that is perpendicular to the waves direction. It travels through solid, liquid, and gas we know this because it is able to travel through the outer core which is liquid. The first of these waves to be detected is the p wave. Unlike pwaves, swaves cannot travel through the molten outer core of the earth, and this.
Surface wave components are love waves and reyleigh waves. An evaluation of numerical approaches for s wave component simulation in rock blasting. Longitudinal and transverse wave motion penn state acoustics. Seismic waves earthquakes discovering geology british. Examine p and s waves moving through earths interior.
Ocean with p, s, and surface waves traveling in all directions away from the epicenter. The parallel application of both methods is mutually beneficial and, thus, it is our favorable choice. The p wave can move through solid rock and fluids, like water or the liquid layers of the earth. They have larger amplitudes and do most of the shaking. Energy is released and travels through the earth in the form of seismic waves. These are the waves that cause the most damage because they are largest, and they are most clearly felt because they travel along the earth s surface. Discern between body and surface waves, primary and. Surface wave, rayleigh and love, propagation animations. The richter magnitude scale provides a measure of the intensity of earthquakes on a 1 to 10 base10 logarithmic scale. There are two basic types of wave motion for mechanical waves. Surface waves travel along the ground, outward from an earthquake s epicenter. An introduction to seismic waves university of nevada.
View the rayleigh wave animation below b as a love waves. The s wave which is a transverse body wave and the rayleigh wave which is a surface wave that causes surface material to move in ellipses normal to the direction of wave. Love and rayleigh waves are surface waves and propagate. Rayleigh waves are those experienced by witnesses who say they felt as if they were in the ocean. The p waves travel with the fastest velocity and are the first to arrive. In seismology, swaves, secondary waves, or shear waves are a type of elastic wave and are one of the two main types of elastic body waves, so named because they move through the body of an object, unlike surface waves. Particle motion consists of alternating compression and dilation. Animation to characterize behavior of three seismic waves. Generally smaller and higher frequency than the s and surface waves. P waves are compressional meaning that they shake parallel to the direction of propagation, travel faster than s waves, and can pass through the earth s core.
These waves are of a higher frequency than surface waves. Interpretation of s waves can allow determination of rock properties such as fracture density and orientation, poisson s ratio and rock type by crossplotting p wave and s wave velocities, and by other techniques. They are the energy that travels through the earth and recorded on seismographs. Surface waves are the result of p and s waves interacting with the surface of the earth. S waves travel slower than p waves in a solid and, therefore, arrive after the p wave.