Earthquakes are one of the planet's most dangerous natural forces. They originate in the crust of the Earth which is a thin layer of a depth of aroundbelow the surface. Below the crust is a thick layer of molten rock, which is solid but can move due to high heat and high pressures. The Earth's outer core lies beneath the mantle, is mostly fluid and surrounds a solid inner core. Earthquakes are caused when volcanoes erupt or when tectonic plates in the Earth's crust are in relative motion with each other. This causes a seismic wave on the surface of the Earth which can be violent enough to destroy the land and buildings.
Definition of seismic waves
It is clear that earthquakes cause disturbances in the Earth and these disturbances carry energy through the Earth to areas away from the point where the earthquake occurs.
Earthquakes are carried by waves that move through the Earth, basically using the Earth as a medium, transferring large amounts of energy in the process. These waves are called seismic waves.
In this article, we will learn about the different types of seismic waves and the energy that is carried by each.
Types of seismic waves
The crust of the Earth is solid rock and lies directly beneath the continents and the oceans. The crust is separated into plates that can sometimes move against each other with large amounts of friction occurring between them. This friction can lead to vibrations (disturbances) in the crust which is the source of seismic waves. Seismometers are instruments that can be used to measure the magnitudes of earthquakes by producing a seismogram which can be read to determine the amplitude and intensity of the related seismic waves.
We will discuss four seismic wave types that differ in how they propagate energy and the media through which they move. These seismic waves can be separated into two broader groups; body waves and surface waves. Body waves are seismic waves that travel through the inner layers of the Earth, whereas surface waves travel only along the Earth's surface. From the definition of the seismic wave, both surface and body waves carry energy through the Earth.
Types of seismic waves: P-waves
The first type of seismic wave that we will study is the P-wave. P-waves or primary waves are usually the first waves to be felt when an earthquake occurs. This is because P-waves travel the fastest of all waves generated by an earthquake. P-waves are body waves since they move along the inner layers of the Earth with a speed of aboutin water andin granite. P-waves can travel through both solid ground and water and travel through the inner core, outer core and mantle.
P-waves are also longitudinal waves. That is, the material of the medium, through which a P-wave passes, will vibrate parallel to the direction in which the wave is travelling. P-waves do not have large amplitudes and so their effects on the ground are not severe and generally do not cause much damage. Due to their longitudinal nature, P-waves cause material to compress and expand as they move through the medium.
Longitudinal waves are waves in which the vibrating particles move in the same direction as the direction of propagation of the wave.
Types of seismic waves: S-waves
Secondary waves or S-waves are seismic waves that travel at speeds of about 50% to 60% of the speed of the primary waves. Their effects are hence only felt after the effects of the P-waves during an earthquake. S-waves are also classified as body waves as they move along the inner layers of the Earth. S-waves waves cannot travel through water and can only travel through solid material and hence travel through the mantle only.
S-waves are transverse waves. This means that the material of the medium moves from side to side while the wave moves perpendicularly to the motion of the material. S-waves have an amplitude that is greater than P-waves and their effects are felt more severely and can cause greater damage. S-waves cause shear in the material of the medium of propagation.
Shear is caused when adjacent surfaces move parallel to each other but in opposite directions.
Transverse waves are waves in which the vibrating particles move perpendicular to the direction of propagation of the wave.
Types of seismic waves: Rayleigh waves
Rayleigh waves are seismic waves that travel at speeds of 80% to 90% of the speed of S-waves. The effects of these waves are usually felt shortly after the S-wave has passed. Rayleigh waves are created by a combination of transverse and longitudinal motion. The material of the Earth moves along circular paths whilst the wave itself propagates in a direction that is perpendicular to the plane of these circles.
The effects are much more dangerous than primary and secondary waves since Rayleigh waves are classified as surface waves. The circular nature of the motion of surface material means that the ground moves up and down as the Rayleigh wave moves. This means that they carry all their energy along the Earth's surface and can cause a large degree of shaking and damage.
Types of seismic waves: Love waves
Love waves are the last of those that are seismic. They travel slower than S-waves or P-waves but slightly faster than Rayleigh waves. Love waves are transverse and the material of the Earth's surface moves perpendicular to the direction of wave motion, with an amplitude that is parallel to the surface. Love waves are classified as surface waves and their energy can be immediately transferred to buildings and objects on the ground. Love waves can cause the greatest destruction and damage outside of the epicentre of an earthquake.
The epicentre of an earthquake is the point on the Earth's surface directly above the point of origin of the earthquake.
Seismic Wave Diagrams
The diagram below shows the compressions and rarefactions of P-waves which are consistent with longitudinal waves. We can see that the materials vibrate in the same direction as the wave's motion.
A depiction of a primary seismic wave (P-wave) in which the particles oscillate in a direction that is parallel to the direction of wave motion (left to right). P-waves can travel through solids and liquids, adapted from image by Davezelenka CC BY-SA 4.0
The diagram below shows the transverse nature of S-waves that has materials vibrating in a direction that is perpendicular to the direction of motion of the wave. S-waves and P-waves travel beneath the surface of the Earth.
A depiction of a secondary seismic wave (S-wave) where the particles oscillate perpendicular (up and down) to the direction of wave motion (left to right). S-waves can travel through solids only, adapted from image by Davezelenka CC BY-SA 4.0
The following image depicts a Rayleigh wave that contains properties of both longitudinal and transverse waves, with materials moving in circular paths in planes perpendicular to the direction of wave motion.
An illustration of a Rayleigh seismic wave where the materials vibrate in circles that are in planes perpendicular to the direction of the wave's motion. Rayleigh waves are more dangerous than P-waves and S-waves, Wikimedia Commons CC 1.0
The Love wave is shown in the diagram below and indicates that the wave is transverse, with the material moving perpendicular to the direction of propagation of the wave. The amplitude of the material is parallel to the surface. Love waves and Rayleigh waves travel on the surface of the Earth.
A diagram of a Love wave that shows the direction of the vibrating material to be perpendicular to the direction of wave motion. The amplitude of the wave is parallel to the Earth's surface, Wikimedia Commons CC 4.0
Seismic Waves - Key takeaways
- Earthquakes originate in the Earth's crust and are caused when plates of the Earth's crust move relative to each other.
- Waves that carry energy away from the earthquake are called seismic waves.
- Seismometers can be used to measure the magnitudes of earthquakes.
- P-waves are longitudinal body waves that can travel through solid ground and water.
- P-waves are the fastest seismic waves and travel faster in solids than in water.
- P-waves do not cause significant destruction.
- S-waves are transverse body waves that can only travel through solids.
- S-waves travel slower than P-waves.
- S-waves can cause greater damage than P-waves due to their greater amplitude.
- Rayleigh waves are surface waves that contain a combination of longitudinal and transverse motion.
- Rayleigh waves travel slightly slower than S-waves.
- Rayleigh waves cause significant destruction.
- Love waves are transverse surface waves.
- Love waves travel slightly faster than Rayleigh waves.
- Love waves cause the most significant amounts of destruction.
FAQs
What are the types and definition of seismic waves? ›
Types of Seismic Waves
The two main types of waves are body waves and surface waves. Body waves can travel through the Earth's inner layers, but surface waves can only move along the surface of the planet like ripples on water. Earthquakes send out seismic energy as both body and surface waves.
There are three basic types of seismic waves – P-waves, S-waves and surface waves. P-waves and S-waves are sometimes collectively called body waves.
What is a seismic wave quizlet? ›Seismic waves - what is the full definition? vibrations that travel through Earth carrying the energy released during an earthquake. Three types of seismic waves are P waves, S waves, and surface waves.
What are the different types of seismic waves How do they differ quizlet? ›- primary waves. -body wave. -push-pull. -particles move parallel to wave direction. ...
- secondary waves. -body waves. -side-to-side (typical wave) -particles move perpendicular to wave direction. ...
- surface waves. -particles move through surface in circular motion. -slowest, most destructive. wave travels ON Earth.
Seismologists use seismic waves to learn about earthquakes and also to learn about the Earth's interior. The two types of seismic waves described in “Plate Tectonics,” P-waves and S-waves, are known as body waves because they move through the solid body of the Earth. P-waves travel through solids, liquids, and gases.
What are the 5 types of seismic waves? ›There are three major kinds of seismic waves: P, S, and surface waves. P and S waves together are sometimes called body waves because they can travel through the body of the earth, and are not trapped near the surface. A P wave is a sound wave traveling through rock.
What is a seismic wave? ›Earthquake waves, more often called seismic waves, are vibrations generated by earthquakes that continue to spread within Earth or along its surface. Earthquakes generate two main types of waves: body waves, which travel inside Earth, and surface waves, which travel on the surface.
What are the types of waves? ›Waves come in two kinds, longitudinal and transverse. Transverse waves are like those on water, with the surface going up and down, and longitudinal waves are like of those of sound, consisting of alternating compressions and rarefactions in a medium.
What type of wave is P wave? ›P Waves. P waves are compressional waves that do not produce much damage. They can move through any type of material and travel at almost twice the speed of S waves. High frequency P waves do not weaken, or "attenuate," as rapidly as S waves so they retain higher frequencies when they arrive at seismic stations.
How are P waves and S waves different? ›P waves can travel through liquid and solids and gases, while S waves only travel through solids. Scientists use this information to help them determine the structure of Earth. For example, if an earthquake occurs on one side of Earth, seismometers around the globe can measure the resulting S and P waves.
What are primary and secondary waves? ›
Primary (P) and secondary (S) waves are two types of waves caused by earthquakes. They are defined based on when they arrive and are felt on the surface. P waves, or primary waves, arrive first while S waves, or secondary waves, arrive second. Both waves cause the ground to shake when an earthquake occurs.
What are seismic waves answer in one sentence? ›Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. Therefore, seismic waves are caused by earthquakes. It is the energy that travels through the earth and is recorded on seismographs. Q.
What are the three main types of seismic waves? ›Seismic waves can either be body waves or surface waves -- but the full story is far more complex. Generally speaking, there are two types of waves: body waves (which comprise of P or Primary waves and S or Secondary waves) and surface waves (Love and Rayleigh).
Is a seismic wave a sound wave? ›As the Earth shakes at the surface, seismic waves are pulsing through the layers of Earth below, invisible to human eyes and ears but observable as sound waves.
What are the different characteristics of seismic waves? ›Seismic waves can be distinguished by a number of properties including the speed the waves travel, the direction that the waves move particles as they pass by, where and where they don't propagate. We'll go through each wave type individually to expound upon the differences.
What type of seismic wave travels the slowest? ›They are called surface waves, as they diminish as they get farther from the surface. They travel more slowly than seismic body waves (P and S).
Which type of wave does the most damage? ›Surface waves are the seismic waves that cause the most damage. Surface waves are named as such because they move along close to the surface of the Earth. Some waves can move side-to-side, causing a twisting action in the ground. These are called Love waves.
How does a seismic work? ›As the name suggests, seismic examines surface-induced seismic pulses to image subsurface formations. Basically, a seismic wave is generated underneath the earth's surface, and then picked up by sensors called "geophones" as the waves bounce off subsurface formations - that is, layers of rock beneath the surface.
How seismic waves are measured? ›A seismograph is the primary earthquake measuring instrument. The seismograph produces a digital graphic recording of the ground motion caused by the seismic waves. The digital recording is called a seismogram. A network of worldwide seismographs detects and measures the strength and duration of the earthquake's waves.
What are seismic waves 7? ›Seismic waves are created by the abrupt movement of elements within the Earth, such as fault slips during an earthquake. Seismic waves can be caused by volcanic eruptions, explosions, landslides, avalanches, and even flowing rivers.
What is the first type of seismic waves? ›
P Waves. The first kind of body wave is the P wave or primary wave. It's the fastest kind of seismic wave, and the first to arrive at a seismic station. P waves can move through solid rock and fluids, like water or the liquid layers of the Earth.
What are the 2 types of body waves? ›Body waves are of two types: Primary waves (also called P-waves, or pressure waves) and Secondary waves (S-waves, or shear waves). P-waves are compression waves. They can propagate in solid or liquid material.
Are seismic waves ocean waves? ›Tsunami is a Japanese word meaning 'harbor wave', and is sometimes called seismic sea wave or, erroneously, tidal wave. Tsunamis are usually small and barely noticed in deep ocean, but become large and cause damage when they approach coasts or harbors.
Are earthquakes called seismic waves? ›Explain to students that earthquake energy travels in the form of waves. These waves are called seismic or earthquake waves. There are different kinds of earthquake waves: body waves and surface waves. Body waves pass through the interior of the Earth whereas surface waves travel along the Earth's surface.
What frequency are seismic waves? ›[3] From seismometric data we know that earthquakes generally radiate seismic waves mainly in the frequency range of 0.01 to 10 Hz, even if they can generate higher frequencies.
What is the best definition of a wave? ›Webster's dictionary defines a wave as: a disturbance or variation that transfers energy progressively from point to point in a medium and that may take the form of an elastic deformation or of a variation of pressure, electric or magnetic intensity, electric potential, or temperature.
What type of wave is light? ›1. Light as a wave: Light can be described (modeled) as an electromagnetic wave.
What are the 6 types of waves? ›Micro Waves, Radio Waves, Infrared Rays, Ultraviolet, Visible Light, Gamma Rays and X rays, are the prime E.M wave varieties.
What is P wave and T wave? ›'P' wave is the first wave in an ECG and is a positive wave. It indicates the activation of the SA nodes. 'T' wave too is a positive wave and is the final wave in an ECG though sometimes an additional U wave may be seen. It represents ventricular relaxation. The p wave is also called the atrial complex.
What are P and R waves? ›The P-wave, PR interval and PR segment
The P-wave reflects atrial depolarization (activation). The PR interval is the distance between the onset of the P-wave to the onset of the QRS complex. The PR interval is assessed in order to determine whether impulse conduction from the atria to the ventricles is normal.
What is a body wave? ›
Body waves are solutions of the elastic equation of motion that propagate outward from a seismic source in expanding, quasi-spherical wave fronts, much like the rings seen when a rock is thrown in a pond. The trajectory along which the elastic energy propagates is called a ray.
How do S waves travel? ›S-wave : The S-wave (secondary, shear, or side-to-side wave) is slower than the P wave and arrives next, shaking the ground up and down and back and forth perpendicular to the direction it is traveling. Shear waves travel at 3.8 kilometers (2.4 miles) per second.
Which type of wave is faster? ›Answer and Explanation: Electromagnetic waves always travel faster than mechanical waves. This is because electromagnetic waves travel at the speed of light and are not dependent on physical matter to propagate, meaning they can move through a vacuum.
How does the S waves move? ›S waves shake the ground in a shearing, or crosswise, motion that is perpendicular to the direction of travel. These are the shake waves that move the ground up and down or from side to side. S waves are called secondary waves because they always arrive after P waves at seismic recording stations.
What are secondary waves called? ›S waves also called secondary waves and shear waves, are the second waves to hit the seismographs. They are transverse waves, which means that the motion is perpendicular to the direction of wave propagation.
Why is it called primary wave? ›P waves are seismic body waves meaning that they travel through the Earth's interior. The name primary waves stems from the fact that they are normally the first waves recorded by a seismograph. P waves typically travel at velocities of 6–7 km/s in the Earth's crust and at higher velocities in the mantle.
What does S waves stand for? ›In S or shear waves, rock oscillates perpendicular to the direction of wave propagation.
What is seismic in a sentence? ›Earthquakes produce two types of seismic waves. The latest seismic activity was also felt in northern Kenya. I have never seen such a seismic shift in public opinion in such a short period of time.
What are seismic waves an example of? ›transverse wave, motion in which all points on a wave oscillate along paths at right angles to the direction of the wave's advance. Surface ripples on water, seismic S (secondary) waves, and electromagnetic (e.g., radio and light) waves are examples of transverse waves.
What are seismic waves and how do they travel through the Earth? ›Seismic waves travel a curving path through the earth due to changes in composition, pressure, and temperature within the layers of the Earth. Seismic waves travel at different speeds through different materials. In this 2-layer model two wave fronts leave an impact at the same time but the lower layer is faster.
What are the 2 main types of seismic waves and which causes more damage? ›
S waves are more dangerous than P waves because they have greater amplitude and produce vertical and horizontal motion of the ground surface. The slowest waves, surface waves, arrive last. They travel only along the surface of the Earth.
What are the two types of seismic waves and which type is most destructive? ›Seismic waves can be classified into two basic types: body waves which travel through the Earth and surface waves, which travel along the Earth's surface. Those waves that are the most destructive are the surface waves which generally have the strongest vibration.
Can seismic waves travel through gas? ›S waves cannot travel through liquids or gases. That's because the types of stresses set up by those waves can only be transmitted through solid materials.
What is the best definition of seismic wave? ›seismic wave, vibration generated by an earthquake, explosion, or similar energetic source and propagated within the Earth or along its surface.
How are P-waves and S waves different? ›P waves can travel through liquid and solids and gases, while S waves only travel through solids. Scientists use this information to help them determine the structure of Earth. For example, if an earthquake occurs on one side of Earth, seismometers around the globe can measure the resulting S and P waves.
What are 2 types of body waves? ›Body waves are of two types: Primary waves (also called P-waves, or pressure waves) and Secondary waves (S-waves, or shear waves). P-waves are compression waves. They can propagate in solid or liquid material.
How many types of waves are there? ›Waves come in two kinds, longitudinal and transverse. Transverse waves are like those on water, with the surface going up and down, and longitudinal waves are like of those of sound, consisting of alternating compressions and rarefactions in a medium.
How are seismic waves described? ›Seismic waves are propagating vibrations that carry energy from the source of the shaking outward in all directions. You can picture this concept by recalling the circular waves that spread over the surface of a pond when a stone is thrown into the water.
What is an example sentence for seismic waves? ›The best indicators that an explosion had occurred were the seismic waves that radiated from it and might be detected all over the world.
What is stronger P or S waves? ›S waves are more dangerous than P waves because they have greater amplitude and produce vertical and horizontal motion of the ground surface. The slowest waves, surface waves, arrive last. They travel only along the surface of the Earth. There are two types of surface waves: Love and Rayleigh waves.
Which waves travel faster? ›
P waves travel fastest and are the first to arrive from the earthquake. In S or shear waves, rock oscillates perpendicular to the direction of wave propagation. In rock, S waves generally travel about 60% the speed of P waves, and the S wave always arrives after the P wave.
Why is P wave the fastest? ›P waves, or Primary waves, are the first waves to arrive at a seismograph. P waves are the fastest seismic waves and can move through solid, liquid, or gas. They leave behind a trail of compressions and rarefactions on the medium they move through. P waves are also called pressure waves for this reason.