Robertson abstract evidence on the structure and composition of the earths interior comes from 1 observations of surface rocks, 2 geophysical data from earthquakes, flow of heat from the interior, the magnetic field, and gravity, 3 laboratory ex. How scientists use seismic waves to learn about the earth s interior. Earthquakes create seismic waves that travel through the earth. Use this to assess your knowledge of fundamental vocabulary discussed over the past 2 weeks. Observations of the propagation of seismic waves made on the earths surface make it possible to study the structure of the earth. Seismology and earth s interior there are two categories of earthquake waves. Using these data, you will draw a diagram that shows the. Recognize the importance of seismic waves in the study of the earths interior. When an earthquake occurs the seismic waves p and s waves spread out in all directions through the earths interior. Jan 16, 2008 seismic waves generated in earths interior provide images that help us to better understand the pattern of mantle convection that drives plate motions. Earthquake the study of seismic waves provides a complete picture of the layered interior. Traveling through the interior of the earth, body waves arrive before the surface waves emitted by. On opposite sides of a fault line, forces in the earth attempt to move different portions of the crust in opposite directions. This release of energy causes intense ground shaking in the area near the source of the earthquake and sends waves of elastic energy, called seismic waves, throughout the earth.
Seismic velocity how fast earthquake waves travel through rocks depends on the composition of material and pressure. Seismic waves travel more quickly through denser materials and therefore generally travel more quickly with depth. From the study of seismic wave refraction and reflection, scientists infer earths internal structure by locating boundaries, or discontinuities, in its composition and physical properties. Seismograph stations measure the energy released by these earthquakes, but there are two that scientists are most interested with in regards to understanding the interior of the earth. The relation between the propagation velocity of p and s waves and depth figure 3 has made it possible to identify a series of structural shells in the earth. The most important information on the constitution of the earths interior has been obtained from studies of seismic body waves longitudinal and transverse seismic waves propagating through the earth.
The change at 400 km is probably produced by a polymorphic transition of olivine. For the love of physics walter lewin may 16, 2011 duration. Body waves can travel through earth inner layers while surface waves can travel only on the surface of the land. Sep 03, 2015 for the love of physics walter lewin may 16, 2011 duration. Seismic waves one ingenious way scientists learn about earths interior is by looking at how energy travels from the point of an earthquake. Waves of energy that travel through the earths layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large manmade explosions. G3earths interior upsc iasseismic wavesprimary,secondary. Seismic waves and the layers of the earth three hundred years ago the famous scientist isaac newton calculated, from his studies of planets and the force of gravity, that the average density of the earth is twice that of surface rocks and therefore that the earths.
Seismic waves and the earths interior as we discussed in class, earthquakes occur when two portions of earth crust move with respect to each other. This article is about waves that travel through the earth. The division of the earth into the earths crust, mantle and core, the later division into socalled bullen zones, or the latest laterally. Earthquakes and the earth s interior earthquakes earthquakes occur when energy stored in elastically strained rocks is suddenly released. And were going to focus on one more than the other. We have already discussed the main elements in earth s interior, the core, the mantle, and the crust. Seismic waves and the layers of the earth edinformatics. Seismology and earths interior there are two categories of earthquake waves. Seismic stations located at increasing distances from the earthquake epicenter will record seismic waves that have traveled through increasing depths in the earth. A the focus of the earthquake is directly below the epicenter. Show full abstract waves produced were situated on the earths surface within a circle round the epicentre of each source.
Seismology and earths interior body waves can travel deep. A formula used to describe the relationship between the angles of incidence and refraction as they pass through a boundary between different media. 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. Now, theres two fundamentally different types of the seismic waves. The scientific study of the earths interior structure is enabled by the utilization of two types of energy waves. We can use the behavior of seismic waves to tell us about the interior of the earth. Waves of energy that travel through the earth s layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large manmade explosions. Using seismic waves to study earths interior in this lab, you will be given a table that shows the thicknesses of different layers in earths interior and the average speed of seismic waves as they travel through these layers. The ambient seismic noise that makes earth hum could help scientists map the planets interior, from the crust, through the mantle and possibly to the core. Seismic waves and earths interior introduction when you look at a seismogram the wiggles you see are an indication that the ground is being, or was, vibrated by seismic waves. Using seismic waves to image earths internal structure. The two main types of waves are body waves and surface waves. Importance of understanding the interior of the earth understanding the structure of the earths interior crust, mantle, core and various forces heat, seismic waves emanating from it is essential to understand the evolution of the earths surface, its current shape and its future.
Body waves traveling through the interior of the earth, body waves. Primary waves also called p waves are fastest, traveling at about. How scientists use seismic waves to learn about the earths interior. Earthquakes are definitely a geologic hazard for those living in earthquake prone areas, but the seismic waves generated by earthquakes are. Earths interior and seismic waves activity 1 graphing seismic waves scientists know that seismic waves travel about 1 kms through solid rock. There are two kinds of body waves, and two kinds of surface waves. The most important information on the constitution of the earth s interior has been obtained from studies of seismic body waves longitudinal and transverse seismic waves propagating through the earth. In this case, were talking about the surface of the ground. Using these data, you will draw a diagram that shows the physical layers of earth and the. Earthquakes radiate seismic energy as both body and surface waves. Many earthquakes happen because of stress on local areas of rock. For ocean waves sometimes called seismic sea waves, see tsunami.
This is an inquirybased student exercise designed to explore how we use seismic waves to understand the structure of the earth s interior. Seismic waves, shadow zone of pwaves and swaves pmf ias. While some of the waves occur on the surface, other waves of energy move through the planet at very deep levels. Seismic waves and earths interior penn state earthquake. This is a list of vocabulary used throughout content statement 1. Earthquakes and the earths interior tulane university. By analyzing these seismic waves, seismologists can explore the earth s deep interior. Differentiate the different types of seismic waves. Seismic waves are waves of energy that travel through the earths layers and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large humanmade explosions. Pdf seismic surface waves in laterally inhomogeneous earth. Seismic waves generated in earths interior provide images that help us to better understand the pattern of mantle convection that drives plate.
Within the mantle there are two zones, at depths of 400 and 670 km, where small jumps in seismic wave speed produce seismicwave reflections. Seismic tomography of the earths interior article pdf available in american scientist 725 september 1984 with 342 reads how we measure reads. Body waves traveling through the interior of the earth, body waves arrive before the surface waves emitted by an earthquake. The division of the earth into the earth s crust, mantle and core, the later division into socalled bullen zones, or the latest laterally. An earthquake in simple words is shaking of the earth. It is caused due to release of energy, which generates waves that travel in all directions.
Seismic waves can also be critically refracted at an interface when refraction reaches 90. Using seismic waves to image earths internal structure request pdf. The two major types are body waves s and p waves and surface waves. List the key observations that revealed earth to possess a. The scientific study of the earth s interior structure is enabled by the utilization of two types of energy waves. Nov 26, 2012 the ambient seismic noise that makes earth hum could help scientists map the planet s interior, from the crust, through the mantle and possibly to the core. Seismic waves generated in earths interior provide images that help us to better understand the pattern of mantle convection that drives plate motions. Using seismic waves to image earths internal structure nature. Seismic waves article about seismic waves by the free. Earths interior read earth science ck12 foundation.
Seismic body waves can be refracted and reflected just as sound and light waves are. When energy is released, waves of motion like the effect of a pebble tossed into a pond are set up in the earth. This is based on the velocity of the waves, meteorites, mass of the earth and other lines of evidence. Just as the prism below refracts light at its faces, seismic waves bend, reflect and change speed at the boundaries between different materials below the earths surface2. Pdf refraction why do seismic waves travel a curving path. This is an inquirybased student exercise designed to explore how we use seismic waves to understand the structure of the earths interior. Earths interior travel times in a constant velocity earth constantvelocity. Earthquakes occur when energy stored in elastically strained rocks is suddenly released. From seismic tomography, first introduced in the late 1970s refs 1, 2, we now have a good understanding of the firstorder characteristics of the longwavelength 1,0002,000 km threedimensional elastic structure of earths. Modeling of seismic waves traveling through the earth allowed seismologists to determine that the core begins at a depth of 2900 km, or in other words, the mantle is 2900 km thick. Discover how scientists learn about earth s interior using seismic waves, meteorites, density, and the magnetic field. Earthquakes and the earths interior earthquakes earthquakes occur when energy stored in elastically strained rocks is suddenly released. Earths hum helps probe planets interior earths layers. By analyzing these seismic waves, seismologists can explore the earths deep interior.
Primary waves also called pwaves are fastest, traveling at about. Surface waves can only travel very near the surface of the earth. The large earthquake that triggered the tsunami of 2004 sent waves of energy through much of the planet. Now, there s two fundamentally different types of the seismic waves. Seismic velocities depend on the material properties such as composition, mineral phase and packing structure, temperature, and pressure of the media through which seismic waves pass.
Discover how scientists learn about earths interior using seismic waves, meteorites, density, and the magnetic field. Dec 01, 2019 importance of understanding the interior of the earth understanding the structure of the earths interior crust, mantle, core and various forces heat, seismic waves emanating from it is essential to understand the evolution of the earths surface, its current shape and its future. To learn about earths interior, scientists use energy to see the different layers of the earth, just like doctors can use an mri, ct scan, or xray to see inside our bodies. Just as the prism below refracts light at its faces, seismic waves bend, reflect and change speed at the boundaries between different materials below the earth s surface2. This fact sheet uses data from the 1994 magnitude 6. This quiz and worksheet combination will help you test your understanding of how. Study of the propagation of mechanical energy released by earthquakes. We have already discussed the main elements in earths interior, the core, the mantle, and the crust.
Seismic waves travel outward in all directions from where the ground breaks at an earthquake. By studying the propagation characteristics travel times, reflection amplitudes, dispersion characteristics, etc. Seismic waves and the layers of the earth three hundred years ago the famous scientist isaac newton calculated, from his studies of planets and the force of gravity, that the average density of the earth is twice that of surface rocks and therefore that the earth s interior must be composed of much denser material. If earth is made entirely of solid rock with the same density seismic waves should travel at a consistent speed through earths interior to its core.
Now, surface waves are ones that literally travel across the surface of something. Modeling the interior of the earth using seismic waves. Describe the characteristics of seismic waves and explain the difference between primary waves, secondary waves, and surface waves. The refraction or reflection of seismic waves is used for research into the structure of the earths interior. Explain the elastic rebound theory, which provides an explanation for the origin of earthquakes.