The body waves interact with the surface rocks and generate new set of waves called surface waves. Body waves: They are generated due to the release of energy at the focus and move in all directions travelling through the body of the earth.Earthquake waves are basically of two types - body waves and surface waves. Release of energy during earthquake generates waves which are called Earthquake Waves.How the P and S wave shadow zones form.Why the S waves don't move through the core.Watch this video, "Seismic Shadow Zones-Introduction to P & S wave shadow zones" by IRIS Earthquake Science. Sometimes it's helpful to visually see what's going on. Do this with thousands of earthquakes all over the planet over several years, a pattern starts to emerge. Because their energy gets absorbed by liquids, a large "S-Wave Shadow Zone" where no S-waves from the originating earthquake will be present. The refraction of the P waves creates what is called the "P-Wave Shadow Zone" where no seismic waves from the originating earthquake will be present. Image source: "shadow zone" by USGS is in the Public Domain The image below shows the paths each of the waves take as they travel through the Earth. While the composition and density haven't changed, we know that the inner core is solid because the P-waves refract again slightly and travel in a new direction. We also know that the inner core is solid using these same facts. P-waves refract and begin to travel in a new direction.Thus, we know where the mantle-core boundary is based upon the following: When waves transition from a medium with one set of conditions into another the waves will bend (or refract) and will start moving in a different direction. Thus the P and the S waves will travel in a straight path throughout the mantle.Īt the mantle-core boundary, there is a change not only in density but also in composition and phase the core is now a denser material, composed of metal, and is a liquid. will travel in a more-or-less straight path and at the same velocity so long as the conditions (density, composition, etc) remain unchanged. The P-waves and S-waves are the only ones that travel through the body of our planet. When an earthquake releases energy, all of the seismic waves are released at the same time. Image source: "Onde cisaillement impulsion 1d 30 petit" by Christophe Dang Ngoc Chan is licensed under CC BY-SA 3.0 Image source: "Onde compression impulsion 1d 30 petit" by Christophe Dang Ngoc Chan is licensed under CC BY-SA 3.0 Solids only - the wave's energy gets absorbed by liquids. There are two types - P waves and S waves. There are two basic types: body waves, which travel through the body of the Earth, and surface waves, that travel only along the surface of the Earth.īody waves are the ones scientists use to see inside the Earth. Seismic waves are generated by earthquakes, volcanic eruptions, or other things that go bump on the Earth's surface. The best set of tools scientists have are seismic waves. So, how do we know what’s down there? We can use a variety of tools to indirectly "see" inside the Earth, just like a doctor uses X-rays to "see" a broken bone. How Do We Know What’s Down There? P and S Wavesĭespite what Hollywood may tell you, we cannot drill down to the center of the Earth.
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