Why do seismic waves travel a curving path through the Earth? Refraction For background on this animation series, download Background from the Resources box.Animations are available for preview in embedded YouTube. To download, right click the 'Quicktime Animation' link and choose 'Save Target As' (PC) or 'Download Linked File' (Mac).Send us feedback. Travel times through different media This animation shows what happens to seismic waves as they encounter a boundary between a slower and faster layer in the Earth with introduction to Snell’s Law. Quicktime Animation (4 MB) Seismic Sprint—race to the seismometer The animation on the left describes the relative speeds of the direct, critically refracted and head waves. Quicktime Animation (1 MB) Seismic Sprint—graphing the seismograms Using the same seismic ray paths, the animation below adds a graph to see how data recorded show the distance transition of first arrival wave paths. Quicktime Animation (3 MB) Direct ray races 5 different refracted rays Quicktime Animation (2 MB) Quicktime Animation (3 MB)
Earthquakes - Q-files Encyclopedia Many earthquakes take place where one tectonic plate slides down beneath in another in what is called a subduction zone. Shock waves are sent out in all directions when, deep under the ground, the locked plates suddenly "give". A subduction zone How an earthquake happens The outer layer of the Earth is made up of a number of giant slabs, called tectonic plates. P- and S-waves travelling through the Earth's interior Shock waves The sudden jolt of a quake usually lasts no more than a few minutes and may be over in just a few seconds. P-waves (1) squeeze and stretch the rocks. P-waves (1) and S-waves (2) Shock waves radiate from the epicentre like ripples on a pond. There are different types of shock waves. Customers in a cafe experience an earthquake. Effects of a quake The shock waves hurtling through the crust cause the ground to shake. A road cracks open along a fault line, with one side slipping down a few centimetres. A road cracks open along a fault line. Unstable ground After an earthquake
How do P & S waves give evidence for a liquid outer core? Shadow Zones For background on this animation series, download Background from the Resources box.Animations are available for preview in embedded YouTube. To download, right click the 'Quicktime Animation' link and choose 'Save Target As' (PC) or 'Download Linked File' (Mac).Send us feedback. Intro to Shadow Zones The seismic shadows are the effect of seismic waves striking the core-mantle boundary. Quicktime (5.73 MB) Seismic Shadow Zones vs Light Shadows The wave properties of light are used as an analogy to help us understand seismic-wave behavior. Quicktime (9.36 MB) Shadow Zone Rollover Flash interactive rollover shows the different P and S phases and their respective shadow zones. Flash (154 kB) P Phases and the Shadow Zone Animation addresses 5 common variations of P-type seismic body waves. Quicktime (6.31 MB) S Phases and the Shadow Zone Animation addresses 3 common variations of S-type seismic body waves. Quicktime (4.49 MB) Please send feedback to Jenda Johnson.
Earthquakes And Tsunamis Almost every year, a large earthquake occurs somewhere in the world and captures the public's attention. Meanwhile, every day thousands of smaller tremors often go unnoticed by most people. Although we usually consider the ground to be solid and stable, the earth is, in fact, constantly shifting under our feet. What causes earthquakes? Earth's crust ranges from 3 to 45 miles deep (5 to 70 kilometers). As they slide past one another, the tectonic plates snag on rough patches of rock. An earthquake occurs when the pressure built up along a fault becomes stronger than the pressure holding the rocks together. Even though the tectonic plates slide at a regular rate over time, the way that faults release stored energy is different with each earthquake, said Shimon Wdowinski, a geophysicist at the University of Miami's Rosentiel School of Marine & Atmospheric Sciences. Tsunamis If the earthquake occurs in the ocean, it can push up powerful waves, known as tsunamis. Measuring earthquakes
Modeling Earthquake Waves | Earth Science Week An earthquake occurs when massive rock layers slide past each other. This motion makes enormous vibrations, which travel from the site of the earthquake in waves. The waves (seismic waves) travel all the way through the Earth. Seismologists can record these waves when they reach Earth’s surface using seismographs. Earthquakes generate three kinds of waves: Compressional waves (P waves) travel the fastest. Materials Two Slinkys™Flat, smooth surfaceNotebook and penSafety goggles Procedure Work with a partner. Earthquake Facts And Figures 29 November 2010 What are earthquakes? New Zealand lies on the boundary of the Pacific and Australian tectonic plates. Tectonic plates are large plates of rock, about 100km in thickness, that make up the foundation of the earth's crust and the shape of the continents (like pieces of a giant jigsaw puzzle). Tension builds up as they scrape over, under or past each other. Most (though not all) earthquakes occur at faults, which are breaks extending deep within the earth, caused by the movement of these plates. The fault that caused the Canterbury earthquake on 4 September 2010 has been named the Greendale Fault. Scientists from the Institute of Geological and Nuclear Sciences (GNS) think it is the first time this fault has moved in several thousand years, and it is unlikely that it will move again for another few thousand years. Measuring earthquakes In 1935 the American seismologist Charles Richter invented a scale to indicate the strength of an earthquake. Aftershocks Figure 1. Figure 2.
Sound Uncovered: An Interactive Book for the iPad Explore the surprising side of sound with Sound Uncovered, an award-winning interactive collection from the Exploratorium featuring auditory illusions, acoustic phenomena, and other things that go bump, beep, boom, and vroom. Hear with your eyes, see with your ears, test your hearing, make and modify recordings—this app puts you at the center of the experiment. Why do some noises seem louder at night? And it's free! Sound Uncovered won the Jackson Hole Science Media Symposium's 2014 Best Online and Interactive Media Award; the American Association of Museum's 2013 Silver MUSE award, Mobile Applications; and Museum and the Web's 2013 Best of the Web Award, Mobile.
Shaking Intensity It is a modern human tendency to focus on the number of an earthquake—specifically, the magnitude, or what people used to call the “Richter scale.” But the destruction from a quake usually has more to do with location and timing. Such was the case with the earthquake in Christchurch, New Zealand, on February 22, 2011. A September 2010 earthquake centered 40 kilometers (25 miles) west of Christchurch, in the plains near Darfield, struck at 4:35 a.m., had a magnitude of 7.1, and caused some structural damage and one death (by heart attack). The natural-color image above was captured on March 4, 2011, by the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite. The deeper the red color of the circle, the more intense the “peak ground acceleration,” or shaking of the earth. There are two forms of energy that cause the shaking in an earthquake. ReferencesGeoNet (2011, March 4) Christchurch badly damaged by magnitude 6.3 earthquake. Instrument(s):