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
Faulting at Devils Slide | Lee Trampleasure's Blog The opening of the tunnel around Devil’s Slide in San Mateo County allowed for the creation of a mile-long trek to look at some of California’s fascinating geology. In my last geology hike to the trail, I took a photo of the great sedimentary layers at the north end of the trail, then edited the photo to show how well the strata line up on each side of a fault through the sediments. Mouse over the image below to see the image of the current conditions of the strata. Imagine the strata lined up like this years ago. After faulting After pressure and faulting, the strata now looks like this. The video below includes a great description of the geology of the area. More resources on the geology of Devil’s Slide: San Mateo County Parks: Devil’s Slide Trail (includes half-hour video)KQED Quest: The Rock’s of Devil’s Slide (March 2013)Civil + Structural Engineer: Devil’s Slide Tunnel (June 2013) Like this: Like Loading... Related Tentative geology road trip/hikes to Southwest, March 2016 July 7, 2015
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
QuakeFeed iPhone App 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.