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Transcript of Earthquakes
When stress that pulls rocks apart causes one fault plane to slide down against another fault plane. Type of Faults Reverse Faults:
When stress that presses rocks together causes one fault plane to move up against another fault plane. Strike-slip Fault:
When stress that pushes blocks horizontally causes one fault plane to slide sideways against another fault plane on either side of the fault plane. Fault Vocabuary Seismic Waves: Generated by the release of energy during an earthquake. They travel through the earth like waves travel through water. Focus: The place where the rock breaks, Usually located within 65 km of the Earths surface; however, some have been recorded at depths of 700 km. Body Waves: Seismic waves that spread outward from the focus in all directions. Epicenter: The location on Earths surface directly above the focus. Surface Waves: Seismic waves spread outward from the epicenter to the Earths surface. These waves move slower than body waves. Surface Waves: Seismic waves that spread outward from the epicenter to the Earths surface. These waves move slower than body waves. Primary Wave (P wave): also known as Compressional Waves that moves like a slinky. Secondary Waves (S-wave): also known as Transverse wave that move like a waving rope. How does energy travel though Earth? When a sudden break or shift occurs in the earth's crust, the energy radiates out as seismic waves, that travels through earth in Seismic waves. Seismic waves are made when the rock in the crust breaks, releasing enormous amounts of energy. The reason the rock breaks is over periods of time, the energy builds up and suddenly releases. The energy released moves out in all directions from the focus. The focus is the place where the rock breaks. There are two main types/ways/directions that Seismic Waves can move out:
*Body waves go outward from the focus in all directions.
*Surface waves spread outward from the epicenter to the Earths surface. Surface Waves can move rock particles in a rolling motion that not a lot of structures can stand, that therefore makes them the strongest waves. They destroy or damage anything that gets caught in their way. They also move slower than body waves, and therefore arrive last at recording stations. They make the ground roll up and down or from side to side. There are 2 types of Body Waves:
Primary Waves, waves that travel in the same direction the waves move.
And Secondary Waves, waves that travel perpendicular to the wave movement. Secondary waves are half the speed of Primary Waves. Secondary waves are slower moving, most of the time 2-5 km per second. They are caused by a shearing motion, which is waves that try to change the form that they are going though. They also arrive at recording stations second, right after Primary Waves. Reaching at recording stations second means that they reach any particular location on Earth's surface second after an earthquake. Secondary Waves cannot pass through liquids and fluids, because liquid cant shear. However they can pass through rock. Primary Waves travel at speeds that are very fast. Most of the time 6-7 km per second, and they arrive at recording stations first. Meaning, they reach any particular location on Earth's surface first after an earthquake, That therefore makes Primary Waves the fastest waves. Primary Waves can also pass through anything. Fun Facts
* Both types of Seismic waves start at the same time, but since one is slower, they reach at different times. Sort of like lightning and thunder.
* There are other waves that weren't written, they are called: Rayleigh waves, Love waves, and Stoneley waves.
* Pri= First. Good way to remember which wave starts first (Primary). Seismograph: is an instrument that constantly records ground movement produced by seismic waves at the seismographs location. Seismogram: A recording produced by a seismogram. Seismic Station is a laboratory that has equipment that can detect, monitor and record earthquakes. Interferogram: are a photographic record of light interference patterns. seismographs Seismic Waves are measured with seismographs. A seismograph is an instrument that constantly records ground movement produced by seismic waves at the seismograph’s location. There are two type of Seismographs, one that measures side-to-side movements and another that measures up-and-down movements. The ones that measure side-to-side movements has a heavy weight hanging from a wire. The weight stays still as the ground beneath it moves back and forth, a pen that is attached to to the weight records the movement on a drum. As for the one that measures up-and-down movements, it also has a heavy weight but on this one the weight is hanging from a spring. As the ground beneath it moves, the weight stays still as the spring absorbs the movement by getting longer or shorter. A pen is also attached to the weight, and it records the changes of distance between the ground and the weight. Seismographs record the frequency, duration, and amplitude of seismic waves in an earthquake, that also depends on how the recording of the earthquake seismogram looks like. A recording of an earthquake looks like bunch of scribbles in a line, the higher or closer a scribble is, the bigger and stronger the wave is at that seismographs location. Earthquake waves also decrease in strength as they travel through the earth. Scientists not only use seismographs to record earthquakes, they also use them to study seismograms. A seismogram is a recording produced by a seismogram. By studying seismograms, scientists can find the strengths and locations of earthquakes. To locate the epicenter of an earthquake scientist need to have three or more seismograms from three or more seismic stations (A seismic station is a laboratory that has equipment that can detect, monitor and record seismic activity.). Then they need to follow three steps. First they have to find the difference between the arrival times of the primary waves and secondary waves at each of the three stations. Next they need to find out the time difference that is used to determine the distance of the epicenter from each station. The greater the difference in time the farther away the epicenter is. Lastly, a circle is drawn around each station, with a radius corresponding to the epicenters distance from that station. The point where the three circles meet is the epicenter. Even though scientists know all this information, they still don't know how to predict earthquakes, but they might just be on the road. A team of scientists at NASA's Jet Propulsion Laboratory, in Pasadena, California, has made a new imaging technology that could lead to predicting earthquakes. They have the first airborne image of an earthquake. Interferogram images, which are a photographic record of light interference patterns, it shows colorful pictures of lines in butterfly-patterned lines and dots in different colors. The maps were collected from an aircraft with a radar antenna on it. The pilots had been making measurements over the area in southern California since the spring of 2009. Scientists aren't doing forecasting of earthquakes yet. It might take years of observation and years of studying earthquakes. But scientists are pretty confident that we can improve the current hazard maps, and bridges and dams, so they're more earthquake safe. Earthquake Damage Vocabulary Richter Scale - A numerical scale for expressing the magnitude of an earthquake on the basis of seismograph oscillations. liquefaction- the conversion of a solid or a gas into a liquid. An example is frozen thick soup that is heating up to a liquid. Aftershock- A smaller earthquake following the main shock of a large earthquake. Soil Liqefaction Example What are the damages from earthquakes? What are the damages from earthquakes? Earthquakes are very strong when they reach a magnitude of 5.0 or higher. A magnitude is an earthquake measuring scale. A 0-3.9 is a minor earthquake, a 4-4.9 does slight damage. a 5-5.9 is moderate and does some destruction, a 6-6.9 is an earthquake is a strong earthquake and does major damage to structures. A 7-7.9 is a major earthquake and well built structures are going to be destroyed. And the last, 8-10 are the greatest earthquakes and cause damage or destroy anything in there way. This scale is called the Richter Scale. An earthquake measuring 4 is enough to crack plaster and is felt. An earthquake measuring 5 vibrates strongly, shaking the earth, so it damages chimneys and weak buildings. An earthquake measuring 6 is an earthquake is strong enough to badly damage average buildings. An earthquake measuring 7 is an earthquake strong enough to destroy well-built structures. An earthquake measuring 8 will badly damage special earthquake-resistant buildings. An earthquake that measures 9 or above will destroy everything in its way. Earthquakes can damage the earth by liquefying soil and other loose materials. Its called liquefaction, its a process in which shaking of the ground causes soil to act like a thick liquid, like soup. It only happens in areas where the soil is made of sand and silt and contains a large amount of water. Because of liquefaction, buildings sink into the dirt and some collapse. All earthquakes have an aftershock. An aftershock is a smaller earthquake that follows a more powerful earthquake in the same area. Aftershocks usally have smaller magnitudes than the main earthquake. If an aftershock's magnitude is greater than the main earthquake, the aftershock is switched as the main earthquake and the original main earthquake is switched to a foreshock. Aftershocks are dangerous because they are usually unpredictable, can have a large magnitude (they cant be higher than the main earthquakes magnitude.), and can collapse buildings that are damaged from the main earthquake. Bigger earthquakes have more and larger aftershocks. Foreshock- a tremor preceding an earthquake. 9.5 Earthquake 7 Earthquake 4 Earthquake Guess The Earthquake Magnitude! When you see a picture, guess the earthquake magnitude - then press next to see if you were right! How Many Did You Get Right? What is a Tsunami and what destruction does it create? A tsunami is a extreme tidal wave triggered by an earthquake, volcanic eruption, or landslide, that submerges into land. Most tsunamis are caused by underwater earthquakes, but not all underwater earthquakes cause tsunamis. An earthquake has to be over about magnitude 6.75 to cause a tsunami. A tsunami may not be one single wave, but they may be several waves that can have different heights and can arrive at different hours apart. Tsunamis travel fast, almost thousands of kilometers without weakening. In deep water they can travel at speeds of about 700 kilometers per hour, and they can be up to one meter high. As a tsunami reaches shallow water around land, it slows down. However its height greatly increases.
As tsunamis make there way into shallow water, the the wave height can increase by over 10 times. Tsunami heights vary greatly along a coast. The waves can become bigger by shoreline and sea floor features. A large tsunami can flood low-lying coastal land over a mile from the coast. The largest tsunami was 1720 feet tall. Tsunamis travel fast, almost thousands of kilometers without weakening. In deep water they can travel at speeds of about 700 kilometers per hour, and they can be up to one meter high. As a tsunami reaches shallow water around land, it slows down. However its height greatly increases. Tsunamis destroy or damage buildings, And cause injuries. Since tsunamis come from the sea, they will wash fishing boats and other boats like cruise ships onto shore. The boats will be stuck on shore and might be wrecked from the forces of the wave. The waves will also cause fish to be washed onto shore and die. They can also flood the lands near the shore, causing people to die from them. This will damage the crops and cause nearby buildings to collapse. Some people might be trapped under the buildings. They uproot trees too, causing them to fall on houses and people. They also cause economic problems beacause they have to spend a lot of money rebuilding the houses and restoring what used to be. They would also face a decrease in tourism. Tsunami: is a extreme water wave triggered by an earthquake, volcanic eruption, or landslide. Landslide-The sliding down of a mass of earth or rock from a mountain or cliff. Underwater Earthquake- A submarine, undersea, or underwater earthquake is an earthquake that occurs underwater at the bottom of a body of water. Damage: Physical harm caused to something in such a way as to impair its value, usefulness, or normal function. tidal wave: an unusually high sea wave that is triggered especially by an earthquake. Farlex. "WordNet Search." The Free Dictionary. Farlex.Inc, 2013. Web. 4 Jan. 2013 <http://www.thefreedictionary.com/normal+fault>
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