earth science

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Compare and contrast primary, secondary and surface waves. Explain how an earthquake epicenter is located using seismic wave information Describe how seismic wave studies indicate the structure of Earth’s interior.

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Sudden movement along a fault releases energy that causes an earthquake. The point beneath Earth’s surface where the movement occurs is the focus of the earthquake

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generated by an earthquake, act like a slinky

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Waves that cause particles in the rocks to move back and forth in the same direction as the wave. Compression and stretching of slinky.

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Causes particles in the rocks to move at right angles to the direction of the wave. Up and down motion of a slinky.

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Particles move in an elliptical motion, as well as a back and forth swaying motion.

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Scientists use this information to locate the Epicenter. P waves travel the fastest S waves arrive second Surface waves are the slowest All reach seismograph stations The rule of thumb: the father apart the waves, the farther away the epicenter is. (similar to lightning and thunder)

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Seismic wave information is gathered at three seismograph stations. Scientists draw circles around each station on a map. The radius of each circle equals the station’s distance from the epicenter. The point where all three circles intersect is the location of the epicenter.`

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Determine the difference in arrival time between the primary and secondary waves at each station for each quake from the data table. Once you determine the arrival time fo seismic waves for each seismograph station, use the graph to determine the distance in kilometers of each seismograph from the epicenter of each earthquake.

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Using the string, measure the circumference of the globe. Determine a scale of centimeters of string to kilometers on Earth’s surface. (Earth’s circumference = 40 000 km) For each earthquake, place one end of the string at each seismic station location on the globe. Use the chalk to draw a circle with a radius equal to the distance to the earthquakes’ epicenter. Calculated distance to epicenter (km) from each seismograph location. New York Seattle Rio de Janeiro Paris 3425 3760 7700 9210

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Use string: measure circumference Proportion 100cm = 1cm 40000km n 2. Distance from epicenter: Quake A÷ by 400 Quake B ÷by 400 N = 400 3. Round your answers to nearest whole number. 4. End of string – location of station radius = distance to epicenter

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Primary waves travel at about 6km/s through granitic crust. The distance from Phoenix, Arizona to Los Angeles, California is about 600 km. How long would it take primary waves to travel between these two cities?

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about 100 seconds Most of you might think that all earthquakes begin at Earth’s surface. Earthquakes originate at the point where rocks break. This can occur near Earth’s surface or deep inside Earth’s crust, lithosphere, or asthenosphere.