earthquake review

# earthquake review - Chapter 10 and Interlude C Earthquakes...

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Chapter 10 and Interlude C – Earthquakes and the Earth’s Interior 1. What is an earthquake? Ground-shaking caused by the sudden release of strain energy caused by rock rupture (faulting) Are earthquakes common? Almost 1 million detectable earthquakes happen every year Where is most of the Earth’s seismic energy released? Tectonic stresses What are the 3 types of strain? Compressive, tensile, shear How do stress and strain differ? Stress is force exerted per unit area, Strain: deformation caused by stress Why do faults move in a “stick-slip” style? The faults aren’t perfectly aligned thus as the faults start to shift they get caught causing stress which builds up. What happens when rock strength is exceeded? The rock snaps when the crust breaks sliding suddenly occurs on a fault generating vibrations 2. What are the two types of body waves? Compressional or Primary (P) waves and Shear or Secondary (S) waves How do they differ in terms of speed, motion, and types of material that they can pass through? P waves: Push-pull (compress and expand) motion Travel through solids and liquids and gases Fastest S waves: Shaking motion Travel only through solids; not liquids slower How do surface waves differ from body waves? Body waves pass through the interior of the Earth while surface waves travel along the Earth’s surface 3. How do we use seismic wave travel speeds to locate the epicenter of an earthquake? The difference in velocity and therefore arrival time of the different kinds of earthquake waves provide the key. P-waves and S-waves pass through the interior of the Earth at different velocities. The farther the waves travel the greater the distance between them. Seismologists use the time delay between the arrivals at a seismograph station of the P and S waves for the calculation. The delay between the P wave and S wave arrival times increases as the distance from the epicenter increases. We can represent this time delay on a graph with a line called a travel-time curve, which plots the time since the earthquake began on the vertical axis and the distance to the epicenter on the horizontal axis. How do we measure magnitude? Using the Richter scale: amplitude of ground motion, increasing one order in magnitude = 10-times increase in amplitude, normalized for distance. Moment magnitude scale: amount of strain energy released, based on fault displacement How much energy is released during an earthquake? It depends on the magnitude of the earthquake. A magnitude 6 earthquake releases about the same energy as the first atomic bomb.

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## This note was uploaded on 07/30/2008 for the course GEOL 110 taught by Professor Centorbi during the Summer '08 term at Maryland.

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earthquake review - Chapter 10 and Interlude C Earthquakes...

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