Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Today’s Objective: What is an Earthquake? Do Now: Hand in Lab #17 – Seafloor Earthquakes – the vibration of Earth produced by the rapid release of energy. - Often caused by slippage along a break in the Earth’s crust. Vocabulary Epicenter The location on the surface directly above the focus Focus The point within the Earth where the earthquake starts and energy is released in all directions. Faults - are fractures in Earth where movement has occurred. (Earthquakes are usually associated with large fractures in the Earth’s crust and mantle.) San Andreas Fault California Cause of Earthquakes When there is movement along a fault stored energy is released. The vibrations of an earthquake as the rocks trying to return to their original state. When the strength of the rock is exceeded, it suddenly breaks, causing the vibrations of an earthquake. How are Earthquakes measured? • Seismology – the study of earthquake waves. • Seismographs – instruments that record earthquake waves. Seismograph Seismogram – a trace produced recording ground motion. Primary Waves (P–Waves / Compression Waves) • Are push-pull waves that push (compress) and pull (expand) in the direction that the waves travel. • Travel through solids, liquids, and gases. • Have the greatest velocity of all earthquake waves. Secondary Waves (S–Waves / Transverse Waves) • Shake particles at right angles to the direction that they travel. • Travel only through solids. • Slower velocity than P waves. Surface Waves (L- Waves) • Seismic waves that travel along the Earth’s outer layers • These are the most destructive earthquake waves • The ground moves up and down and back and forth ** A seismogram shows all three types of seismic waves – first - P waves then - S waves lastly - surface waves.** • P & S Wave Animation Closure: Why do most earthquakes cause little damage and loss of life? - Because most occur in areas that are not populated. L.A. Earthquake Earthquake Destruction