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
EARTHQUAKES PowerPoint Presentation Outline Notes What Is An Earthquake? A wave-like vibration Travels away from a point of sudden energy release Focus is the point of sudden energy release Epicenter is located at the earth’s surface immediately above the focus What Causes Earthquakes? Most earthquakes are caused by faults Volcanoes Atomic explosions Elastic Rebound Theory 1906 earthquake Strain built up along strike-slip fault Earthquakes - sudden release of energy Called elastic rebound theory Horizontal slippage Some faults are locked Where Do Earthquakes Occur? Most earthquakes occur in linear belts 80% occur around the Pacific Ocean Basin Plate boundaries Bay Area Faults San Andreas transform fault Two plates grind past each other Many branches off this fault system o Hayward o Rodgers Creek o Calaveras o Green Valley Potential For Bay Area Earthquakes Are we overdue for an earthquake? 67-70% risk in 30 years Which Parts Of The United States Are Vulnerable To Earthquakes? Southwest including California Pacific Northwest Yellowstone Area How Are Seismic Waves Recorded? Seismographs record seismic waves Pen stays relatively still due to inertia of heavy mass Rotating drum moves with the ground vibration Seismic Waves Body waves move through the earth’s interior P (primary) waves move fastest o Compressional S (shear) waves move more slowly o Shake up and down Seismograms Record Vibrations 30. P Waves 31. S Waves 32. L or Surface Waves travel slowly o Most dangerous Seismograms Locate Epicenters Difference in arrival time between P and S waves can determine distance from epicenter Three or more stations are needed to determine the epicenter How Are Earthquakes Measured? Richter scale measures the magnitude of energy released at the focus o Open-ended scale - logarithmic increase o Richter 3 to Richter 4 is 30 X Modified Mercalli scale measures the intensity of an earthquake according to damage observed o Scale I-XII What Determines the Amount of Damage in an Earthquake? Magnitude and duration of the earthquake Underlying geology Building construction Effects of Earthquakes Ground Shaking Fault Rupture and Uplift Liquefaction Dam Breaks Landslides Tsunami Aftershocks Fire Where is the Safest Place to Live? Liquefaction Loose sand and mud turns into quicksand as groundwater rises Heavy objects sink in and light objects pop out Bayfill such as Emeryville and Alameda South Shore is vulnerable What Causes a Tsunami? Movement of the ocean floor Why Is a Tsunami Dangerous? A tsunami travels at over 800 kmh in open water Slows down and piles higher and higher in shallow water 30 meter high waves swamp the coast