Lecture 22 even more earthquakes

Chapter 10: Earthquakes (Part 3) IN-CLASS EXERCISE Observe the following objects as I drop them on the floor and answer the following questions: Objects: - Clay - Rubber Ball - Ice Cube Questions: 1) Which of these behaves as a brittle material? 2) As a ductile material? 3) As an elastic material? 4) Which of these material properties best accounts for the generation of earthquakes? Optional extra credit assignment (20 pts): The just released movie “The Core” is loaded with geology, some of it accurate and some not! Assignment: Go and see “The Core” and write a report that separates geological fact from fiction! Length of write-up: pages Use illustrations Due two weeks from today TODAY’S LECTURE Detecting earthquakes Determining earthquake intensity and magnitude Locating earthquakes Earthquake damage (with examples) In summary: Types of seismic waves Motion produced by the different wave types P-wave S-wave Surface-wave Arrival times of earthquake waves Fig 10.17 W W Norton Seismology Seismology - The study of earthquake “waves”, earthquakes, Earth seismic waves Ancient Chinese seismograph Instrument to record seismic waves Seismogram - Recording of ground shaking from seismographs Fig 10.15 Seismograph vs seismogram W W Norton Electrostatic device: Fig 10.16 W W Norton For measuring vertical motion… For measuring horizontal motion… San Francisco 1906 Earthquake: Magnitude 8.3 San Fernando, CA 1971 Fig 10.32b U.S Geological Survey Ruptured gas main EQ Magnitude: 6.6 Death toll: 65 Earthquake Destruction Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design Other undesirable effects: 1) Landslides 2) Liquifaction of sediments Fire (rupture of gas lines) 4) Tsunamis (seismic sea waves) Tsunamis (Seismic Sea Waves) Tsunamis are often called tidal waves, but they are caused by seafloor earthquakes, not the tides! Travel at speeds of several hundred km/hr Wave heights