4. measuring activity

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4. measuring activity

  1. 1. TECTONIC LANDSCAPES MEASURING MAGNITUDE
  2. 2. SPECIFICATION DETAIL• 3.1d The measurement of earthquake magnitude (the Mercalli and Richter scales).• Diagrams showing the characteristics of focus and epicentre.
  3. 3. LEARNING OBJETIVES• Know the differences between the Mercalli (intensity) and Richter (magnitude) scales.• Explain how earthquakes occur with reference to the epicentre and focus of earthquakes.
  4. 4. DEFINITIONS • Watch Seismograph: Here• Mercalli scale: (intensity)Uses seismic scale to measure the intensity of an earthquake. It isused to measure the effects of an earthquake.• Richter scale: (magnitude)A logarithmic scale used to express the total amount of energyreleased by an earthquake(It is a base 10 logrimithic scale: e.g. 5.0 on the Richter scale has ashaking amplitude 10 times larger than one that measures 4.0, )assign a single number to quantify the energy released during anearthquake.
  5. 5. HOW ARE EARTHQUAKES MEASURED?The Richter scale can beused to measure themagnitude (power) of atremor using aninstrument called aseismograph.It is a logarithmic scalewhich means that a size‘6’ earthquake on theRichter scale is 10 timeslarger than a size ‘5’ and100 times larger than asize ‘4’.
  6. 6. HOW DOES A SEISMOGRAPH WORK?
  7. 7. THE MERCALLI SCALEThe Mercalli scale rates an earthquakes magnitudebased on observations of the damage it causes on ascale of 1 to 12. Items shake from Buildings collapse: shelves: scale 5 scale 10
  8. 8. Richter ScaleIntensity Magnitude Observations (Mercalli)(Mercalli) (approx. comparison)I No effect 1 to 2II Noticed only by sensitive people 2 to 3III Resembles vibrations caused by heavy traffic 3 to 4IV Felt by people walking; rocking of free standing objects 4V Sleepers awakened; bells ring 4 to 5VI Trees sway, some damage from falling objects 5 to 6VII General alarm, cracking of walls 6VIII Chimneys fall and some damage to building 6 to 7IX Ground crack, houses begin to collapse, pipes break 7X Ground badly cracked, many buildings destroyed. Some landslides 7 to 8XI Few buildings remain standing, bridges destroyed. 8XII Total destruction; objects thrown in air, shaking and distortion of ground 8 or greater
  9. 9. TASK: SORTING• Using the following statements, sort them into which best describes the scales.• Here
  10. 10. Richter ScaleIntensity Magnitude Observations (Mercalli)(Mercalli) (approx. comparison)I No effect 1 to 2II Noticed only by sensitive people 2 to 3III Resembles vibrations caused by heavy traffic 3 to 4IV Felt by people walking; rocking of free standing objects 4V Sleepers awakened; bells ring 4 to 5VI Trees sway, some damage from falling objects 5 to 6VII General alarm, cracking of walls 6VIII Chimneys fall and some damage to building 6 to 7IX Ground crack, houses begin to collapse, pipes break 7X Ground badly cracked, many buildings destroyed. Some landslides 7 to 8XI Few buildings remain standing, bridges destroyed. 8XII Total destruction; objects thrown in air, shaking and distortion of ground 8 or greater
  11. 11. TASK: WATCH THESE CLIPS• Tachoma, Japan earthquake: Here• Chilean earthquake: Here• Kashima, Japan earthquake: Here• Tokyo, Japan earthquake: Here• Maryland, USA earthquake: HereWhich scale was the most easy to use? Why?
  12. 12. EXAM PRACTISE• Describe 2 differences between the Mercalli and Richter scale. (2 marks)One difference is …………A second difference is that……………
  13. 13. LEARNING OBJETIVES• Know the differences between the Mercalli (intensity) and Richter (magnitude) scales.• Explain how earthquakes occur with reference to the epicentre and focus of earthquakes.
  14. 14. EPICENTRE• Epicentre on google earth: here• Interactive : Here
  15. 15. EPICENTRE AND FOCUS
  16. 16. EXAM QUESTION• Outline a difference between the focus and epicentre of an earthquake. (2marks)
  17. 17. LEARNING OBJETIVES• Know the differences between the Mercalli (intensity) and Richter (magnitude) scales.• Explain how earthquakes occur with reference to the epicentre and focus of earthquakes.

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