Exam 3 - Geol 101 - pt 2

Chapter 9 – Earthquakes

• Epicenter vs focus

  • epicenter: point on the earth’s surface directly above the surface.

  • focus: point within the earth where the earthquake originates

• Seismic waves

  • P (Primary) waves; body waves

    • fastests, weakest, compressional waves, can go through solid, liquids and gases

  • S (Secondary) waves; body waves

    • second fastest, up and down motion, second strongest, can only pass through solids

  • Surface

    • slowest, most destructive wave, up and down motion, does not go through the entire earth

  • Properties

• Magnitude and magnitude scales

  • richter scale measures the amplitude of the largest seismic waves.

  • does not do well measuring largest earthquakes

    • each unit = 32 fold increase in energy

      • 32 5 magnitude earthquakes = the same energy as 1 6 magnitude earthquake

  • Moment magnitude scale

    • better for large earthquakes

    • uses area and amount of slip to measure the earthquakes energy

  • difference in magnitude (size of earthquakes)

    • subtract the magnitudes; make difference the exponent of 32

• Intensity and intensity scale.

  • intensity scale is the modified mercalli intensity scale

    • 12 divisions using roman numerals

    • may not reflect true size as it does not take many factors into account

• Earthquake hazards includes:

  • ground shaking, fires, landslides, avalanches, tsunami, flooding

• Building designs and how they affect earthquake damage

  • big buildings need a good support on the bottom

  • 3-4 story buildings have resonance that can be matched with the EQ waves causing them to collapse

• designs and how they affect