Disrred

• Fault


  A weak point in the tectonic plate where the pressure inside the crust is released
• Focus


  The area inside the Earth where an earthquake starts is known as the focal point. It is centered on the portion of the fault that has the greatest movement
• Epicenter


  The point at the Earth's surface directly above the focus. During an earthquake, the strongest shaking occurs at the epicenter
• Magnitude


  Measures the energy being released from the origin of the earthquake
• Seismograph


  Instrument measures the magnitude
• Richter Magnitude Scale


  Measures the quantity of seismic energy released by an earthquake
• Intensity


  The strength of the trembling made by the earthquake at a place
• Mercalli Scale


  Determines the intensity of an earthquake, which varies depending on where you are
• Active faults


  Areas along which displacement is expected to occur. Since a shallow earthquake produces displacement across a fault, all shallow earthquakes occur on active faults. These are considered to be geologic hazards
• Inactive faults


  Areas that can be identified but which do not have earthquakes
• Earthquake


  • Shaking off the ground caused by the movement of tectonic plates
  • Mostly occurs along the fault line
  • Can cause great damage to properties and life loss
• Various Potential Earthquake Hazards

  • Ground Shaking
  • Ground Rupture
  • Liquefaction
  • Ground Subsidence
  • Tsunami
  • Landslide
• Ground Shaking


  Vibration of the ground; triggers liquefaction & landslides
• Ground Rupture


  Offset of the ground
• Liquefaction


  Sand/soil & groundwater mixed
• Ground Subsidence


  Sinking/settling of the ground surface
• Tsunami


  Giant sea waves generated by an earthquake w/ a magnitude greater than 7.0
• Landslide

  Down a slope
• Deadliest: Indian Ocean (Sumatra Indonesia); Casualties: 350,000; Year: 2004
• Recognizing the Natural Signs of an Impending Tsunami

  1. Feel - shaking; magnitude greater than 7.0

  2. See - unusual sea-level fluctuation

  3. Hear - loud roaring
• Earthquake Hazard Map


  A special type of map that shows the possible physical & geographical effect of an earthquake w/in a particular area/region; known as ground shaking hazard map
• Ground shaking


  • Caused by the release of stored energy in the lithosphere that was released
  • Its strength is measured in terms of velocity, acceleration, frequency, and duration
• Primary Volcanic Hazards (Direct)

  • Lava Flow
  • Pyroclastic Density Current
  • Tephra Falls
  • Volcanic Gas
• Lava Flow

  Molten volcanic rock
• Pyroclastic Density Current


  Mixed volcanic rock fragments & hot gasses
• Pyroclastic flow


  Contact with ground
• Pyroclastic surge


  Move above ground
• Tephra Falls


  A shower of pyroclastic materials
• Tephra Falls

  • Ash - less than 2 mm in diameter
  • Lapilli - 2-64 mm in diameter
  • Blocks - greater than 64 mm in diameter
• Volcanic Gas


  Gas components of volcanic rocks that reacted with other elements in the environment which results to harmful chemicals
• Secondary Volcanic Hazards (Indirect)

  • Lahar
  • Debris Avalanches
  • Tsunami
• Lahar


  Mud flow
• Primary (Hot Lahar)


  Caused by pyroclastic materials reaching watersheds/eruption of a crater lake

  
• Secondary (Cold Lahar)


  Caused by heavy rains
• Debris Avalanches


  Result from the built up of volcanic debris
• Lava Flow


  • Least dangerous
  • Speed of 3km/day to 50km/h
  • Speed is determined by the lava's viscosity (resistance to flow), density, & local area's land features
  • Effusive eruption

  
• Tephra Fall

  • Plinian eruption - eruption column
  • Lapilli & blocks will fall relatively near the volcano
  • Ashes reaches father places
  • Large amount of ash is called ash fall

  
• Pyroclastic Density Current

  • Very dangerous phenomenon
  • Reach a temperature around 700 C
  • Travel with a speed of 100 km/h
  • Cause asphyxiation (death by suffocation) & incineration (death by burning)
• Volcanic Gas


  Less dangerous
• Lahar


  • Most deadly & destructive
  • Speed of 1.3 m/s to 40 m/s