Earthquakes and Tsunamis

• Epicenter


  Point on the ground directly above the hypocenter
• Hypocenter


  Location where the slippage or movement took place
• Intensity


  Measure of the amount of damage caused by an earthquake

  
• Magnitude


  Measure of the amount of energy released by an earthquake
• Active fault


  Fault where movement or slippage is expected to occur, marks areas prone to earthquakes, forms clear breaks in soil layers

  
• Inactive fault


  Fault that has ceased activity for a long time, does not disturb or break all the soil layers
• Elastic limit


  Threshold of stress that rock can hold before undergoing deformation, as rocks surpass this they release stored potential energy
• Fault scarp


  Elevated surface caused by the movement of a fault
• Richter scale


  • Used to measure the magnitude of an earthquake

  
• Moment magnitude scale


  • Measures the force needed to generate the recorded seismic waves

  
• Modified Mercalli scale


  Measures the amount of energy of an earthquake based on property damage
• PHIVOLCS Earthquake Intensity Scale (PEIS)


  Similar to modified Mercalli scale, used in the Philippines

  
• Tsunami


  Harbor waves or waves that come into the bay from the ocean, generated when an earthquake occurs underwater
• Not all tsunamis are generated by underwater earthquakes, earthquakes within continents can also displace water and cause tsunamis
• Formation of a tsunami


  1. Earthquake occurs

  2. Vertical push uplifts water

  3. Wave starts
• Tsunami due to faults

  Most often generated by reverse or thrust faults, which require a vertical push to uplift the water and start a wave
•  Micro


  Less the 2.0, Only recorded by seismographs
• Minor

  2.0–2.9, 3.0–3.9
• Minor

  2.0–2.9

  • Felt by few

  3.0–3.9

  • Felt by few, objects may shake
• Light


  4.0-4.9, Most people feel it, objects shake or fall
•  Moderate


  5.0–5.9, Everyone feels it, poorly-built buildings may be damaged or destroyed
• Strong


  6.0–6.9, Widespread shaking, buildings damaged
• Major

  7.0–7.9, Widespread damage in most areas
• Great

  8.0–8.9

  •  Widespread damage in large areas 

  9.0–9.9

  •  Severe damage to buildings
• Massive


  10.0 and above, Not yet recorded
• Triangulation is a process by which earthquakes are mapped using several seismographs.
• Seismograph


  It is an instrument that is used to determine the strength of an earthquake.
• Moment Magnitude Scale

  • This scale measures the force needed in order to generate the recorded seismic waves.
• Moment Magnitude Scale

  • It is a measure of the amount of energy of an earthquake based on property damage
  • It is measured on the modified Mercalli Scale.

  PHIVOLCS provides a scale similar to modified Mercalli called PHIVOLCS Earthquake Intensity Scale.
• Indian Ocean Earthquake

  • happened in 2004 at the west of Indonesia
  • magnitude 9.3 earthquake that occurred underwater
  • caused by the collision of India Plate and Sunda Plate
  • killed more than 230,000 in the 11 coastal countries
• Japan Earthquake

  • happened in 2011
  • 9.0 magnitude earthquake in Sendai
  • caused the destruction of Fukushima power plant
• Moro Gulf Earthquake (Philippines

  • happened in 1976
  • caused by movement of the plates along the Cotabato trench
  • a total of 8,000 people died
• Magnitude measures the amount of energy released by an earthquake. This can either be measured using the Richter Scale or Moment Magnitude Scale.
• • Intensity measures the amount of damage caused by an earthquake. Some of the intensity scales include modified Mercalli Scale and PHIVOLCS Earthquake Intensity Scale or PEIS. 
• Earthquake is the shaking of the ground caused by the release of energy that forms breaks along rock masses, or simply faults. It can either have tectonic or volcanic origin.
• Earthquakes can have varying depths such as shallow, intermediate, and deep.