NATSCI4_Earthquakes

• Earthquake is a weak to violent shaking of the ground produced by the sudden movement of rock materials below the Earth’s surface.
• Identify the ff.

  A) Wave Fronts

  B) Fault

  C) Focus

  D) Epicenter

  E) Fault scarp

  
• Types of Earthquakes

  1. Volcanic quakes
  2. Tectonic quakes
• Volcanic quakes are earthquakes produced by movement of magma beneath volcanoes.
• Tectonic quakes are earthquakes produced by sudden movement along faults and plate boundaries.
• Faults are fractures in the Earth’s crust along which slippage or displacement has occurred or may occur again.
• Dip slip faults move along the direction of the dip plane and are described as either normal or reverse (thrust), depending on their motion.
• Strike-slip faults are when two blocks slide past one another.
• Elastic Rebound Theory discusses about the gradual accumulation and release of stress and strain.
• Seismology is the study of behavior of seismic waves.
• Identify this.

  A) Seismometer

  
• Identify this.

  A) Seismogram

  
• What are used to describe the strength of an earthquake?

  • Magnitude
  • Intensity
• Magnitude is calculated from seismic records and estimates the amount of energy released at the source.
• Richter Scale is used to measure an earthquake's magnitude.
• Intensity is the degree of ground shaking at a given locale based on the amount of damage.
• These are used to measure an earthquake's intensity.

  • Modified Mercalli Intensity Scale
  • PHIVOLCS Earthquake Intensity Scale
• PHIVOLCS Earthquake Intensity Scale

  I - Scarcely Perceptible

  II - Slightly Felt

  III - Weak

  IV - Moderately Strong

  V - Strong

  VI - Very Strong

  VII - Destructive

  VIII - Very Destructive

  IX - Devastating

  X - Completely Devastating
• These are types of earthquake hazards.

  • Ground rupture
  • Ground shaking
  • Liquefaction
• These are the secondary effects of earthquakes.

  • Landslides
  • Tsunamis
• Ground rupture is the deformation on the ground that marks, the intersection of the fault with the earth’s surface.
• Ground shaking is the disruptive up, down and sideways vibration of the ground during an earthquake.
• Liquefaction is the phenomenon wherein sediments, especially near bodies of water, behave like liquid similar to a quicksand.
• Landslide is the down slope movement of rocks, solid and other debris commonly triggered by strong shaking.
• Tsunamis are series of waves caused commonly by an earthquake under the sea.
• PHIVOLCS stand for Philippine Institute of Volcanology and Seismology.
• Tsunamigenesis explain how tsunamis work.
• Tsunamigenic earthquake events

  • 6.6 Manila Bay (November 9, 1828)
  • 7.5 Manay, Davao Oriental (November 11, 1921)
• Not all earthquakes generate tsunamis. (TRUE)
• All earthquakes generate tsunamis. (FALSE)
• Shallow earthquakes generate the most destructive tsunamis. (TRUE)
• Shallow earthquakes generate the least destructive tsunamis. (FALSE)
• Large tsunamis are likely to be generated by earthquakes with magnitude greater than or equal to 7.0 (TRUE)
• Large tsunamis are likely to be generated by earthquakes with magnitude less than or equal to 7.0 (FALSE)
• Structural damage due to earthquake vibrations depends on:

  • Wave amplitudes
  • Duration of vibrations
  • Nature of material upon which the structure rests
  • Design of structure
• Triangulation is used to locate the epicenter of an earthquake.