Lesson 4 Potential Earthquake Hazards

• an earthquake, also called "shock", generates weak to strong shaking due to movement of rock material underneath

  Cramer (1991)
• Hays (1981) waves are classified to 3:

  1.)P waves or compressional waves

  • the first waves to cause high-frequency vibrations in structures; same direction

  2.)S waves or sheer waves

  • second waves; cause a structure to vibrate side-to-side

  3.)Surface waves (Rayleigh and Love waves)

  • arrive last and low-frequency vibrations
• main shock -> smaller magnitude earthquake experienced after the first one is called aftershocks
• • also referred as ground ruptures or fissures
  • ground movement occurs and surface of ground breaks

  Tension cracks
• Tsunami other term is harbor wave
• the waves increase their height while wavelength decreases

  Amplification Process
• • final stage of tsunami
  • refers to the approach of the tsunami's leading wave to the shore

  Runup
• described Landslides - mass movement of rock, soil, debris down a slope due to gravity


  PHIVOLCS (2021)
• Ex. of various triggers to landslides:

  • Rainfall
  • weathering of rocks
  • man-made activity (excessive mining)
  • natural triggers (plant, animal movement)
• Triggers that create conditions in an area that make it prone to landslides:

  • Steep slopes - increases potential energy of the impending landslide
  • Weakening of slope material - unstable landmass
  • Weathering of rocks - alteration of rock condition over time
  • Overloading on the slope - may be brought by man made development
• The hazard map for tsunamis is straightforward