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• Hypocenter or focus


  The primary source of force from underneath the earth's surface
• Epicenter


  The point parallel to the focus at the surface
• Ground Shaking


  • One of the most notable effects of the energy from the focus
  • Mostly affects the concrete structures on the surface
  • The energy is transmitted in the form of seismic waves
• Measurement of an earthquake's intensity

  Depends on the waves' velocity, acceleration, frequency, and duration
• 1. waves or compressional waves


  The first waves to cause high-frequency vibrations in structures
• 1. waves or shear waves


  • The second waves to cause high-frequency vibrations
  • Due to its nature, S-waves cause a structure to vibrate from side to side
• Surface waves (Rayleigh and Love waves)


  Arrive last and cause only low-frequency vibrations
• Ground ruptures or fissures

  • Also referred to as tension cracks
  • A phenomenon where ground movement occurs and the surface of the ground breaks
  • Most commonly present in areas located or along the fault lines
• Zones of weakness


  • Locations which are predetermined to have ground rupture primarily due to the presence of faults
  • Called Zones of Weakness because underneath them is an impending ground rupture waiting to occur if ever the area encounters an earthquake