lecture 3 earthquake

• earthquake

  vibration induced in the earths crust due to internal or external causes that virtually shake up a part of the crust and all the structures and living and non living things existing on it
• seismology

  science dealing with the study of earthquake in all their aspects
• parts of earthquake

  • focus
  • epicenter
  • seismic waves
• focus (hypocenter)

  the point on a fault which the first movement or break occurs during an earthquake
• epicenter

  the point on the surface vertically above the focus of a particular earthquake
• seismic waves

  elastic waves generated at the focus. they travel in all directions with the velocities that determines how strong the earthquake is
• 3 main types of seismic waves

  • p waves
  • s waves
  • l waves
• p waves

  also called as primary waves, push and pull waves, longitudinal waves and compressional waves. these are the fastest waves.
• s waves

  secondary waves or shear waves, transverse waves or distortional waves.
• l waves

  long waves or surface waves, confined mainly to the near surface layers of the earth
• l wave types

  • love waves
  • rayleigh waves
• fault or faultline

  planar breaks in the rock along which there is displacement of one side relative to the other
• types of fault

  • strike slip fault
  • dip slip fault
• strike slip fault

  one along which the displacement is parallel to the strike
• dip slip fault

  one with which the displacement is vertical
• magnitude

  term expressing the rating of an earthquake on the basis of amplitude of seismic waves recorded as seismograms
• intensity

  also a term of expressing the rating of an earthquake in a qualitative manner, on the basis of its effect on living and non living things of the region it occurs
• classification of earthquakes

  • by depth of focus
  • by magnitude
  • by cause of origin