Earthquake

• earthquake - is a phenomenon that occurs without warning

  and involves violent shaking of the ground and everything over it.

  It results from the release of accumulated stress of the moving

  lithospheric or crustal plates
• Fault lines - are cracks on the Earth’s surface along with smaller

  plates move or slip against each other.
• Focus– the place where energy is released like an explosion
• Epicenter– the point that is immediately above the focus
• Active Fault– fault that has moved within the last 10,000 years.
• Magnitude – the measure of total energy released at the

  earthquake’s point of origin which is below the Earth’s surface.
• Seismograph– Instrument that measures magnitude
• Richter Magnitude Scale– used to measure the strength of an

  earthquake
• Intensity– the perceived strength of an earthquake based on the

  relative effect on people and structures on the Earth’s surface.

  Generally, the nearer an area is to the epicenter, the higher the

  intensity is felt in that area
• Ground Shaking– caused by passage of seismic waves beneath

  structures. As a result these structures may tilt, split, topple or

  collapse
• Ground Rupture– displacement of the ground due to the violent

  shaking of the surface
• Vertical displacement– one side of the ground goes up or down or

  both sides move with one side going up and the other going

  down
• Horizontal displacement– happens when there is a lateral

  movement from side to side, one side goes to the left or right, or

  both move sideways in different directions
• Liquefaction– takes place when there is an increase in water

  pressure in saturated soil because of ground shaking. Sand

  deposits become more compact and water is squeezed towards

  the surface which creates a condition similar to quicksand. This

  decreases the ability of the ground to support structures above it.
• Ground Subsidence– lowering of the land surface due to land

  extraction of ground water and natural gas, mining, and

  earthquakes.
• Tsunami– series of large waves resulting from the disturbance of

  sea water commonly due to an earthquake.
• Near-field (Local) Tsunami– can reach the shoreline within

  minutes
• Far-field (Distant) Tsunami– can take several hours to do the same

  as they may be generated from other countries