science gr8 3rd qtr

• What is an earthquake?


  It is the shaking and trembling that results from the movement of rock beneath

  Earth’s surface.
• ROCKS are constantly subjected to deformation

  caused by pushing and pulling forces
• The movement is caused by STRESS in Earth's

  layers
• 3 Types of Stress

  Shearing, Tension, and Compression
• Shearing- stress that pushes a mass of

  rock into two opposite directions.
• Tension- pulls on the crust,

  stretching rock so that it

  becomes thinner in the middle.
• Compression-squeezes

  rock until it folds or breaks
• STRESS will result to SEISMIC WAVES
• Earthquakes always begin in rock below the surface
• “ELASTIC POTENTIAL

  ENERGY STORED IN ROCKS

  IS RELEASED
• FAULT - A fracture in the earth's crust that forms when the earth's crust is pushed upward
• FOCUS - or hypocenter, the point within earth where faulting begins
• Epicenter - point directly above the focus of a surface
• Where and How Earthquakes Happen?

  Earthquake happen along Tectonic Plate

  Boundaries
• Earthquakes can be caused by :

  1. Faults

  2. Plate boundaries

  3. Volcanic eruptions

  4. Human Activities
• Earthquakes caused by

  faults and by plate

  boundaries are called

  TECTONIC

  EARTHQUAKES
• ACTIVE FAULT


  There is an evidence that it has moved one or more times in the last

  10,000 years and may move again in the future.
• INACTIVE FAULT


  A fracture that has not experienced any geologic activity in the last

  10, 000 years or more
• DIP-SLIP fault- the movement is up or down and parallel to the dip of the inclined fault surface
• HANGING Wall- the block above the inclined fault surface
• FOOTWALL- the block below the inclined fault surface
• DIP- is the angle made by the fault plane with the horizontal
• NORMAL DIP-SLIP FAULT


  The hanging wall has moved

  downward relative to the footwall
• REVERSE DIP-SLIP FAULT


  The hanging wall has moved upward

  relative to the footwall
• STRIKE-SLIP fault-


  the movement or slip is horizontal and parallel to the strike of the fault
• OBLIQUE-SLIP fault-


  has both dip-slip and strike-slip
• Philippine Fault Zone-


  important tectonic and seismic feature that cuts

  across the Philippine Archipelago
• Valley Fault System

  dextral strike-slip type
• Seismic Waves-


  Seismic waves are caused by the sudden movement of materials within the Earth,
• Types of Seismic Waves

  Body Waves

  Surface Waves
• Types of Body Waves

  P waves travel faster than other waves are longitudinal waves, can pass through solid and liquid materials

  S waves- transverse waves, can pass through solid materials only
• Types of Surface Waves

  Rayleigh waves- move the direction of the wave similar to ocean wave

  Love Waves- moves like a heart
• Magnitude


  the energy released by an earthquake at the focus, recorded by an instrument called Richter Scale
• Seismograph is an instrument used to record seismic waves.
• PHIVOLCS - Philippine Institute of Volcanology and Seismology
• Earthquake Hazards

  Ground Shaking

  Liquefaction

  Landslide

  Ground rupture

  Tsunami