earthquakes

• Earth


  Consists of different layers
• Crust


  • First layer of the earth
  • Made up of several large and small plates
• Mantle


  • Middle layer of the earth
  • Mostly made up of magma
  • Divided into upper mantle and lower mantle
• Core


  • Central layer of the earth
  • Divided into liquid outer core and solid inner core
• The movement of plates on the crust is often accompanied by earthquakes or volcanic eruptions
• Cause of earthquakes


  1. Crustal plates move and push towards each other or away from each other

  2. Nearby rocks break and slide past each other

  3. Waves of energy are released and sent out through the earth
• Seismograph


  Instrument that measures the motion of the ground during an earthquake
• Types of earthquakes


  • Volcanic earthquakes
  • Tectonic earthquakes
• Volcanic earthquake


  Shaking of the ground due to a strong volcanic eruption
• Tectonic earthquake


  Caused by the movement of the earth's crust or crustal plates, can occur above ground or beneath oceans
• Magnitude


  Refers to the amount of energy released by an earthquake from its focus
• Intensity


  Refers to the effect of an earthquake, especially the damages
• Magnitude is written in numbers with decimals, intensity is written by Roman numerals
• Focus


  The break in the ground caused by the pressure of the moving rocks, where the earthquake originates
• Epicenter


  The ground above the focus
• Richter scale


  Used to measure the magnitude of an earthquake, developed by Charles F. Richter
• Earthquake magnitude ranges


  • 0 to 1.9 - Only detected by seismograph
  • 2 to 2.9 - People may feel it, observe swinging objects
  • 3 to 3.9 - Comparable to vibration of a passing truck
  • 4 to 4.9 - May break windows, cause small objects to fall
  • 5 to 5.9 - May damage well-built structures, severely damage poor structures
  • 6 to 6.9 - May cause cracks in concrete walls, chunk of plaster and concrete may fall
  • 7 to 7.9 - Buildings may displace from foundations, cracks on earth's surface, some underground pipes may break
  • 8 to 8.9 - Bridges may be destroyed, only few structures left standing
  • 9 and above - Near total destruction
• The Philippines is frequently hit by earthquakes due to its location in the circum-Pacific belt or Pacific Ring of Fire
• Earthquake


  Tectonic plates hit, bump or slide past another plate
• Fault/Fault plane


  The surface where tectonic plates slip
• Hypocentre


  The place where the earthquake originates
• Epicenter


  The place on the Earth's surface where the earthquake occurs
• Convergent boundary


  • One plate is forced over another, causing a Thrust Fault
  • Many hills and mountains have been formed due to the Convergent Boundary
• Divergent boundary


  • Plates are drifted apart from each other, forming a Rift Zone
  • This gives birth to new ocean floors
• Transform fault


  • The plates slip by each other, also called Strike-Slip
• Earthquakes occur under water

  Causes a Tsunami
• Earthquakes are the shaking, rolling or a sudden shock of the earth's surface