Waves, Faults, Reduction Programs

• Body Waves

  • Travelling through the interior of the earth, body waves arrive before the surface waves emitted by an earthquake.
• Body Waves

  • These waves are of a higher frequency than surface waves.
• PRIMARY Waves

  • The first kind of body wave is P wave or primary wave.
• Primary Waves

  • This is the fastest kind of seismic wave, and, consequently, the first to arrive at a seismic station.
• Particles move in the same direction that the wave is moving in, which is the direction that the energy is travelling in, and is called the direction of wave propagation.
• P waves can move through solid rock and fluids, like water or the liquid layers of the earth.
• Secondary Waves

  The second type of body wave is the S wave or secondary wave, which is the second wave you feel in an earthquake.
• Secondary Wave

  • is slower than a P wave and can only move through solid rock, not through any liquid medium.
• Surface Waves

  Travelling through the crust, surface waves are of a lower frequency than body waves, waves, and are easily distinguished on a seismogram as a result.
• Love Waves

  The first kind of surface wave is called a Love wave, named after A.E.H. Love, a British mathematician who worked out the mathematical model for this kind of wave in 1911.
• Love Waves

  It's the fastest surface wave and moves the ground from side-to-side.
• Rayleigh Waves

  The other kind of surface wave is the Rayleigh wave, named for John William Strutt, Lord Rayleigh, who mathematically predicted the existence of this kind of wave in 1885.
• An ACTIVE FAULT is a fault that has moved within the last 10,000 years. It shows evidence or has documented history of its recent movement.
• A TRENCH is the deepest portion on the sea floor. It is a manifestation of subduction zone where a tectonic plate moved or is pushed under another tectonic plate.
• Normal fault Geologic fault in which the hanging wall has moved downward relative to the footwall. Normal faults occur where two blocks of rock are pulled apart, as by tension.
• Strike-slip fault A fault in which surfaces on opposite sides of the fault plane moved horizontally and parallel to the strike of the fault.
• Thrust or reverse fault

  Geologic fault in which the hanging wall has moved upward relative to the footwall. Reverse faults occur where two blocks of rock are forced together by compression.
• Most commonly used methods of reducing earthquake risks:

  1.) Effective recording and interpretation of ground motion

  2.) Seismic Hazard Maps

  3.) Developing resistant structures