  The location underground where an Earthquake begins is the focus.  The crust breaks at the focus, and the released energy pushes outward in all directions in the form of seismic waves.  The point on Earth’s surface above the focus is the epicenter. Energy from earthquakes travels through the Earth

  Primary (P waves): travel the fastest and arrive first. They can travel through any layer.  Secondary (S waves): travel more slowly than primary waves and arrive second. Cannot travel through the mantle.  Surface waves : travel on the surface of the crust and cause the most damage. They arrive last.  rchives/year/2002/2002_11_03_waveani.php 3 types of seismic waves

  A seismograph is an instrument used to detect and record ground movementsseismograph  When an earthquake occurs, the shaking of the ground is recorded on paper Seismic Waves can be measured

  Earthquakes are the most unpredictable natural disaster  Magnitude Scales are used to describe how much energy an earthquake releases.  Shaking of the ground can cause landslides and buildings may sink or slide due to liquefaction, which causes soil to act like liquid Earthquakes can cause severe damage

  Scientists study the elevation of the ground and the movement of the ground to monitor earthquakes  An active fault where earthquakes have not occurred in a long time is a seismic gap.  A gap can show a build up of stress and that an earthquake might occur soon. Scientists work to monitor Earthquakes

  Buildings should be firmly put on their foundation  Base isolators should be used to absorb the ground motion Structures can be designed to resist earthquake damage