EARTHQUAKES & SEISMIC WAVES

EARTHQUAKES

SEISMIC WAVES

BRACE YOURSELVES

FOCUS & EPICENTER

• seismic wave goes in every direction from earthquake's focus
• point on surface directly above the focus is called the epicenter

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TYPES OF SEISMIC WAVES

P WAVES

• compress and expand like an accordion
• can move through solids or liquids

S WAVES

• can vibrate side to side or up and down
• can move through solids, but not through liquid

SURFACE WAVES

• move more slowly than P or S waves
• movement is similar to waves in water
• can make the ground roll like the ocean

MODIFIED MERCALLI SCALE

• I-III: Little to no damage
• IV-VI: Slight damage
• VII-IX: Moderate to heavy damage
• X-XII: Massive destruction

RICHTER SCALE

• uses seismograph to measure & record wave magnitude
• moment of magnitude used to rate the total energy an earthquake releases

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FINDING THE EPICENTER

• use seismic waves to find it
• use data from thousands of seismograph stations

MONITORING EARTHQUAKES

SEISMIC DATA

• 2004: scientists in USArray project place 400 seismographs across Western U.S.
• Every month, 18 seismographs are moved east

SEISMOGRAPH

SEISMOGRAMS

EARTHQUAKE RISKS

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