An earthquake generates a series of seismic waves that travel through the interior or near the surface of the Earth. There are four types of seismic waves.

How will three identically engineered buildings react to an earthquake on different types of substrate?

The first set of waves to be detected by seismographs are P waves, or primary waves, as they’re the fastest. They’re compressional or longitudinal waves that push and pull the ground in the direction the wave is traveling. They usually cause very little damage.

S waves, or secondary waves, come next since they travel more slowly than P waves. They travel in the same direction, but they shake the ground back and forth perpendicular to the direction the wave is traveling. S waves are more dangerous than P waves because they have greater amplitude and produce vertical and horizontal motion of the ground surface.

The slowest waves, surface waves, arrive last. They travel only along the surface of the Earth. There are two types of surface waves: Love and Rayleigh waves.

Love waves move back and forth horizontally.

Rayleigh waves cause both vertical and horizontal ground motion. These can be the most destructive waves as they roll along lifting and dropping the ground as they pass.

Want to learn more about earthquakes? Check out this video about how engineers use a giant shaking table to design earthquake safe structures.

How Seismic Waves Cause Damage During an Earthquake 3 January,2017Andrea Aust

  • Sadly lacking the science to prove that sediment doesn’t dampen the waves!

    • SmokeyJoeandthefish

      Soft sediment can dampen earthquake waves, but unfortunately it also tend to undergo liquefaction which can be even worse for a building than shaking.

Author

Andrea Aust

Andrea is the Senior Manager of Science Education for KQED, where she has been developing science education resources and providing professional learning for STEM educators for more than 10 years. Andrea graduated from UC Berkeley with a B.A. in Environmental Science and earned her M.A. in Teaching and Multiple Subject Teaching Credential from the University of San Francisco. Prior to KQED, she taught, developed, and managed marine science and environmental education programs in Aspen, Catalina Island and the Bay Area. Follow her on Twitter at @KQEDaust.

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