Earthquakes release waves of energy called seismic waves. They travel through the interior and near the surface of the Earth.

P-waves, or primary waves, are the fastest moving type of wave and the first detected by seismographs. They are also called compressional or longitudinal waves, and push and pull the ground in the direction the wave is traveling. They usually cause very little damage.

S-waves, or secondary waves travel more slowly than P waves. These waves 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, causing the ground to rise and fall as they pass.

seismicwaves-web_copyright 2012


This post is part of Exploring Earthquakes, a rich collection of resources co-presented by the California Academy of Sciences and KQED. This material is also available as a free iBooks textbook and iTunes U course.

Don’t miss Earthquake, an interactive exhibit at the Academy exploring the seismic forces that impact us today and featuring the Shake House, an earthquake simulator.

What Are Seismic Waves? 14 April,2016Andrea Aust

Author

Andrea Aust

Andrea is the Senior Manager of Science Education for KQED. In addition to QUEST, she’s had the pleasure of coordinating education and outreach for the public television series Jean-Michel Cousteau: Ocean Adventures and the four-hour documentary Saving the Bay. 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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Jenny Oh

Jenny is a long-time contributor to Bay Area Bites, KQED’s popular food blog. She formerly worked as an Interactive Producer for the Science & Environment unit. Jenny graduated with honors from New York University’s Tisch School of the Arts Film and Television program and has worked for WNET/PBS, The Learning Channel, Sundance Channel, HBO and the University of California.

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