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Pacific Coastal & Marine Science Center

Tsunamis & Earthquakes

USGS PCMSC Tsunami and Earthquake Studies

 

Persistence of Tsunami Waves

Do tsunamis stop after they first strike land? No!

Part of the tsunami energy is reflected back to the open ocean and scattered by sharp variations in the coastline. In addition, a tsunami can generate a particular type of coastal trapped wave called edge waves that travel back-and forth, parallel to shore. These effects result in many arrivals of the tsunami at a particular point on the coast rather than a single wave.

Because of the complicated behavior of tsunami waves near the coast, the first amplitude and surge of a tsunami is often not the largest, emphasizing the importance of not returning to a beach many hours after a tsunami hits.

Northern California

To illustrate this phenomena, the simulations below show tsunami wave behavior along the northern California coastline. For visualization purposes, tsunami wave amplitudes are exaggerated and 2.5 hours of elapse time has been compressed into 30 seconds of animation time.

View to the south-east. Download .mov file 3.5 MB
(Mac: click and hold mouse button; Windows: right-click)

View to the north-east. Download .mov file 2.1 MB
(Mac: click and hold mouse button; Windows: right-click)

Central California

The simulations below show tsunami wave behavior long the central California coastline. For visualization purposes, tsunami wave amplitudes are exaggerated and 70 minutes of elapse time has been compressed into 20 seconds of animation time.

View to the south-east. Download .mov file 3.6 MB
(Mac: click and hold mouse button; Windows: right-click)

View to the north-east. Download .mov file 2.0 MB
(Mac: click and hold mouse button; Windows: right-click)

Resonance within harbors and estuaries is not shown in these simulations, but it is another important aspect that contributes to the persistence of tsunami waves.

 

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Page Last Modified: 2 September 2008 (lzt)