Large waves

February 27, 2010 Tsunami

This tsunami was generated in Chile, from a M 8.8 earthquake. We send our deepest condolences to our friends, families, and colleagues in Chile at this time of devastation.

Gen photo

The waves that struck Hawaii were impressive, but fortunately, not damaging. Photos above were taken by Genevieve Cain, who recorded a series of draining and filling of the Bay, at Hilo Lighthouse. Left, a typical withdrawal at 11:30 am; right, a large surge at 12:52.

The public enjoyed views from a safe distance under sunny skies. In Hilo, considered by many to be the Tsunami Capital of the World, a fascinating situation occurred. After the tsunami waves died down (they were strongest from 11:00 am - 2:00 pm), the seiche wave set up within the breakwall of Hilo Bay continued for hours. Water sloshed back and forth at regular intervals, running up rivers and first covering, then exposing, rocks at shorelines. The particular shape and size of Hilo Bay is ideal for creating seiche waves. You can create seiche waves in your own bathtub: notice how, if you slosh water to one end of the tub, it continues to race back and forth for a long time. Hilo Bay is like a giant bathtub, and that is why it's especially important to stay far inland for tsunamis in Hilo; tsunami waves can unpredictably grow to dangerous proportions as a result.

 

Foster graph

The graph above shows data collected by Dr. James Foster of UH-Manoa, from the brand new Keokea Tide Gauge on Oahu. "The waves arrived a little later than predicted and were, thankfully, even smaller. You can see that the biggest one measured about 1 foot from trough to peak here in the marina--enough to stir up the water and get some currents going, but non-threatening, just the way we like them. Things were still churning a little even 6 hours later."