A tsunami is a collection of several giant waves typically in the ocean that are most often formed by earthquakes. As we know from the recent tsunamis caused by the devastating magnitude 9.0 earthquake in Japan in 2011 and the deadly 9.1 earthquake in Indonesia in 2004, they are as much a danger as the earthquake itself if not more dangerous.
Earthquake induced tsunamis are caused by when the tectonic plates move against each other on the ocean floor. This large abrupt motion causes the water above to move and the transfer of energy from solid earth to the ocean is made.
On April 1, 1946 there was a magnitude 7.4 earthquake off the coast of Alaska that triggered a tsunami that killed 159 people in Hawaii. A massive wave estimated at nearly 100 feet high devastated Unimak Island, AK as the 500 mile per hour wave was heading toward the southern Pacific.
About 5 hours after the earthquake, a 32-foot wave destroyed almost a third of the town of Hilo Bay, Hawaii (2,400 miles south of the quake’s epicenter). Unfortunately the tsunami wasn’t done. Waves reached as high as 60 feet on other parts of Hawaii destroying everything in it’s path as there was no warning system at the time. This shocking event prompted the U.S. to establish the Seismic SeaWave Warning System (now called the Pacific Tsunami Warning System) two years later.
Since then, technology has been advancing so much over the last 20 years that we’re able to detect whether there is a tsunami threat within minutes after an earthquake hits. The DART (Deep Ocean Assessment and Reporting of Tsunamis) II System consists of two main parts. A seafloor BPR (bottom pressure recording) package which detects pressure changes caused by the tsunami and a surface buoy which receives this information and transmits the data to a satellite. The data then is immediately transmitted from the satellite to ground stations for analysis.
Isn’t technology amazing? If you live in a coastal area where there is a tsunami threat, please be prepared. Remember the following when a tsunami hits.
- DON’T go near the shore to watch the tsunami. Chances are, if you can see it then you are too close to escape.
- DO go to higher ground. The further away from shore and the higher you are the safer.
- Tsunamis occur in multiple waves so even if you are safe after the first wave, stay put until authorities declare it is safe.
- Flooding usually occurs after a tsunami. It can be dangerous walking or driving through a flooded area as you never know what’s inside as the water is pretty murky. Sharp debris can cause you harm or you might get yourself tangled.
I’ll be writing an article on tsunami preparedness and what to do before, during, and after just like what I did for earthquake preparedness in the next few days.