If a tsunami hits Kauai, go to higher ground.
A tsunami watch was issued for the state of Hawaii yesterday due to an 8.3 magnitude earthquake almost five miles underwater in the Pacific off the coast of Chile.
“In this case, an earthquake in Chile, it’s several hours before it’d reach Hawaii,” said Stephen Taylor, a professor at Kauai Community College who teaches geology and oceanography. “Earthquakes in Chile happen quite often and we’ve had several of those recorded in modern history.”
According to the National Weather Service, if a tsunami is going to impact Hawaii as a result of the quake, the first wave was projected to reach the beach this morning at 3:06 a.m.
According to the Mayor’s office, the best place to find evacuation information for tsunamis, as well as other natural disasters, is in the local phone book, at the front.
Tsunami evacuation zones on Kauai are the coastal areas all around the island and maps are available in the phone book.
“Often the first sign of an approaching tsunami is the ocean receding from beaches and harbors,” the phone book’s tsunami disaster guide says. “If you are at the shoreline and see this, move inland to higher ground immediately.”
People are advised to remain at least 100 feet away from inland waterways and marinas connected to the ocean. In the event of a warning, it might be a good idea to keep an eye on traffic and be prepared for a gridlock situation. That means if there’s too much traffic you might have to walk to higher ground.
If you’re not in an evacuation zone, don’t use your phone or travel anywhere unless it’s an emergency in order to keep communication lines and roads clear.
An issued watch means a tsunami reaching Kauai is possible, but it’s not necessarily going to happen. In the case of a watch, it’s a good idea to stay tuned in to local emergency management outlets, like the Kauai Civil Defense Agency, as well as the National Weather Service.
An advisory is the next level of tsunami information, meaning that strong currents are likely and people should definitely stay way from shore.
If a warning is issued, that’s when there’s an indication that it will happen, or that it is happening. Those same emergency management outlets will provide information on who should evacuate and where to go if there is a tsunami warning.
In the case of this tsunami, and others that are generated from places like Japan, the Hawaiian Islands usually have several hours of warning before impact, but locally generated tsunamis my only offer minutes of preparation time.
“It’s extremely unlikely, but the big island is a giant volcanic mountain and some of that land could settle,” Taylor said. “That could cause a tsunami and our warning time would be minutes, definitely less than an hour.”
A tsunami isn’t just one big wave, and that’s it. The phenomenon is actually a series of waves, called surges that travel outward from the epicenter of underwater earthquakes, or ones close to the ocean.
“These things are incredibly difficult to predict,” Taylor said. “Basically they have to wait for [this tsunami] to hit an array of buoys that are along the equator between Chile and Hawaii.”
That’s how tsunamis are tracked – by looking at satellite data reports from buoys in the open ocean that measure the change in water level.
“In the open ocean, the water level could go up just an inch, but when it moves into shallow water it slows down and the water piles up,” Taylor said.
So one inch of elevated waves out in the open ocean could become a wall of water once it reaches shore; predicting a tsunami isn’t an exact science.
“Considering the history of tsunamis, I would take a watch seriously,” Taylor said. “I wouldn’t be going down to the beach to check it out.”
According to the Mayor’s office, the last tsunami watch that was issued for Kauai was in August 2012. A warning was issued in October 2012, and an advisory was issued the following April.
“The 2011 earthquake in Japan caused a tsunami that did cause problems for Hawaii,” Taylor said. “I know the last couple of years, there were strong currents and it was a good thing that a watch was put on Kauai.”
Written for The Garden Island Newspaper, September 2015.