Tsunamis have been a reality for coastal communities for as long as humans have lived near the shore. NOAA Sea Grant has been working with coastal communities for many years to help residents understand the risks, reduce their vulnerability and respond quickly. Hazard resilient coastal communities is one of four major areas of focus for the National Sea Grant College Program. Sea Grant uses its integrated research, training and technical assistance capabilities to help local citizens, decision makers and industries plan for these hazardous events around the U.S. and its territories.
When the 9.0 m Tōhuku earthquake hit on March 11, 2011, it generated a tsunami with 10 meter (30 foot) waves that crashed on the shore of Japan less than a half an hour after the quake. Soon, the waves were racing across the ocean towards Hawaii and the West Coast of the United States.
The tsunami surged into the Hawaiian Islands around 3:45 a.m. local time, about seven hours after striking Japan. The 2 to 4 m (6-12 ft) waves caused millions of dollars in damage to buildings; yet, there were no human casualties. Most residents in the islands were prepared and areas prone to inundation were evacuated. University of Hawaii Sea Grant has supported cutting-edge tsunami research, including an improved prediction model and maps for tsunami run-up and coastal inundation from researcher Kwok Fai Cheung. Inundation maps help island and emergency managers know which areas are at risk during tsunamis. Cheung’s model, which takes water level data near the tsunami source and provides an accurate estimation of the tsunami size, providing a clearer picture of potential damage, has been implemented for tsunami inundation mapping in Hawaii, the US Gulf Coast states, Puerto Rico, Chile, American Samoa and adapted by NOAA’s Pacific Marine Environmental Laboratory into a tsunami forecasting tool.
The tsunami hit the coast of Oregon a half an hour later than expected, arriving at 7:48 a.m. local time. In most areas the small waves were more like the tide rather than a tsunami. Alarms had been sounded and several coastal areas were evacuated. Oregon Sea Grant takes tsunami preparedness very seriously. The coast of Oregon is on the Cascadia subduction zone – a 600 mile long fault line similar to the one near Japan. Pat Corcoran, the Oregon Sea Grant Coastal Hazard Specialist, has developed workshops, videos and guides on tsunami preparedness. Corcoran says that there are three things everyone near a coast should know about tsunamis. First, there are two kinds of tsunamis – local and distant.
“If you feel an earthquake, it’s a local event,” says Corcoran. “Large earthquakes cause large tsunamis. If you’re at or above 50 feet elevation, stay there. If not, run for the highest spot you can get to within 15 minutes. “
He goes on to explain that if you hear a siren, then you should get more information – it is probably a distant event and you may have hours before you need to evacuate. As part of his work, Corcoran has created messages tailored to his audiences (for example, fishermen, realtors and homeowners). He is also working with local businesses to train their staff how to respond in the event of a tsunami, for both personal safety and the safety of their customers.
Oregon Sea Grant has led the way in developing recognizable tsunami evacuation signage. The signs also have been adopted in Washington, California, Alaska and Hawaii. Now, the warning signs are going global. After the Indian Ocean tsunami in 2004, the Oregon Sea Grant design was posted on new warning signs along Thai beaches as part of Thailand’s new National Disaster Warning Centre.
The Pacific Coast of the United States is not alone in its vulnerabilities to tsunamis. Just north of the islands of Puerto Rico, lies the Puerto Rico trench with its large subduction zone, which creates a very real tsunami threat for Puerto Rico and the U.S. Virgin Islands. Puerto Rico Sea Grant actively participates in the development of a Caribbean tsunami warning system similar to the one in the Pacific Region. Their work also sheds light on public perceptions of risks and the economic impacts of coastal hazards.
While Sea Grant has been active in tsunami research and preparedness for some time, there is still more work that needs to be done. According to Corcoran, “For us to think we are going to get what Japan got is pretty sobering and I don’t think people want to deal with that. The implications are fairly unimaginable.”