Japan’s ‘harbor wave’

The tsunami one year later


Japan tsunami - amplitude plot.

This image was created by NOAA's Center for Tsunami Research and graphically shows maximum wave heights (in centimeters or cm) of the tsunami generated by the Japan earthquake on March 11, 2011. It does NOT represent levels of radiation from the damaged Fukushima nuclear power plant. For more information please visit the original image and background information at http://nctr.pmel.noaa.gov/honshu20110311.

Download here (Credit: NOAA)

Imagine yourself out on a nice afternoon in your coastal town, picking up groceries for dinner, idling in rush hour traffic, or leisurely riding your bike along city streets with the beautiful Pacific Ocean in view.

Then imagine the terror you feel when the earth shakes violently and a voice comes across a loudspeaker urging, “Everyone near the shore, evacuate immediately!” This is what Japanese coastal residents experienced the afternoon of March 11, 2011, as tsunami warning sirens blared in communities along Japan’s eastern shoreline.

The 9.0-magnitude earthquake occurred less than an hour before tsunami waves roared ashore, and the world could only watch in horror as a heartbreaking disaster unfolded. The Japanese tsunami reached heights of up to 133 feet and inundated as much as six miles inland. It left in its wake nearly 16,000 dead; 6,000 injured; and more than 3,000 missing. Massive waves swept away homes, buildings, boats and vehicles in a matter of mere minutes.

NOAA tsunami buoy.

NOAA tsunami buoy.

Download here (Credit: NOAA)

NOAA predictions saved U.S. lives and property

Although the earthquake that triggered the tsunami originated across the Pacific Ocean, U.S.-based scientists at NOAA’s tsunami warning centers knew it would seriously impact parts of the nation’s West Coast. While this was a “near-shore” earthquake for Japan, the United States had the benefit of time to respond before waves began arriving.

Within seconds of the earthquake, NOAA scientists in Hawaii and Alaska were analyzing seismic information and running sophisticated models to determine the likelihood of a tsunami reaching the United Sates and nations in the Pacific Rim. NOAA’s early alerts and warnings enabled state partners to identify areas at risk, request people evacuate inundation zones, close roads, sound sirens, conduct door-to-door notifications, and implement the “reverse 9-1-1 system” — a call service that alerts the public of danger. Boats along the West Coast were moved out to open water to minimize costly damage and protect livelihoods.

NOAA scientists monitored the unfolding event for hours: They issued watches, advisories and warnings throughout the day, and predicted where and when tsunami waves might hit, and how high potential waves might be. Scientists used sea-level measurements received from NOAA’s DART stations and tide gauges to refine their predictions as the tsunami traveled eastward.

West Coast residents later confirmed that due to long-term public outreach efforts by NOAA and the states, they understood their risk of tsunami, were acutely aware of the warning in place and evacuated when told to do so.

Tsunami Hazard Zone sign.

Tsunami Hazard Zone sign.

Download here (Credit: NOAA)

Live and learn: How to survive a tsunami

Japan’s tragedy offers many lessons for surviving a tsunami either in along the coast of the United States or another prone region. Here are a few things to remember:

Tsunami debris on the move

To learn more about how NOAA scientists are using sophisticated models to track the movement of tsunami-related marine debris, visit this special resource page from NOAA’s National Ocean Service.

Posted March 14, 2012 NOAA logo.