Predictions

Scientists are constantly trying to learn new ways to predict the behavior of tsunamis. At this point, most data is gathered after a tsunami has already done its damage.

In a post-tsunami survey, a number of things are measured. Scientists are particularly interested in the inundation and run-up features after the waves strike land. Inundation is the maximum horizontal distance penetrated inland. Run-up is the maximum vertical distance above the sea level that the waves reached. Inundation and run-up are often determined by measuring the distance of killed vegetation, scattered debris along the land and eyewitness accounts of the incident.

Photo courtesy National Geophysical Data Center Tsunami generated by earthquake of April 1, 1946, Aleutian Islands, Alaska. On the left, a building before the tsunami. On the right, the same building after the tsunami.

Photo courtesy National Geophysical Data Center Damage from tsunami generated by earthquake of May 22, 1960, coast of Chile

Scientists have made great strides in monitoring and predicting the ongoing threat of tsunamis. One center continuously monitoring seismic events and changes in the tide level is the Pacific Tsunami Warning Center (PTWC). The PTWC is located in Ewa Beach, HI, and services the Hawaiian Islands and surrounding U.S. territories by working in conjunction with other regional centers. The West Coast & Alaska Tsunami Warning Center (ATWC) in Palmer, AK, serves the Aleutian Islands area along with British Columbia, Washington state, Oregon and California. This center is of particular importance because submarine earthquakes in this region have created waves that moved throughout the Pacific Ocean before striking elsewhere.

Tsunamis are detected by open-ocean buoys and coastal tide gauges, which report information to stations within the region. Tide stations measure minute changes in sea level, and seismograph stations record earthquake activity. A tsunami watch goes into effect if a center detects an earthquake at 7.5 or higher on the Richter scale. Civil defense agencies are then notified, and data from tidal gauge stations are closely monitored. If a threatening tsunami passes through and is noted by the gauge stations, a tsunami warning is issued to all potentially affected areas. Evacuation procedures in these areas are then implemented.

The Deep-Ocean Assessment and Reporting of Tsunamis (DART) uses unique pressure recorders that sit on the ocean bottom. These recorders are used to detect slight changes in the overlying water pressure. The DART system is capable of detecting a tsunami as small as a centimeter high above the sea level.

Photo courtesy NOAA DART recording device

The most serious problem facing humans is the fact that tsunami waves, once in motion, cannot be stopped. Scientists and civil agencies can only devote resources to predicting tsunamis and creating effective plans for protecting coastal areas from their ravages.

For more information on tsunamis and related topics, check out the links on the next page.