We can prepare for earthquakes, but we can't predict them

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In the last six weeks, Hawai`i residents have been shaken by two major earthquakes and numerous aftershocks.

We can prepare for earthquakes, but we can't predict them...

Note: HVO normally emails our weekly column, called Volcano Watch, on Thursdays and the Hawai`i Tribune-Herald publishes them in their Sunday edition. Because of the continuing aftershocks from the October 15 quakes and the false rumor being passed around regarding earthquake predictions, HVO scientists feel the need to share more information than usual. Last week's Volcano Watch dealt with aftershocks and what to expect and this one discusses earthquake prediction. We will resume our normal weekly schedule this Thursday.

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Then, on the last Sunday in November, they were subjected to a new danger: Rumors predicting that a magnitude-9 earthquake and tsunami would strike sometime that night rocked the state of Hawai`i. With their memories of the two damaging earthquakes on October 15 still fresh, residents were understandably concerned and even fearful.

People stocked up on gasoline, provisions, and emergency supplies, and gathered to compare notes about what they had heard. Some evacuated from areas they perceived as dangerous. Police, television, and radio stations were flooded with telephone calls for confirmation of the rumors. NOAA's Pacific Tsunami Warning Center was also hit hard with incoming calls requesting information.

Accurate and reliable information was absolutely critical. The fast-spreading rumors were potentially harmful, and public officials and broadcast media quickly responded to dispel them. The official messages were clear and concise: It is not scientifically possible, at present, to predict earthquakes. There was no official earthquake or tsunami prediction. And, certainly, no government entities were withholding information about a prediction that didn't exist.

The United States Geological Survey (USGS) is the federal agency responsible by law for routine monitoring of, and providing notifications relating to, earthquakes, volcanoes, and landslides. Where appropriate, the notifications include warnings and forecasts. The Hawaiian Volcano Observatory is the office of the USGS whose duties include earthquake and volcano monitoring in Hawai`i.

Much research has been done by the USGS and university scientists to understand earthquakes. Besides improving our understanding of earthquakes, this research might eventually result in the ability to predict them, but so far that goal has not been reached. So-called alternate (non-scientific) methods of earthquake prediction have also been tested and found to be unreliable, despite proponent's claims.

To be testable, a prediction should include a statement of the future earthquake's specific location, magnitude, and time of occurrence. A prediction should also include the methodology or basis for prediction, to allow independent testing and verification. Sunday's rumor-borne prediction was difficult to test but was unfulfilled.

To keep abreast of new approaches and applications for earthquake prediction, the USGS has recently reestablished a National Earthquake Prediction Evaluation Council. The Council is made up of a number of USGS and university scientists and provides objective and expert analysis and opinions on earthquake prediction. The Council reviews predictions and resolves scientific issues relating to earthquake prediction.

Even if we can't predict the time and place of future earthquakes, we can reduce the damage they inflict through strong ground shaking by recognizing the areas where damaging earthquakes occur most frequently. The USGS publishes seismic hazard maps for the entire United States. Based on earthquake statistics, geology, and knowledge of the way earthquake energy spreads, the national seismic hazards maps show areas of likely strong, earthquake-generated ground shaking. As we learn more about earthquakes, the maps are updated.

Seismic hazards are expressed in terms of probabilities that specific levels of strong ground shaking will be exceeded in a 50-year interval. The USGS National Seismic Hazards maps for Hawai`i Island show that it is one of the highest hazard areas in the US. These maps are used to develop modern building codes. Thus, even without the ability to predict earthquakes, safer buildings and structures in earthquake-prone regions will hopefully save lives and reduce losses due to earthquakes.

Scientists have also calculated earthquake probabilities for specific regions, using new geological and geophysical data, theories, and modeling techniques. Quite noteworthy is the work done for the San Francisco Bay Area which has determined that there is a 62% chance that a magnitude 6.7 earthquake will strike there before the year 2032.

Large earthquakes are certain to strike Hawai`i, and we should not be completely caught off guard by earthquakes like last month's. In fact, work published in 1992, determined that there was a 75% chance that a magnitude 6.5 or greater earthquake would strike the Hawaiian Archipelago before the year 2010. The magnitude-6.7 Kiholo Bay earthquake on October 15, 2006 proved the validity of this approach.

It is very important for government, business, and the general public to use earthquake probabilities and seismic hazards maps, as well as other information available about earthquakes, to plan for future damaging quakes. It is equally important to improve earthquake monitoring and to continue to pursue basic earthquake research to improve our ability to understand and live more safely with earthquakes. skip past bottom navigational bar.


Volcano Activity Update

An update is not included with this Volcano Watch article.