SMALL TEMBLOR A REMINDER: CRESCENT CITY A PRIME SPOT FOR RAGING TSUNAMI WAVES

January 17, 2001 11:00 pm

By Kent Gray

Triplicate staff writer

Many scientists have called Crescent City the capital of tsunamis.

So it is not surprising that when people felt Saturdays 5.0 earthquake, originating off the coast of Eureka , it caused some concern.

As the anniversary of the 1964 tsunami approaches, the Del Norte County Office Of Emergency Services Steve Crockett believes it is time for Crescent City residents to reacquaint themselves to the dangers of such a disaster.

If another earthquake happened in Alaska, the warning time would be quite long, says Crockett. The city police, in conjunction with the Sheriffs Department, would have time to evacuate the downtown area.

A more problematic question arises when dealing with a local earthquake, where warning times can be as short as 10 minutes.

This is where we have to set up some educational guidelines on what to do and where to go, says Crockett.

The tsunami warning siren, located in the harbor area, is not automated so 10 minutes may not allow enough time for a staffer to set it off - especially at night.

Ron Sandler, Crocketts predecessor, said Someone could go ahead and hit the button on the way out, but they shouldnt risk their life to do it.

A local earthquake strong enough to create a tsunami would probably knock out power to the siren anyway, according to Sandler.

The fault off Del Nortes coast, called the Cascadia subduction zone, is capable of producing earthquakes of 8.5 or greater; large enough to knock people off their feet.

This is when people need to be aware of a possible tsunami, according to Lori Dengler, director of the Humboldt Earthquake Education Center.

If you feel the ground shaking - very strongly - for 30 seconds or longer, its a good indication of whether or not you are dealing with an earthquake large enough to produce a significant tsunami, said Dengler.

Dengler, who is also a geology professor at Humboldt State University, said people should also be aware that most earthquakes do not pose a tsunami risk.

In most cases you are probably putting yourself at more risk by evacuating rather than by staying put, said Dengler. The overwhelming majority of our earthquakes are not going to produce a tsunami, so it is safer to remain in your house.

Estimating the size and length of an earthquake is one identifier of a possible tsunami. Another is location.

Its useful both to understand what areas are at risk and then what are the real warning signs - then you can skedaddle as quickly as possible, said Dengler.

The areas at risk of a tsunami are dependent on several factors: elevation, distance from shore, any obstructions the water must overcome and even tide levels.

There is agreement that two miles from the shore is the beginning of the safe zone; In Crescent City, that translates as 9th Street.

The 1964 tsunami, which consisted of four waves spanning a three-hour period, covered some areas of 5th Street. Dengler says a stronger tsunami is not only possible but likely along Crescent Citys coastline.

The Cascadia subduction zone may be responsible for the powerful tsunamis which appear to ravage the coastline about every 300 years.

The Crescent City area is where we have some of the best evidence anywhere along the west coast where some of these very large local tsunamis have occurred, said Dengler.

In contrast, the 1964 tsunami deposited a half-inch of sand. The deposit from the year 1700 is about five inches thick.

According to the evidence, Crescent City is overdue.

The International Tsunami Society is scheduled to meet in Seattle in early August. Dengler plans to bring some of the scientists to Crescent City at that time.

Closer to home, the California Tsunami Steering Committee will be meeting on March 5 and 6 in Oakland.

Steve Crockett said the results should benefit Del Nortes disaster preparedness.

The community needs to be educated and a scenario needs to be put in place and practiced, he said.