By Cornelia de Bruin

Triplicate staff writer

Suppose Crescent City Harbor's 5.9-foot slap from the ocean on Nov. 15 had been the size of the 21-foot tsunami that destroyed 29 city blocks in 1964 or larger?

Tsunamis have been documented at much larger sizes than the 1964 Good Friday series of waves that rolled across Crescent City. Sand deposits found in core sampling in and near Crescent City, and in Humboldt County, are evidence dating back as much as 2,500 years.

When a larger wave hits here, first responders will be busy securing damaged property, transporting the injured and recovering the dead.

Sheriff Dean Wilson and Crescent City Volunteer Fire Department have a list of the andquot;medically fragileandquot; members of the community. They will use that list to load up and transport them as quickly as they can.

Most of them likely will go to Sutter Coast Hospital. The medical facility is distant enough from low-lying areas that it isn't likely to be damaged.

Help from the outside would arrive by plane as a tsunami likely would flood parts of U.S. Hwy. 101 or cause landslides, making the road impassable.

But there's a limit to how much help could be provided via the airport. Improvements are needed to ensure that more than three large military cargo planes could land at the facility without damaging the runway, Wilson said.

Wilson strongly lobbied for improvements to Del Norte Airport in late October when U.S. Congressmen Mike Thom-pson, D-Calif. and Peter De-Fazio, D-Ore., were in town.

If the event triggering the next tsunami comes from the Cascadia Subduction zone the difference between it and what Crescent City and Del Norte County have witnessed recently will be huge.

The zone is the area south of Del Norte County and due west of Cape Mendocino where different floating plates of the earth's crust jockey with each other for position.

When it fractured in January 1700, as recorded in Japan, the waves that hit along beaches and lagoon areas in the two counties were big enough to leave nearly a foot of sand at the farthest back end of Lagoon Creek.

Core sampling from there documents that deposit and numerous others.

andquot;The paleotsunami deposits at Lagoon Creek are at the back of the lagoon,andquot; said Lori Dengler, chairwoman of Humboldt State University's Geology department. andquot;We have found seven of them.andquot;

Because of its nearness, a Cascadia-generated quake would send waves to Crescent City's beaches and farther within five to 10 minutes.

If it were strong enough, it could collapse or damage the Collier Tunnel that brings U.S. Hwy. 199 from Oregon into Del Norte County.

Officials haven't estimated how many bridges would be damaged or landslides triggered to render U.S. Hwy. 101 and state Hwy. 197 out of commission.

Essentially the population here would be on its own until help came by air or sea.

We would count on our local responders to render aid to those most severely hurt and local Ham radio operators to help them get the word out to the larger world.

As those surviving Hurricane katrina's devastating strike on New Orleans and the Gulf Coast, it's best to presume we'll be on our own for a while should a tsunami strike.

andquot;If you live in the run-up zone, have a bag that has a flashlight in it packed and ready to go,andquot; said Troy Nicolini. andquot;If you live on higher ground, be prepared to survive the earthquake and meet your needs for 72 hours to one week.andquot;

Nicolini works for the National Weather Service Eureka office and heads Redwood Coast Tsunami Work Group.

The run-up zone presently sketched on maps of Crescent City may change during the next year. That's because it shows where a Cascadia generated wave would wash.

Waves from farther away would not inundate as much of an area. Dengler said the change, if it's made, would help prevent highways from being clogged with the unnecessary traffic of people who don't need to evacuate.


'Medically fragile' list

If you've recently moved here and should a tsunami strike think you might need help - for example, you can't drive, run or hike a great distance - contact the Del Norte Health Department at 464-3191 to inquire about being added to the andquot;medically fragile.andquot;