Potential Bellingham Bay Earthquake Damage

Recent death and destruction by a tsunami on the edges of the Indian Ocean reminds us that there is a serious potential for damage in the Bellingham Bay area, including the land about to be rebuilt.

I am a retired geologist, so I was also reminded that I was a member of a committee at Western Washington University that studied the potential for damage by an earthquake at the university and what could be done about it. I chose to study geological aspects, so I thoroughly studied tsunamis and wrote a paper that was published in 2002 by Whatcom Watch. Much of it is as fresh today as it was then.

A number of geologists and geophysicists believe the greatest danger to structures in Bellingham Bay and the waterfront could be from a tsunami, a huge wave 30 or even 60 feet high, generated by a submarine earthquake. However, expert testimony at a meeting on March 21, 2002, conceded that danger from a tsunami had not been considered. In a sense, that is not surprising.

Peter May, et al of the University of Washington in 1989 published “Anticipating Earthquakes.” His group rated the political prospect of reducing the risk of earthquake damage in 13 cities from Bellingham to Portland and placed them in groups. Bellingham was placed in the group of most risk due to lack of preparedness. I see no evidence that anything has changed.

The unstable earth’s crust has been likened to the skin of an orange. Remove part of the skin of an orange, replace it and then slide the piece to one side. That will slide the piece over the skin still in place on one side, and leave a depressed gap on the other side. The North American and South American plates are sliding relatively westward at about the rate fingernails grow. The Atlantic Ocean is widening on the east. To the west, the North American continent is sliding over the Pacific Plate and forming mountains, creating volcanoes and causing earthquakes. That’s the big picture. Our coast has not had a great earthquake on the order of 8.0 on the Richter scale in the last 300 years while coasts of the rest of American continents remain seismically active. Can our own coast remain quiet? That is the big question.

The term tsunami is of Japanese origin and began to be introduced to American English about the middle of the 20th century after the distinction between wind-generated waves and those caused by submarine earthquakes became better understood. Tsunamis steepen and increase in height as they enter shallow water. Waves on the order of 30 feet high are common; waves 60 feet high have been recorded.

In detail, smaller pieces of the Pacific plate dive under the North American continent from California to Vancouver Island. The piece diving under us is called the Juan de Fuca plate, and the zone where it dives is called a subduction zone. The edge of the North American plate where the Juan de Fuca plate begins to dive is offshore. Hence, when there is movement between the two plates, a submarine earthquake results. Geological evidence indicates that the plates remain stuck together for a time, and then move generating a great submarine earthquake and a tsunami.

David Engebretson, professor of geology at Western Washington, warned in a Bellingham Herald article on Nov. 7, 1989, that, “It is almost certain that a great earthquake—on the magnitude of 8.0 or more—will occur in this region.” He added that, “Great earthquakes occurred in this region 300, 1000, 1600, 1700, 3100 and 3400 years ago . . . As it has been 300 years since the last earthquake, we are due another anytime.” Science News on Feb. 27, 1990, said that Brian Atwater, of the U.S. Geological Survey, had found evidence of several tsunamis in coastal sediments of this region.

No, I don’t mean politics; that already is fluid. I refer to earthquakes causing fill, and soft, unconsolidated sediments, to shake like Jell-O in a bowl. That is called liquefaction. A great deal of the waterfront is built on fill; moreover, most or all of the waterfront at depth rests on soft sediments largely deposited by the Nooksack River. The evidence of liquefaction is not new. I studied it many years ago while in college. It is often ignored by builders and promoters.

Liquefaction or a tsunami both depend upon where a large earthquake is located. One offshore in deep water produces a tsunami. One in the vicinity of soft, wet sediment or land produces liquefaction. Here is another quotation from Peter May, et al. “Perhaps the greatest source of seismic vulnerability for ports results from the fact that port facilities in this region tend to be built on alluvial plains and extensive fill areas.” And you will recall that Peter May, et al, placed Bellingham in the category of the most politically vulnerable to earthquake damage. Bellingham, you have experts right next door at the university. Why not use them?

Public input is best achieved through an environmental impact statement (EIS). Following are the steps in an EIS. Early in the process, there is a “scoping” meeting where public input is invited. Then the government is required to respond to questions, and again citizens are allowed to respond to the draft EIS.

Certainly an EIS should be required regarding the seismic hazards. I think the Bellingham City Council would be wise to hold early scoping meetings on plans to redevelop the waterfront even where the law does not require such a meeting. The purpose of this EIS would be to ensure that reasonable steps are taken in reconstruction the Bellingham waterfront to save lives and property. §