Like everyone else, we have been saddened and horrified by the tremendous loss of life and the suffering in Turkey and Syria caused by the twin powerful earthquakes and their aftershocks. Tens of thousands of buildings collapsed, trapping and killing so many people as they slept. More than 100,000 buildings that didn’t collapse were damaged so extensively that they must be demolished, leaving more than 1 million persons without homes.
This disaster struck a faraway region, and you may think, “Surely we are much better off, and it couldn’t really happen here.” But the Puget Sound region has similar faults and an abundance of buildings designed and built before our current understanding of the region’s seismicity and modern structural engineering practice. We cannot be complacent in the face of the very real risk of an urban earthquake.
In Turkey, the magnitude 7.8 first quake came without warning, followed only hours later by a second quake that was nearly as strong (magnitude 7.6). The destruction was so extensive because of two factors: First, the faults that slipped are about 200 miles long, lie near the surface, and run right through or near to urban areas which were shaken very hard — the worst shaking is often closest to the fault. Second, while Turkey has strong building codes similar to ours here in Seattle, many older buildings had not been strengthened to modern standards, and apparently some newer buildings were not constructed properly, in violation of those codes.
Here at home, we’ve all heard of the potential for the “Big One” — a giant earthquake from the mostly undersea fault off the Pacific Coast. But our faults that most closely resemble the ones in Turkey are closer in: the Seattle Fault and its close neighbors, the Tacoma Fault and the Southern Whidbey Island Fault.
Each of these faults is believed by the United States Geological Survey and University of Washington scientists to be capable of a magnitude 7 or greater earthquake, potentially producing shaking vastly stronger than we experienced in the 2001 Nisqually Quake. We don’t know what the upper limit on that magnitude is, but it could quite plausibly be 7.5 or even more. Millions of people and tens of thousands of buildings, thousands of bridges, key port facilities and even Navy nuclear submarine bases are at risk of extremely violent shaking from these three faults — and perhaps from others we haven’t yet identified.
The Seattle Fault runs from west of Bainbridge Island right through Sodo, the Port of Seattle, Mercer Island, under Lake Washington and the Eastside. The Southern Whidbey Island fault extends across that island close to Everett, but may extend from Vancouver Island all the way to the Ellensburg-Yakima region. The Tacoma Fault lies just north of downtown and the Port of Tacoma. Each of these faults has clear evidence of past earthquakes; for the Seattle fault they’ve even been dated to about 1,100 years ago and possibly again 200 years ago.
Our faults are much more similar to the ones in Turkey than you might think. The Southern Whidbey Island and Seattle faults could even link up to produce not one but two major quakes in quick succession, like the ones of Feb. 6 in Turkey.
Our building stock is probably better off than that in southern Turkey but is far from earthquake safe.
In recent decades, Washington state has greatly improved seismic safety through improved building codes, and a wealth of global experience and engineering research gives us confidence that this has made a real difference. However, thousands of older buildings have not been brought up to the same standard and our understanding of the seismic hazard in the region has evolved rapidly in the last decade alone.
There are known to be more than a thousand unreinforced masonry buildings (URMs) made of brick or stone and mortar without any steel reinforcing as is required today in the city of Seattle alone, with many more in cities and towns throughout Western Washington. These URMs present a real risk of partial or complete collapse in the face of seismic shaking and are a cause of loss of life in earthquakes around the world.
There are certainly even more of what are called non-ductile concrete buildings and bridges, constructed before about 1980, which have inadequate steel reinforcement and are at risk of the kind of horrific collapses we have seen in the recent news from Turkey. We don’t even have a good count of how many of these there are in our cities and towns in the Pacific Northwest, but because they tend to be larger buildings they put larger populations at risk. Notably, Los Angeles County just initiated a process to understand the scope of the non-ductile concrete building problem there; we need to do the same.
There are also many buildings designed with open ground floors for retail space or parking, the so-called “soft story” that is vulnerable to collapse. In older buildings that level is often weak and prone to collapse in earthquakes. Finally, while wood frame houses tend to have thankfully smaller casualty rates from collapse because they are lighter and more flexible, they are prone to major structural damage if not retrofitted, a major potential source of societal disruption and economic loss in an earthquake.
The bottom line is that it is unfortunately entirely realistic that a major earthquake here in the Puget Sound region could cause thousands of deaths and injuries and many billions of dollars in loss of property. It would take many years to recover from.
So what can we do? We don’t know when the next major quake will be. But while one could strike at literally any time, it is also more likely that it will be decades from now. We should use that time to prepare wisely, to avert the worst of a massive disaster like what Turkey and Syria have gone through.
∙ Get serious about identifying and retrofitting older buildings, bridges and other infrastructure. We are way behind California, Oregon and British Columbia on this effort. It will cost money, but lives are at stake. Much of the population in Turkey is justifiably demanding to know why their elected leaders didn’t do more to prepare before the disaster. The state Legislature should build on recent steps like the small but meaningful passage of the seismic safety in schools program last year with something far more comprehensive. Such an effort will need to include ways to incentivize private owners to improve older buildings.
∙ Build for resilience, not simply for survival. Current building codes aim to protect occupant lives in a building but not to prevent irreparable damage short of actual collapse, rendering our buildings useless in the aftermath. Some newly built hospitals in Turkey were constructed with available technology that isolates the building from its foundation on bearings, essentially allowing the ground to move under the building without transferring large forces. Those hospitals came through relatively unscathed. Seattle has only a handful of buildings with this base isolation, while San Francisco and Los Angeles have more but still many less per capita than in countries like Japan, Chile and New Zealand. The additional costs for employing base isolation for a new structure are modest (5% to 10% of construction costs).
In short — it could happen here. We know what to do and just have to find the will to do it. Our lives literally depend on it.
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