November 10, 2005
Are you ready for a $30B quake?
By JACQUELINE MESZAROS
While most of us prefer not to dwell on it, Western Washington is part of the infamous Pacific Ring of Fire. Our concrete-and-steel structures are perched on a wrinkled crust spread over mobile plates of stone which, lubricated by lava, are converging in slow, shaky jerks, one over another.
As geologists like to remind us, earthquakes, volcanic explosions and tsunamis here are not a matter of if but a matter of when. We need to be smart about being ready, but how many of us know what it is we need to get ready for?
To help our region prepare for some of the hazards that face us, a team of scientists and emergency-preparedness professionals donated thousands of hours of their time to prepare a scenario study describing the likely effects of one of the major hazards we face: a magnitude 6.7 earthquake along the Seattle Fault Zone.
The study provides estimates of the human, physical and economic toll from such an earthquake, given the region's current state of preparedness. It is hoped that the report can help individuals, businesses and government anticipate what steps ought to be taken to ensure that our next natural disaster is not also a human catastrophe.
The Seattle Fault Zone, discovered just over a decade ago but studied in detail since its discovery, runs down Interstate 90, under Amazon.com, Safeco Field and across Elliott Bay. Geologists have determined that a quake on this fault about 1,000 years ago caused a 22-foot uplift of the floor of the bay, major landslides in the Olympic Mountains and a tsunami that raced across Puget Sound. But there were few inhabitants to disturb.
When the Seattle Fault slips next, much more than earth and water will be displaced. Buildings, bridges, roads and utility lines from Harbor Island to Lake Sammamish will experience shake similar to what Northridge experienced in 1994.
Using the same computer simulation program that the federal government relies upon to assess disaster impacts, the scenario team concluded that a large Seattle Fault earthquake will yield building collapses and falling debris that will kill more than 1,500 occupants and injure more than 20,000.
Nearly 10,000 buildings will be fully destroyed; nearly 30,000 more will be unsafe to occupy. More than 45,000 households will be displaced.
If the quake occurs during working hours, hundreds of thousands of commuters will have difficulty returning home because of damage to key transportation corridors. Families will be separated and communications will be overloaded, making it difficult to contact one another. While many residents will shortly find shelter with friends, co-workers or in hotels, more than 10,000 people will need the shelter of public facilities.
The scenario team expects that direct damage to buildings, inventories and infrastructure from a serious Seattle Fault quake will exceed $30 billion. These costs do not include secondary losses from business disruption or lost economic opportunities. In Kobe, Japan which is a city similarly configured to Seattle and likewise vulnerable to port, bridge and road outages indirect losses from its 1995 earthquake have been estimated to equal its direct losses. Kobe suffered $100 billion in direct losses and another $100 billion in indirect losses.
Roads highly affected
Transportation failures loom large in the scenario study, in part because so many major freeways cross through the fault zone and, in part, because transportation access will be so crucial to both immediate response and long-term recovery.
In the immediate aftermath of the quake, road failures will cut off important travel routes for emergency responders and create serious traffic jams that further inhibit emergency responders. In the longer run, road failures will slow repairs and recovery, making the region a far less pleasant place to live and work.
There is some good transportation news in that bridges built to modern code or fully retrofitted will sustain damage but will mostly not collapse. Still, we face serious vulnerability since the region's highest density of roads, overpasses and bridges are located directly in the fault zone. Unretrofitted transportation structures in the fault zone, like the Alaskan Way Viaduct, will collapse from shaking.
If ground displacements are very large, which is possible in this quake since they have been quite large in previous Seattle Fault quakes, even the new and retrofit bridges and overpasses in the fault zone are in danger. This is because, if land ruptures or liquefies and therefore moves large distances, support columns will also move significantly. Even retrofitted structures can't withstand the migration of basic supports.
It will take months if not years to restore failed bridges and overpasses. Consider, for example, that the viaduct carries 100,000 vehicles per day. As large volumes of traffic detour to surface streets, trips of a few miles could take hours. Commuting, supply, delivery and shopping patterns all will be inevitably altered.
It is hard to predict in advance which businesses will benefit from the disruptions and which will lose out. Some small firms will fail because of changes in transportation patterns. We also have to expect that the entire region will be less attractive to new businesses for some time to come.
While the scenario study describes only one possible event, it is meant to enable discussions of disaster preparedness in general. The chapter on Buildings and the chapter on Economic and Business Impacts both describe the effects of a quake in sufficient detail to help owners anticipate what preparations might make sense. The chapters on Lifelines, Essential Facilities and Response and Recovery, similarly, provide vivid detail about the kinds of challenges municipalities will want to prepare for.
The final chapter of the report provides recommendations for the entire state, including suggestions that we make it a priority to better prepare our critical public facilities, high-risk buildings and transportation infrastructure. These are the steps that the study team agreed would be valuable in helping ensure less disastrous effects and more likely recovery after our next large earthquake.
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