What the first five minutes of the biggest quake ever to hit the continental US will feel like to those on the ground. Part 1 of 5.
On a Thursday in April, at 11:44 AM, there is a major Cascadia Subduction Zone earthquake, epicentered fifty miles off the coast of Newport, Oregon. The quake has a magnitude of 9.0 Mw—it's felt as far south as Northern California, and as far north as British Columbia. In the Portland Metro area, this is felt as a "Strong" VI intensity quake, on the Modified Mercalli Intensity scale. Scientists believe there is up to a 15 percent chance such an event will occur in the next 50 years.
This is the first in a 5-part piece of reported science fiction about what will happen next when it does.
The ground begins to move at 11:44 AM on a Thursday in April. Trees sway and the buildings that comprise Portland's low-lying skyline begin to rumble and shake. People begin reaching for their cell phones. They wait, apprehensively, for the shaking to stop—or to increase. They wait for the earth to open up and swallow cars like it does in the movies. It never happens. The rumbling just continues, businesslike, a new normal of lateral acceleration forces.
Cacophony swells from the city as if it is howling in response to the earth's call: car alarms, shattering glass, the thudding of bricks popping out of building facades, humans screaming in fright, and far off, echoes of what sound like dumpsters clattering to the ground from the jaws of garbage trucks. It is the sound of shifting foundations and collapsing masonry, continuously, a roar increasing from every direction. It is the sound of the living surfaces that a city takes for granted becoming undone.
The shaking is not that strong, but the length of the quake slowly but surely shakes the life out of many of the city's structures.1 There are many partial collapses, and houses that have slid off their foundations.2 Unreinforced masonry buildings built before any seismic codes are the most vulnerable, because their bricks are simply shaken apart from each other until the walls no longer exist. These fashionable, retro-looking warehouses and apartment buildings along the waterfront and older arterial streets are now largely piles of rubble.3
Newer buildings—those constructed after 1994 in Portland were built to higher seismic standards—suffer mostly superficial damage, or at least maintain enough of their structures to prevent collapse, and avoid any serious, immediate injury to the inhabitants.4 Wood frame construction is also not too badly off, as the wood can absorb more rebounding spectral acceleration force5—though only so much and for so long.
The shaking occurs across the city in a fairly uniform fashion. In more localized quakes, geology creates local variations in shaking intensity. Contrarily, the CSZ quake is huge, and yet relatively distant from the city. Portland's shaking is generally equivalent in all areas, though with slightly stronger shaking in the west, and close to the Willamette river.6
But to fully understand what is now happening to Portland, you have to understand its geography.
Portland has two rivers, which are now gently rippling and churning: the only clue of the infrastructural calamity occurring below the surface. The Willamette splits the city nearly in half along a mostly north-south axis before meeting the Columbia—the largest river flowing into the Pacific Ocean in North America—which is both the city and the state of Oregon's northern border.
A single massive landslide is responsible for the vast majority of immediate deaths.
Portland's rivers both have important deep draft shipping channels dredged into them: the Willamette River has shipyards, as well as cargo terminals all the way into downtown. These dredged channels collapse in the earthquake quite quickly, as the shaking causes underwater landslides that send mud and sand into the deep center channels, making ship traffic difficult or impossible in the coming weeks.7 These underwater landslides will go unnoticed by most, especially compared to the landslides above the water.
The city of Portland is generally divided into five quadrants: The Northwest and the Sourthwest (west of the Willamette River) and the North, Northeast, and Southeast (on the east side). Downtown is located where the Northwest and the Southwest meet, along the Willamette.
Portland is a rainy, river city without a recent history of seismic activity. This geology will prove fatal in many areas. The first and most catastrophic vulnerability is the susceptibility of landslides in the loose soils and heavy trees on its hills and bluffs.8
At 11:46AM, two minutes into the earthquake, the soil on the steep eastern slope of the West Hills, wet and heavy after a recent week of spring rain, comes loose and flows downhill. What was once solid ground becomes liquid, creating a wave of mud and debris, folding buildings over like dominos between West Burnside and SW Jefferson. Nearly everything west of W. 18th Avenue is destroyed as the city right off the mountainside. This single massive landslide is responsible for the vast majority of immediate deaths.
Many people will never be found, as thousands of tons of earth displaces itself as if the the city blocks were flipped by a plow. Smaller landslides are burying roads and rail lines elsewhere, all across Oregon. The single tunnel that allows the majority of road traffic to cut over the West Hills to the the suburbs of Beaverton, Tigard, and Hillsboro is buried at its eastern entrance, due to landslides above it dropping soil onto the roadway of Highway 26.9
On this late morning in Multnomah County, the central county of the Portland Metro Area, 154 people die instantly from the collapsing buildings, landslides, and resulting traffic accidents. 2,463 are injured.10
Liquefaction is a killer as well, hiding within Portland's riverine geology, set loose by the shaking of the earth.11 The earthquake shook Portland's river soils like coffee grounds floating in a French press. Ground that was previously solid turns to quicksand. Raised areas of ground spread downhill like pancake batter, cracking pavement, pushing over retaining walls, swallowing heavy objects like cars or building foundations, and floating buried objects like utility lines to the surface, or snapping them in place.
Liquefaction causes the Harbor Wall, built in the 1930s to hold up downtown's Waterfront Park from the edge of the Willamette River, to collapse.12 Those who remember the 1996 floods, when citizens took up sandbags to keep the Willamette from overflowing onto the Harbor Wall, now witness the reverse happen in a matter of minutes, as the structural stability of the soil behind the wall is decreased to the point where it flows outward under its own weight, pushing into the river.
Buildings along the waterfront and in neighborhoods uphill are tottered at angles, edges of lower stories submerged into the ground, as the soil undergoes this catastrophic phenomenon. All throughout the liquefaction hazard areas, pavement and roadways have cracked and opened, as the ground beneath them spread outwards. Utilities are fractured all across the liquefaction areas, but the water system, being the oldest and largely still constructed of rigid cast iron, is the hardest hit. The moving soils snap the old pipe, and even newer plastic or ductile pipe is ripped apart at the seams.13 There are some 2,000 miles of water distribution pipe in the Portland metro area, and over the duration of the earthquake, it develops 1,150 breaks.14 Freshwater gushes to the service, mixing with sewage, from breaks in that system as well.
Portland's famous downtown bridges also falls victim to local geology, as liquefaction shifts the ground underneath them by more than a foot in places.15 The Broadway Bridge and the Morrison Bridge, both open drawbridges, suffer catastrophic damage to their concrete piers from cracking in the concrete as well, and each drop several spans after liquefaction moved their footholds an entire foot from their original location. Sheets of concrete weighing hundreds of tons crash into the river and onto the footings of the bridge, with sounds as loud as explosions.
The Steel Bridge, a century-old elevating drawbridge, was destroyed by its own counterweights as they swung back and forth during the five-minute quake, the twisting steel singing out in the spring air, as if one hundred years of history were escaping into the ether. A Union Pacific freight train crossing the bottom level of this bridge derails, its automobile carriers dragged into the water with the collapsing span, the noise adding to the deafening pandemonium filling the air. The Hawthorne Bridge, of similar elevating design, meets an identical fate.
The Burnside Bridge, the only seismically retrofitted of the surface street drawbridges, is also the only bridge that does not collapse. The County had installed restrainers to keep the spans from bouncing off their supports, and they worked as designed. But the approach ramps to the bridge were not retrofitted. While the bridge itself stands, the road needed to actually get onto the bridge has collapsed.
The two freeway bridges, the Fremont and the Marquam, both remain standing—proof that the retrofitting on the older Marquam was no waste of money. But like the Burnside, heavily damaged highway spans on the approaches to both bridges leave vehicles trapped above. Ironically, one of the ramps on the east side of the Fremont Bridge has fallen onto the Portland Bureau of Transportation depot, which lies directly underneath it.
By the time that the five minutes have elapsed, Portlanders find themselves transported to an entirely different city.
Portlanders driving in their cars swerve to avoid plummeting off the missing spans, piling into each other and the safety rails. The sound of an automobile crash in the impenetrable din is like a breath in a storm. Those who are seriously injured in the accidents on the bridges will most likely wait quite a while for medical help to reach them.
After what seems to be an eternity for those living it, the earth finally stills at 11:49 AM.
By the time that the five minutes have elapsed, Portlanders find themselves transported to an entirely different city. The roads that they know, the buses and trains, the bridges and freeways, and even the buildings in which they spend their days may still exist, but they also might not. The only way to begin to navigate this new city is to explore its dangerous, groaning, smoking terrain.
And this is what thousands of Portlanders begin to do, as they try to get from wherever it was they were when the earthquake began, to wherever their home might be, now that the earth is solid once more. I live in North Portland, and I imagine what my neighbors and I might see, attempting to escape downtown and return to our neighborhoods. Like everyone else who works downtown but lives on the east side of the river, the Willamette is now our first hurdle.
The brand new Tillikum Crossing public transit and pedestrian bridge survive in good shape—it was constructed to the highest seismic standard necessary for a CSZ quake, and was just completed in 2015. Many Portlanders make their way towards this bridge; they need to cross the river from downtown to the more residential east side quadrants. Public transportation ceases to exist in the chaos.
Cars are attempting to drive over the rubble, torn pavement, and around abandoned vehicles, but they are not making much headway. Some citizens try to drive onto the bridge, but pedestrians block their way and arguments break out. Perhaps it is the sobering sight of the fully collapsed Ross Island Bridge to the south that convinces people to abandon their cars and walk. It is good that they do not attempt to drive—after this bridge is checked by engineers, it will become the only functional crossing in downtown for the next several weeks.
I use the Tillikum Crossing, to make it over to the east side. Then I make my way north, walking a distance up from the industrial area by the river, which is full of old reinforced masonry buildings, and on ground at high risk of liquefaction. I have to tangle with the freeways, which cross the river from the Southwest, and head north to the I-84 and I-5 interchange.
In East Portland, the quadrants are divided almost exactly by deep freeway trenches. I-84 runs east-west, from the Willamette River to the east, separating most of the Northeast from the Southeast until 95th Ave. I-5 separates the North from Northeast as the freeway runs north-south from downtown north to the Columbia River. These trenched freeways, once the conduits of transportation around the city, now divide it.
The interchange of these two freeways on the east bank of the Willamette collapses, after its piers shifted under liquefaction.16 Parts of the complicated network of ramps are in the river, others elements sprawl onto the lower portions of the multi-level interchange, and across the train tracks where the tail end of the freight train derailed off the Steel Bridge sits stalled. Only by climbing down onto the freeway, climbing over the rubble and over the stalled train, am I able to get from the Southeast to the Northeast.
Down in the remains of the interchange, we see the crew of the Lloyd Center fire station, the closest station to the interchange not separated by bridges.17 The crew is working with volunteers who have abandoned their cars further up the freeway, to free trapped victims in the maze of highway rubble. Volunteers help the emergency workers all over the city, who are spread thin, given the vast number of emergencies instantly in progress.18
I want to stop and help, but the people crowding around them already look like they might be getting in the way as much as they're helping. And I'm eager to make it to my neighborhood, to see what has become of it, and what I can do there.
Along with many others, I set out on foot, through the Rose Quarter, looking for a math around the freeway collapses, which have come a labyrinth we now must wander. There are massive cracks visible in the concrete grain elevators on the Willamette. The Moda Center, where the Trailblazers play, has sustained little structural damage, but many windows are broken.
We walk on streets without traffic, too much pavement broken to allow passage, too many wires and utility poles down, too many bridges collapsed, too many abandoned vehicles on the streets. The traffic lights are dark anyway, betraying a general power failure.
So many transformer stations and delivery lines are down it is hard to pinpoint any particular spot of weakness, but all four major high voltage river crossings run by the Bonneville Power Administration, which manages much of the Pacific Northwest's grid, are built on liquefaction prone land.19
Even if transmission lines had not collapsed, somewhere around 6.5% of the load on the Northwest's grid disappeared during those five minutes, as buildings were disconnected in the shaking. The power grid automatically shut down to prevent generation spikes, and will take at least a day to sort out and repair, before any transmission can be resumed.20
It is possible that the grid shutdown will cause a cascading failure, spreading blackout to vast portions of the United States and Canada. But here in Portland, our cell phones are mostly without signal, and where we can get one, they are impossibly jammed. We have no idea what is happening in the rest of the country. The grid is broken both at its roots, and its branches.
We focus on where we are, in the here and now. Every block has obstacles, things to be avoided. We have no idea what is hazardous, and what is safe. Do we dare cross a bridge with cracked pavement? Is that an exposed gas line, a sewage line, or merely old pipe ejected from the ground? Do we stop to search through damaged buildings? When is a building too dangerous to enter? A thousand questions fill our mind, as we pick our way over our city.
Those of us trying to head north along the banks of the Willamette, close to the river to bypass the fallen the freeway interchanges, will see massive liquefaction damage. We cautiously walk underneath those piers of the Fremont Bridge that are still standing, by the Union Pacific switching yards, avoiding the approach ramps that have collapsed up the hill over N. Mississippi Ave.
Here the ground rises abruptly into the plateau of North Portland, and to proceed further we need to get up the hill, or we will be trapped against the river by the steep bluffs. The bluffs along the rail line running north to the Swan Island industrial area are a mess, riven with landslides. Intermittent slides cover Greeley Ave, below Overlook Park. Clamboring over a fallen overpass, we are able to get on Interstate Avenue.
Cresting the hill above the Park, we look out over the Willamette River to see a jaw-dropping sight—the north end of the river is on fire.
This fire is caused by a cascading string of failures at what is called the Critical Energy Infrastructure Hub.21 The single petroleum pipeline for the entire state of Oregon enters from southern Washington through this area, the CEI Hub, a six-mile long cluster of tank farms, port docks, natural gas facilities, and other petroleum processing apparatus along the bank of the Willamette River in Northwest Portland. Once the refined petroleum arrives at the Hub, it is converted into various petroleum products, and shipped out to other stations. The Olympic Pipeline, built in the 1960s, now has hundreds of breaks due to liquefaction.22 Thankfully, automatic shut-offs prevented a potentially massive explosion of the pipeline itself.
The tank farms fed by the pipeline are not as resilient. Half-full tanks developed standing waves known as "seiches," commonly seen in swimming pools during earthquakes.23 Like a bucket of water pushed back and forth, the liquid inside the tanks began sloshing, a massive amount of lateral force causing the tank sides to buckle and rupture. Containment walls are built around the tanks, meant to capture fuel spilled during accidents. But this area around the river is prime liquefaction area, and the walls and tanks sink and topple over, even before the flood of fuel hits them.24 Deluges of petroleum spread across the land and water. No one will ever know how the fuel first caught fire, so quickly the blaze spreads from tank to tank. The likely guess is fallen power lines.
The failures continue to cascade. Most of the fireboats are trapped, prevented from reaching the Hub by various collapsed bridges on the river. The only fireboat that can access the blaze is Station Six in the Northwest Industrial area, but it is now busy fighting a different fire along Front Street near the Fremont Bridge, attempting to keep it from spreading into the dense housing areas of the Pearl District on the west bank of the Willamette.25
The growing slick of petroleum on the river sends up vast clouds of black smoke, joining that of countless other fires burning around the city. But the smoke of burning petroleum is far more ominous: thicker, darker, unwilling to be dispersed into light wisps by the light southern wind, the state of Oregon's singular energy dependency rising to the heavens on a back of a black horse. The river of fire spreads to a yet-to-be-unloaded fuel tanker, currently drifting in the river after the pilings it was tied to came loose in the spreading river bottom. This ship of flame continues north, drifting downstream with the blaze, sailing shrouded into the dense smoke cloud.
Our eyes glazed at what we are seeing, we can only continue north along Interstate Avenue, amid abandoned cars and stalled light rail trains, both forms of transport blocked by fallen electrical wires.
I used to live on this street. I watched its transformation from a strip of neon-lit motels to a fashionable residential district, linked directly to downtown by light rail. One of the most eye-catching motel signs, with only a majority of its letters lit even in the best of times, has tipped over and deposited its luminous glass into the empty husk of a Prius, passing below it just at the wrong time. The driver must have made it out safely—they're nowhere to be seen.
The fancy new apartment buildings have held together, just barely, but the older brick court apartments and motels lie in ruins. I can't bear to see if my old, unreinforced masonry building is still standing, as I already know that it can't be. Instead, I cut east at Alberta Street, climbing down across the I-5 trench that cuts through North Portland, to make my way into Northeast Portland.
The freeway is blocked by collapsing overpasses, none of them seismically upgraded.26 The roadway is choked with abandoned cars, their drivers climbing the ivy-choked banks of the trench to escape, but to little avail. The exit and entrance ramps are jammed, as obstacles at the top quickly back a line of stalled cars down into the trench. The drivers are long gone, attempting to get home on foot as I am.
The neighborhoods of North and Northeast Portland vary in how they've fared, depending on construction and the particular liquefaction of the ground. Where the ground held together, and where the buildings were not made from brick, things are not so bad. Most of the buildings are completely habitable, but few escape superficial damage of some kind during the long, sustained shaking. Large picture windows have exploded from their frames.
The damage almost appears random, as if decided by the flip of a coin, but really stemming from invisible characteristics of construction. Classic wood frame Craftsman bungalows have slid off their foundations if not properly anchored to them. Tall, vintage Victorian houses have tipped, sunk into the liquefaction prone ground. But many houses just like them are standing, with merely a collapsed porch, or power lines ripped from the weathercap by falling branches, wires left lying in the yards. It is a terrible roulette outcome that we are apprised of, as we return to that one place where we assumed we were safe and secure.
Each of us, without exception, breaks into a run as we draw close, anxious to see if our own home is still standing.
Terraform editor Brian Merchant spoke to author Adam Rothstein about this series for Radio Motherboard, which is available on iTunes and all podcast apps.
1. While the "damage slight" prognosis doesn't sound so bad for the Portland area, a complicating factor is the long duration of a megathrust quake. The 1994 Northridge earthquake in LA, a relatively contained thrust fault quake, had a high intensity of IX but lasted no more than twenty seconds. The 2011 Tōhoku quake, a megathrust quake much more similar in character to a potential CSZ quake, lasted for a full six minutes.↩
2. The United States Geological Survey (USGS), and accordingly, the Oregon Department of Geology and Mineral Industries (DOGAMI) use several measures in predicting the potential forces a location may experience during an earthquake. The most general measure of earthquake force on buildings is Peak Ground Acceleration. This is equivalent to the G-forces on a piece of ground, pulling it horizontally. This is a good way to think about shear forces on the base of a structure.↩
3. Since 1986, California has had a law mandating the inventory of Unreinforced Masonry Structures, and many programs for conducting seismic upgrades. Portland is currently in the process of designing potential programs. Federal Emergency Management Agency, Unreinforced Masonry Buildings and Earthquakes (2009), 22; Portland Bureau of Emergency Management, "Unreinforced Masonry (URM) Seismic Retrofit Project," retrieved February 29, 2016 http://www.portlandoregon.gov/pbem/66306)↩
4. State of Oregon Building Codes Division, Earthquake Design History: A Summary of Requirements in the State of Oregon (2012), 4↩
5. Spectral Acceleration is a way of thinking of the forces on a building itself, which will naturally sway back and forth as the ground shakes below it, like a car's radio antenna rebounding after the vehicle screeches to a halt. However, SA affects different buildings in different ways. Think of a thin, short radio antenna, plinging like a string instrument. Then replace that with a long truck antenna, the thickness of a fishing rod. They both bounce, but in very different ways. This is why it is very difficult to predict which buildings will stand up to their own rebounding under the earthquake's shake, unless every building's characteristics are studied in detail.↩
6. Oregon Department of Geology and Mineral Industries, Earthquake Scenario and Probabilistic Ground Shaking Maps for the Portland, Oregon, Metropolitan Area, Interpretive Map Series IMS-16 (2000), Sheet 3.↩
7. Oregon Seismic Safety Policy Advisory Commission, Oregon Resilience Plan, 131.↩
8. DOGAMI has produced a number of maps identifying landslide-risk areas, but there is no way to tell which will hold and which will give way until the earthquake comes. Most of these areas are in the West Hills, above downtown on the west side of the city. But there are a number of buttes out in the east area of Portland as well, with wet soil held high above the streets and neighborhoods. Oregon Department of Geology and Mineral Industries, Statewide Landslide Information Layer for Oregon, retrieved February 29, 2015, http://www.oregongeology.org/slido/index.html ; also see http://www.oregongeology.org/pubs/ims/p-ims-033.ht... ↩
9. Oregon Seismic Safety Policy Advisory Commission, Oregon Resilience Plan, 32.↩
10. This casualty count in my scenario is only slightly higher than the Department of Homeland Security's (DHS) baseline study of the CSZ quake--which many state and local agencies use as their own baseline. The DHS study uses Federal Emergency Management Agency (FEMA) software called Hazus to estimate damage. While Hazus can factor landslide risk and liquefaction into its estimates, the DHS study drew its casualty estimate from effects of shaking only. And so I have added, solemnly, one hundred more deaths, and one thousand more injuries to their projected total, as a conservative estimate of the compounding effects of a major landslide in a populated area, as well as rampant liquefaction. Department of Homeland Security, Draft Analytical Baseline Study for the Cascadia Earthquake and Tsunami, (2011), 32; Also see Oregon Department of Transportation, Oregon Highways Seismic Plus Report, (2014), 34. ↩
11. Liquefaction is another destructive factor that can't be measured by PGA or SA directly. When sandy soil is saturated with water--like along a river or where the water table is high--and then subjected to an earthquake's shaking, the force that allows the individual grains of earth to support weight like a solid object is diminished. The water moves between the grains as if lubricating them, and the soil flows like a liquid. DOGMAI and the City of Portland have published detailed liquefaction risk maps, and while nearly all of the waterfront areas are at high risk, so too are much of North Portland, and vast swathes of the Northeast and Southeast. Building codes in Portland only began to take liquefaction risk into account in 2004 (see Oregon Department of Geology and Mineral Industries, Earthquake Risk Study for Oregon's Critical Energy Infrastructure Hub, 96), so many structures are vulnerable. ↩
12. City of Portland, Earthquake Response Appendix (2102), 4.↩
13. Oregon Seismic Safety Policy Advisory Commission, Oregon Resilience Plan, 204.↩
14. Portland Water Bureau, "System Basics," retrieved February 29, 2015 https://www.portlandoregon.gov/water/article/216797; Oregon Seismic Safety Policy Advisory Commission, Oregon Resilience Plan, 224.↩
15. The Portland Bureau of Transportation, the Oregon Department of Transportation, Multnomah County, and other agencies share responsibility for the many picturesque bridges over the Willamette downtown. They each have separate seismic reports, but most useful for making these determinations were Multnomah County's Division of Transportation Seismic Evaluation Reports for the Burnside, Morrison, Hawthrone, and Broadway Bridges (1995, 1995, and 1996 respectively); Department of Homeland Security, Draft Analytical Baseline Study for the Cascadia Earthquake and Tsunami, 10; Oregon Seismic Safety Policy Advisory Commission, Oregon Resilience Plan 37-8; Oregon Department of Transportation, Seismic Vulnerability of Oregon State Highway Bridges 28, 52; City of Portland, Earthquake Response Appendix, 5. ↩
16. Department of Homeland Security, Draft Analytical Baseline Study for the Cascadia Earthquake and Tsunami, 88↩
17. The fire station itself only survived because all of the Portland station houses recently received seismic upgrades, completed in 2012. Oregon Seismic Safety Policy Advisory Commission, Oregon Resilience Plan, 80.↩
18. Oregon Office of Emergency Management, State of Oregon Cascadia Subduction Zone Catastrophic Earthquake and Tsunami Operations Plan (2012), 4-6.↩
19. Michael Beaty, et al., "Seismic Evaluation of Transmission Tower Foundations at River Crossings in the Portland-Columbia River Region," Tenth U.S. National Conference on Earthquake Engineering, 2014.↩
20. Department of Homeland Security, Draft Analytical Baseline Study for the Cascadia Earthquake and Tsunami, 41.↩
21. Oregon Department of Geology and Mineral Industries, Earthquake Risk Study for Oregon's Critical Energy Infrastructure Hub ↩
22. Department of Homeland Security, Draft Analytical Baseline Study for the Cascadia Earthquake and Tsunami, 61. ↩
23. Oregon Department of Geology and Mineral Industries, Earthquake Risk Study for Oregon's Critical Energy Infrastructure Hub, 96. ↩
24. Department of Homeland Security, Draft Analytical Baseline Study for the Cascadia Earthquake and Tsunami, 68.↩
26. Oregon Department of Transportation, Oregon Highways Seismic Plus Report, 38↩