Devil's Mountain Fault: the frightening implications for Victoria
By David Broadland, March 1, 2016
Scientists recently confirmed an active seismic fault that could generate a large earthquake lies within 5 kilometres of downtown Victoria.
LAST JUNE THE Geological Survey of Canada quietly released a report on a previously unexplored deformation in the bedrock below the Strait of Juan de Fuca—the Devil’s Mountain Fault. When I first read the report a few weeks ago, Sir James Douglas’ well-mythologized first impression of this place leaped to mind. On his arrival in 1842 Douglas had pronounced it “a perfect Eden.” It now appears he was profoundly mistaken.
Lurking in the strait just 5 kilometres from downtown Victoria, according to scientists, is a physical imperfection so great that one day this “perfect Eden” could become—over the span of 10 or 20 seconds—hell on Earth.
Before the scientists’ report was put on Natural Resources Canada’s website, John Cassidy thought it would be best to alert Emergency Management BC. Cassidy is the head of the Earthquake Seismology Section of the Geological Survey of Canada (GSC) at the Pacific Geoscience Centre in Sidney. What was in the report that Cassidy thought EMBC should know about? The alert to EMBC was titled “Discovery of potentially active submarine faults near Victoria, BC.”
The senior scientist on the study, the GSC’s Dr Vaughn Barrie, assisted by marine scientist Dr Gary Greene, had analyzed sediment cores and multibeam bathymetry scans of bedrock below the strait in an area just southeast of Victoria. From this data Barrie was able to create a 3D map of a short section of the Devil’s Mountain Fault Zone. The Devil’s Mountain Fault is a deep crack in the Earth’s crust that runs for about 125 kilometres from near Darrington in the foothills of the Cascade Mountains in Washington to just south of Victoria. Before Barrie’s analysis, any estimate of the danger the fault might pose to Victoria would have been speculative. Previous calculations based on the presumed length of the fault had suggested that if it ruptured along its full length, an earthquake of magnitude 7.5 could be generated. But did the fault actually come close to Victoria?
The work of Barrie and Greene confirmed a potentially grave risk for Victoria. In the summary of their report they stated, “Based on recently collected geophysical and sediment core data, the western extent of the active Devil’s Mountain Fault Zone has been mapped for the first time, offshore the city of Victoria. The occurrence of this active fault poses the real possibility of an earthquake, similar to the devastating 2011 Christchurch, New Zealand earthquake, occurring near the city of Victoria.”
Barrie noted that the 2011 Christchurch earthquake killed 185 people and caused damage assessed at $40 billion (NZ). He observed that earthquake “had an effective magnitude of 6.7 and was approximately 5 kilometres from central Christchurch at its closest approach…” The scientist noted that “the Devil’s Mountain Fault Zone is less than 5 kilometres from central Victoria” and “appears to have the potential of producing a strong earthquake adjacent to Victoria, perhaps as large as magnitude 7.0 or greater.”
Barrie's confirmation of the close proximity of an active fault to central Victoria was alarming news. Previous loss estimates for a hypothetical magnitude 7.0 earthquake on the Leech River Fault—located further away from Victoria than the section of the Devil’s Mountain Fault that Barrie had mapped—predicted 1500 fatalities in the CRD, with close to 20,000 injuries, many of which would require hospitalization. Over six million tons of debris would be generated by collapsed and damaged buildings and other structures. But the Leech River Fault has shown no signs of activity during the last 10,000 years. Living beside it is like having a bomb in our basement, but a bomb which we believe has had all the explosive material removed. Barrie, in effect, confirmed the Devil’s Mountain bomb is in our living room and could go off at any moment.
To put Barrie’s finding in perspective, consider the so-called “Big One.” That’s the commonly-used expression to describe what geoscientists call a great-plate boundary earthquake; it’s also known as a “Cascadia Subduction Zone event.” Scientists estimate that a full-length rupture of the 1100-kilometre-long subduction zone along North America’s west coast could produce a magnitude 9.0 earthquake. Although a magnitude 9.0 earthquake off the west coast of Vancouver Island would release over 1000 times more energy than a magnitude 7.0 earthquake, because of its much greater distance away from Victoria, such an event would cause only about half the casualties and property damage that a magnitude 7.0 shallow crustal earthquake immediately adjacent to Victoria would cause. A rupture of the Devil’s Mountain Fault could have twice the impact on Victoria as the Big One.
Although Focus has been unable to obtain a loss estimate (casualties and property damage) for Victoria from Natural Resources Canada for "the Big One," a study done by BC geoscientist Martin Zaleski reported that Victoria would sustain much greater damage from a nearby magnitude 7 earthquake than from a magnitude 9 Cascadia subduction event. When asked about Zaleski's finding, Cassidy said, "That's about right."
So Cassidy and his colleagues at GSC knew that when Victorians heard about this nearby existential threat, there would be questions.
Before Dr Barrie’s report was placed online, Cassidy contacted EMBC and outlined the potential threat—what was known and what wasn’t. EMBC then arranged a conference call with about 100 participants—primarily emergency management organizations and local governments from across the South Island and Lower Mainland regions. Cassidy explained to Focus that this step was taken because of “potentially significant interest.”
The information Cassidy shared with those emergency management stakeholders included caveats about the scientists’ report. For example, the study has not been internationally peer-reviewed and more research would need to be done to confirm Barrie’s conclusions.
The “potentially significant interest”—beyond that expressed by the 100 or so participants in the conference call—never materialized. That’s probably because no one outside of the conference call ever found out about the report—until now.
Living with the bomb
Cassidy told Focus that the results of additional research on the Devil’s Mountain Fault Zone will be ready “in about a year.” One of the unresolved issues Dr Barrie noted in his study was the possibility of a connection between the Devil’s Mountain Fault and the Leech River Fault. Barrie’s report stated, “The data here does not suggest any connection between these faults, though they are separated by only five kilometres. Further data are required to the west of our survey data set examined here to determine any relationship between these fault zones.”
On a large-scale map the two faults appear to run directly into each other and the concern is that a longer fault could generate an even more powerful earthquake. But Cassidy said there is no on-the-ground evidence that the Leech River fault has been active since the last period of glaciation ended, about 9,000 years ago. That, he said, makes it less likely that the active fault Barrie confirmed would be connected to the Leech River Fault.
Dr Barrie’s report includes excerpts from previous studies and one of the most interesting of his references is this: “Hyndman et al (2003) estimated a recurrence interval for large upper-plate fault earthquakes of magnitude 7.0 and greater in the Puget Lowland-Georgia Strait region to be about 200 years…They suggested that additional large earthquakes in the upper plate may occur in this region shortly after great-plate boundary earthquakes.”
Translation: Magnitude 7.0 and greater crustal earthquakes in the region where we live are not that uncommon. And, a rupture of the Cascadia Subduction Zone could be followed “shortly” afterward by a rupture of the Devil’s Mountain Fault.
Talk about a nightmare scenario. The Big One would cause widespread damage throughout the Pacific Northwest, including Vancouver and Seattle, so Victoria couldn’t expect help from nearby communities. Then comes the Really, Really Big One...
The BC Earthquake Immediate Response Plan doesn’t cover that scenario. The plan is the responsibility of the previously-mentioned Emergency Management BC, a provincial agency that falls under the control of Attorney General Suzanne Anton. EMBC’s plan is contained in a 127-page document that lists actions to take when a damaging earthquake occurs, such as activating the “Mass Fatality Plan.”
The plan’s scenario for a magnitude 7 shake in Victoria considers the “worst case” to be a mid-afternoon shallow crustal earthquake in January following a 3-day Pineapple Express. The ground would be saturated and prone to liquefaction. Here’s what the planners imagine would happen:
“For many, the earthquake is heard before it is felt. The low, rumbling sound is similar to that of a freight train, immediately followed by 10 to 20 seconds of violent shaking that knocks people located closest to the epicentre from their feet—except for those who remember to ‘drop, cover, and hold on.’ Taller buildings sway with the high intensity shaking. Unsecured objects fall or fly through the air. Roads crack and the ground ruptures in some areas. Buildings on softer soils lose support through liquefaction. Landslides and rock falls are generated in many areas, cutting off transportation routes. Flooding is increased by the recent wet weather event with some dikes failing. Several fires start throughout the impact area from damaged electrical power and gas lines. Some buildings collapse, many shift and crack, and others are destroyed by fire.
“Windows break and glass scatters across the pavement. Debris is strewn throughout roadways, cutting off access to areas. Entire walls from unreinforced masonry buildings fall into the streets. Many of those who try to run outside suffer extreme injury or death from falling and flying objects and thousands are trapped or injured. Dust, smoke and sirens fill the air.”
Hopefully, The Plan itself won’t be buried under broken blocks of granite and marble at the seismically vulnerable legislative buildings on Belleville Street before the Mass Fatality Plan can be activated. But don’t count on it. The Province committed $1.5 billion in 2005 to an upgrade of vulnerable schools in Victoria and Vancouver but has taken no steps on the estimated $300 million seismic rehabilitation of the 118-year-old Parliament Buildings. Local governments may have plans, but they have little or no money for making this region more seismically safe and resilient.
Although one might think that making the region more seismically safe and resilient would be a simple matter of applying science and common sense to the problem, recent events illustrate that there's not much of either at work.
Confused public-safety priorities
A genuine and concerted effort to reduce Victoria’s exposure to seismic risk—significantly higher than any other city in Canada (see table below)—will require public investment in education, prioritization, emergency response and infrastructure renewal. It’s astonishing, then, that Barrie’s dramatic and revelatory report on the Devil’s Mountain Fault was relegated to an obscure corner of Natural Resources Canada’s website even while Victorians struggled to respond to a controversial “high risk” classification of a different sort.
Under federal regulations imposed on Victoria’s marine disposal of liquid waste, the region is contemplating spending upwards of $1 billion to convert to a land-based system. Yet six past and current public health officers have stated: “There is no measurable public health risk from Victoria’s current method of offshore liquid waste disposal.” Those health officers are Dr Richard Stanwick, Dr John Millar, Dr Shaun Peck, Dr Brian Emerson, Dr Brian Allen and Dr Kelly Barnard.
A recent peer-reviewed study by DFO scientists found that spending billions of dollars upgrading sewage treatment in Vancouver and Victoria would have “negligible effect” on environmental conditions in the Salish Sea.
If there’s no risk to public health or the environment from a marine-based treatment system—but the Devil’s Mountain earthquake could hit at any moment killing or injuring thousands of Victorians—what are we to make of the federal government’s priorities?
The challenge to making the region more seismically safe and resilient isn't just a question of correctly prioritizing seismic vulnerability in relation to other needs, however. The evidence accumulated during the Johnson Street Bridge Replacement Project is illustrative of how difficult it can be for local government to properly assess seismic risks for different structures, and then to ensure that the risk for any one structure is adequately addressed.
In the case of the bridge project, where the City of Victoria was responding to the existing bridge's apparent seismic vulnerability, City Council chose to build a new bridge before it had addressed the known seismic vulnerability of its main fire hall. The City had been told the fire hall would collapse in an earthquake and trap emergency response vehicles. At the same time, councillors justified replacing the bridge partly on the basis of ensuring that emergency vehicles would be able to circulate immediately following an earthquake. Common sense eluded councillors:If rescue vehicles were trapped in a collapsed fire hall they wouldn't be able to use the bridge. The political attraction of building a glamorous signature bridge designed by an internationally-renowned architect won the day.
At the same time, a seismic assessment of 16 City-owned buildings showed many were potential death traps. The engineering assessment by Read Jones Christoffersen was kept secret during the bridge decision-making process and wasn’t made public until Focus obtained it in an FOI and published the details here. The assessment didn’t even look at some of the most vulnerable structures, including Downtown parkades and City Hall. The potential for loss of life from the collapsed City-owned buildings was much greater than from a collapsed Johnson Street Bridge.
Unbelievably, the bridge the council choose to build—in response to the existing bridge’s seismic vulnerability—will, it turns out, likely suffer “permanent loss of service” in an earthquake generated by the Devil’s Mountain Fault. The story of just how a project aimed at increasing seismic safety could, instead, produce a seismically vulnerable design, is a warning that local governments are badly in need of an independent, trustworthy, publicly-funded agency to help guide the region toward seismic safety and resilience. In light of Barrie's warning about the Devil's Mountain fault, the failure to create a seismically resilient bridge is a cautionary tale that needs to be thoroughly understood. In this case, the devil really is in the details.
How Victoria got a “less robust” bridge
In 2009, following receipt of an engineering report that recommended the Johnson Street Bridge be seismically upgraded, Victoria City council voted to replace the bridge instead. In seeking federal funding for the project, then-Mayor Dean Fortin wrote then-Federal Minister of Transportation and Infrastructure John Baird, telling him: “Any seismic event will bring it down.”
In 2010, after being forced to seek approval for its proposed bridge in a referendum, the City was advised that, whether it chose to repair or replace the bridge, it should spend additional money to insure both would withstand a “magnitude 8.5” earthquake. A presentation to City of Victoria councillors by MMM engineer Joost Meyboom on June 14, 2010 stated there was a “35 percent probability of a major quake (magnitude 7.0 to 7.9) in the next 50 years.” Meyboom recommended that a new bridge “be designed for a magnitude 8.5 earthquake.” He told councillors, “If you’re going to spend $100 million on a facility, the premium to pay for a very high seismic performance is a relatively low price for insurance.” The City agreed to buy this level of seismic protection.
A few months later, just before a referendum on a new bridge, a study by scientist Chris Goldfinger noted that Cascadia subduction zone earthquakes could be as strong as magnitude 9.0. Meyboom wrote the City and suggested it should consider protecting the bridge to magnitude 9.0; he told the City that a higher level of protection would cost more money. This was a highly revealing moment. Meyboom equated the maximum seismic vulnerability of the bridge to the Cascadia subduction hazard, an assertion that was untrue. I’ll come back to this later. Shortly after Meyboom's attempt to upsell the City on higher seismic protection, the referendum on the new bridge passed.
Fast foward to mid-2012. The City had needed to raise the bridge project's budget from $77 million to $93 million and was in the procurement phase. Councillors were adamant the budget would go no higher. There were three potential bidders. As part of the procurement process, the City asked each company to provide an initial opinion on whether it could build the bridge to the specified criteria on the City’s budget. All three said “No.” A short time later, MMM Group provided the companies with a document that established a lower level of seismic performance for the new bridge, thereby reducing expected costs. This document eventually became part of the contract the City signed with PCL, the winning bidder, but its addition to the bid process was kept secret from all but senior managers. Councillors were not informed.
The document described how the bridge was expected to perform in three different earthquake scenarios. The strongest earthquake covered by the design criteria was approximately equivalent to a magnitude 7.5 earthquake. For that event, the seismic performance specified was “possible permanent loss of service”—which implies damage so great that the bridge would need to be replaced.
The time between when an earthquake occurs and when emergency response vehicles can circulate is critical to rescue and recovery operations. The revised seismic design criteria specified this time for earthquakes smaller than magnitude 7.5, but no level of access was described for a magnitude 7.5 shake. The document provided no information whatsoever about the allowable outcomes—damage or emergency vehicle access—for a magnitude 8.5 earthquake, the level of seismic protection the City had agreed to buy.
(The Seismic Design Criteria document does not express earthquake strength as "magnitude." Rather, it uses "return period." But during the decision-making process on the bridge, engineering firm Stantec linked specific magnitudes with specific return periods. I am using Stantec’s conversions in this article.)
The revised seismic design criteria were kept secret until Focus obtained the document in an FOI. About a year ago, I wrote a story about how the new bridge had been designed and constructed to a much lower level of seismic protection than had been recommended to the City by Meyboom in 2010. I related the fact that the bridge could suffer permanent loss of service in a magnitude 7.5 earthquake.
Two months later, I filed an FOI for the communications between the City and MMM that resulted from my article. The documents obtained showed that the company that designed the lifting portion of the bridge, Hardesty & Hanover, did not deny the bridge could suffer permanent loss of service from a magnitude 7.5 earthquake. The record of communications showed no one seemed to know how the seismic design criteria had been lowered, or who had promised what. Confusion reigned over the project. One MMM official called the matter a “debacle.” (This is perhaps the most accurate statement made by an MMM employee about the seismic issue in the 7 years the project has run.)
The City’s former director of engineering, Dwayne Kalynchuk, confirmed to Focus that Hardesty & Hanover had used the reduced seismic design criteria to design the bridge.
Several months later, the bridge project director Jonathan Huggett informed councillors that the new bridge would be “somewhat less robust” than the existing, 93-year-old bridge.
Recall that at the beginning of this account, then-mayor Fortin had described the existing bridge to John Baird, writing “Any seismic event will bring it down.” Taking Fortin and Huggett at their words, we would have to conclude that “Any seismic event” would bring down the “less robust” new bridge, too.
So there’s strong evidence that, after spending $140 million (this is the most likely current price based on information provided by the City about cost increases) on a new bridge because the old one was seismically vulnerable, there will be little or no increase in the seismic safety of the bridge.
Issue too complex for local politicians?
Dr Barrie’s discovery of a large, active fault just a few kilometres from the Johnson Street Bridge highlights the need for more effective management of Victoria's seismic vulnerability by elected officials and civil servants. A better understanding of seismic issues by everyone involved in making decisions about critical public infrastructure seems key.
The primary misstep in the case of the bridge was the choice of a seismically-risky design. The section of the new bridge that lifts—the bascule leaf—is not permanently attached to the bridge’s foundation. It floats on steel rollers and depends on intermittently-engaged span locks to hold it in place during an earthquake. Who would build a house in Victoria without ensuring it was permanently anchored to its foundation?
Although at least one of the companies competing to build the bridge red-lined the seismically risky design to City staff in its bid, that company’s proposal was heavily penalized for not sticking with the flawed design concept. Those staff also hid that criticism from elected decision-makers. So bad design and failure to listen were factors in the debacle.
What else? Several paragraphs back I mentioned that the City's consultant, Joost Meyboom, had suggested to the City that since a Cascadia Subduction Zone event could produce a magnitude 9.0 earthquake, the City should consider spending more money to protect against that.
That incident seems to suggest Meyboom thought a subduction event—the Big One—was the defining seismic design consideration.
But a couple of years after Meyboom’s magnitude 9.0 pitch, an MMM document noted: “Given the location of the bridge, the Cascadia Subduction Earthquake was also considered as an important event. A comparison of site specific response spectra, however, showed that the spectral acceleration[s] for the Cascadia event are lower than the 1 in 475 [year] earthquake and this is therefore not a critical design consideration.”
Meyboom misunderstood, apparently, what kind of seismic event the bridge needed to be designed to withstand.
The big problem with that was that when Meyboom first made recommendations to City councillors about seismic protection, councillors relied on his advice to make critical decisions. Unfortunately, councillors made no attempt to insure they were getting solid advice. They should have asked for at least one other opinion from a source unaffected by whether the project went ahead or not.
Once the lowered seismic design criteria were made public by Focus, the City ought to have pursued the matter with an independent investigation. Instead, it simply sought reassurances from Meyboom's company. The City’s unwillingness to properly investigate whether the bridge had been built to a lower level of seismic performance than it had agreed to pay for could, one day, have serious consequences for public safety and economic recovery. In that respect, City managers and councillors abrogated their fiduciary responsibility to the public.
Barrie's report brings into public view the need for much more attention being paid to seismic safety and resilience in the region. One possible solution to the kind of problems experienced with the bridge project would be for the region to develop its own seismic safety planning and prioritization agency. The work of such a body would need to be informed by science, not engineering companies working in the construction industry. Until the region develops such capacity, it’s unlikely to make progress toward reducing the number of casualties and property loss that will come one day when Devil’s Mountain Fault ruptures.
David Broadland’s father Bob was on his parents’ farm 30 miles from the epicentre of the magnitude 7.3 Vancouver Island Earthquake in 1946. Bob’s mom thought an atom bomb had been dropped. Bob’s father Tom experienced the magnitude 7.2 Vancouver Island Earthquake in 1918. So far, David’s biggest earthquake was the magnitude 5.3 shake Victorians felt in 1976. But the party ain’t over yet.
|GSC Devil's Mountain Fault analysis 2015 06.pdf||5.13 MB|
|Alert sent to EMBC by GSC.pdf||273.01 KB|
|BC Earthquake Immediate Response Plan.pdf||3.37 MB|
|JSB Seismic Design Criteria Aug 17, 2012.pdf||96.24 KB|
|Initial JSB seismic design criteria in MMM PDR.jpg||264.08 KB|