Special Report: New study identifies earthquake hazards for Hartley Bay, Bella Bella, Kitimat and Terrace

UPDATED with comments from District of Kitimat, Terrace and the Gitga’at Nation

A preliminary seismic hazard assessment by Natural Resources Canada has identified possible earthquake scenarios for the Douglas Channel near Hartley Bay, Terrace and Bella Bella.

The same studies indicate that while Kitimat may not be directly in a seismic zone prolonged earthquakes cause some damage in Kitimat depending on the earthquake and the condition of the soil in certain parts of the District. One model scenario says that in the event of a magnitude 8.0 earthquake off the west coast of Haida Gwaii, given certain soil conditions, there might actually be more damage in Kitimat than on the islands.

Susceptibility to landslides

That assessment, part of the overall the study by the Geological Survey of Canada indicates that the north coast of British Columbia from Prince Rupert to Bella Bella is likely face to “seismically induced ground failure”– mostly landslides.

Overall, the report says that on a scale of 1 to 6 (6 representing the highest
susceptibility), the majority of the west coast of BC “exhibits landslide susceptibility values of 5 to 6, which is significantly higher than the rest of Canada.”

Geological Survey of Canada map showing parts of Canada that are prone to landslides. The BC North Coast study area is outlined by the rectangle. (Geological Survey of Canada)
Geological Survey of Canada map showing parts of Canada that are prone to landslides. The BC North Coast study area is outlined by the rectangle. (Geological Survey of Canada)

In British Columbia the landslides are most likely to be triggered by delayed melting of the annual snow pack, heavy rains, bank erosion and site loading and caused long-lasting damning of the river causing “damage to pipelines, rail, and forestry, as well as fish habitats.”

So far no recent landslides along the northern British Columbia coast are known to be caused by earthquakes, the reports say “the existence of numerous landslides strengthens the likelihood of seismically induced ground failures… due to the high levels of seismicity….it is expected that the increased likelihood of strong ground shaking (with long durations) will increase the landslide susceptibility.”

New studies

It was only after the 2012 Haida Gwaii earthquake and with what the Geological Survey of Canada calls “a growing number of on-going and planned infrastructure projects, BC’s north coast is emerging as a region of high strategic importance to Canada’s economy,” that studies began in area where “there has been minimal research to understand earthquake hazards.”

Now that studies have begun the Geological Survey has given the region its own new acronym BCNC (BC North Coast). Haida Gwaii is not part of BCNC, although earthquakes on those islands would likely impact the coast.

A Geological Survey of Canada map showing the BC North Coast region with earthquakes identified prior to and during recent studies. (Geological Survey of Canada)
A Geological Survey of Canada map showing the BC North Coast region with earthquakes identified prior to and during recent studies. (Geological Survey of Canada)

The Geological Survey says that historically “the BCNC has been seismically quiescent.” As a result “seismic monitoring and research related to the BCNC has been minimal.” That meant while larger earthquakes were “felt and recorded,” the configuration of the Canadian National Seismograph Network did not allow earthquakes less than approximately magnitude 2.1 to be monitored in northern BC.

Now the Geological Survey is looking at “long-term, continuous monitoring of micro seismicity, combined with geodetic and paleo seismic techniques” that could be used to study at the possibility of large earthquakes, including a possible fault on the lower Douglas Channel.

Since the studies began in August 2014, the Geological Survey identified 145 earthquakes within the study area, many too small to be felt since they are less than magnitude 2.0. Those earthquakes, however, were picked up by the new and improved instrumentation used by the earthquake monitors.

The two reports one on “seismic hazards” and the second on “geohazards” says five “temporary seismonitors”  (download reports from links below) were installed within the BCNC while some older stations were upgraded, saying, “It is expected that these new stations will be aid in locating small earthquakes” that were not previously detected by the existing network. The Geological Survey also installed ground movement monitoring GPS units along the coast.

The use of the term “temporary” raises the question about how much ongoing monitoring is planned.

The study also notes that the current data is not included in the seismic standards in the current National Building Code of Canada, which in turn is based on the Natural Resources Canada Seismic Hazard Map. That may mean that municipalities in the BC North Coast region, in the future, as the seismic studies continue, may have to consider updating building codes, especially in areas of “softer soils” as opposed to harder rock.

“Fault-like structure” on Douglas Channel

Detail of a map from the Geological Survey of Canada where the red line shows the 60 kilometre possible (still unconfirmed) fault line running from Gribbell Island to Princess Royal Island (Geological Survey of Canada)
Detail of a map from the Geological Survey of Canada where the red line shows the 60 kilometre possible (still unconfirmed) fault line running from Gribbell Island to Princess Royal Island (Geological Survey of Canada)

Over the years some small earthquakes have also been recorded on what the Geological Survey calls the “recently mapped fault-like structure” on Douglas Channel which was discovered in 2012. The survey is still calling it “fault-like” because it has not yet been confirmed as an active fault. A new map in the study shows that the “fault” runs from the southern tip of Gribbell Island, down the centre of Whale Channel east of Gil Island and then along the western coast of Princess Royal Island.

The study identified “a small, unfelt swarm of earthquakes between magnitude 1.7 and 2.0 between September 13 and 14, 2010 near Gil Island.”

There is also the previously identified ancient Grenville Channel Fault (ancient and believed inactive because it dates from the Cretaceous, the age of the dinosaurs) that runs from along Grenville Channel from Porcher Island in the north to Klemtu in the south which has experienced small earthquakes.

The report says geological studies of the Douglas Channel “fault-like structure” are a priority because, “Should this structure be determined to be an active fault, it would pose significant risk of earthquake-triggered landslides (and subsequent tsunami) from the susceptible Douglas Channel hill slopes.”

Clay and sand in Kitimat

The report also calls for more studies the local geology and soil conditions in the Kitimat Valley. A study back in 1984 by John Clague of Simon Fraser University showed that as the glaciers retreated during the last Ice Age there were “periods of stagnation” resulting in sediments that are thicker than other regions of British Columbia, Clague reported that in parts of Kitimat, the glacial moraine is hundreds of metres thick.

After the glaciers were gone, the sea levels rose and glaciomarine sediments (clay, silt up to 60 metres thick) were deposited until the sea level fell to present-day levels. The report says that as these marine deposits were exposed to fresh water, salts were leached out resulting in saturated, porous sediments, including clay, which are prone to failure. Boreholes in the Kitimat area show that the clay and sediments above the bedrock can range from 17 metres to 106 metres.

The report notes the presence of clay soils “can amplify ground shaking and secondary effects” as happened in November 1988 when there was an earthquake in the Saguenay region of Quebec.

Originally reported as a 6.2 magnitude but later downgraded to 5.9, on Nov. 25, 1988, the major earthquake was centered near the Quebec cities of Chicoutimi and Jonquière, with aftershocks felt as far away as Toronto, Halifax and Boston. The quake lasted for two minutes, catching thousands of people off guard and leaving buildings damaged and power out for hundreds of thousands of Quebecers.

CBC Television reported the earthquake caused a leak of toxic gas at the Alcan Aluminum plant at Jonquière, which was quickly contained. “There was no wind, we were basically lucky,” Alcan spokesman Jacques Dubac told CBC News at the time. 

Terrace earthquake

The report says the most significant event within the BC North Coast study region (which as mentioned doesn’t include Haida Gwaii) was a magnitude 4.9 earthquake approximately 20 kilometers southwest of Terrace on November 5, 1973, which was felt as far as 120 kilometers away, with some minor damage (broken windows and cracked plaster) reported near the epicentre. The main shock at Terrace was preceded by a magnitude 2.5 foreshock four hours before, and followed by a felt magnitude 3.7 aftershock the next day.

Bella Bella at risk

Another area most at risk, according to the report, is southern part of the BC North Coast zone, near Bella Bella, which is close to the northern section  Cascadia Subduction Zone  a “1,000 kilometre long dipping fault that stretches from Northern Vancouver Island to Cape Mendocino California” which one day will cause a major earthquake along the fault.

Cascadia subduction zone (USGS)
Cascadia subduction zone (USGS)

The report says that a magnitude 9.0 or higher earthquake in the northern Cascadia Subduction zone close to Bella Bella would be similar to the March 2011 earthquake in Japan and the 1964 Good Friday earthquake in Alaska.

For the northern part of the BC North Coast region, hazards could come from either a major earthquake off Haida Gwaii or a similar earthquake in south-eastern Alaska.

The greatest hazard would come from “long period” earthquakes greater than magnitude 6.75 with an epicentre between 300 and 350 kilometers away where the shaking lasts longer than one second.

The Geological Survey modeled three possible scenarios for major earthquakes in the BC North Coast Region.

Model #1. A magnitude 8.0 Earthquake at Haida Gwaii

The Geological Survey Canada model for an 8.0 magnitude earthquake west of Haida Gwaii. The possible damage is colour coded in the table below the map according to the Modified Mercalli Intensity Scale (Geological Survey of Canada)
The Geological Survey Canada model for an 8.0 magnitude earthquake west of Haida Gwaii. The possible damage is colour coded in the table below the map according to the Modified Mercalli Intensity Scale.  The red polygon represents the area of possible rupture in the model with the star representing the epicentre. (Geological Survey of Canada)

The model looked at a “plausible maximum predicted” magnitude 8.0 thrust fault earthquake off the west coast of Haida Gwaii which would be twice as strong in the fault area as the 7.8 quake on October 28, 2012 (Remember Magnitudes are based on a logarithmic scale. That means for each whole number higher, the amplitude of the ground motion recorded by a seismograph goes up ten times so magnitude 8 earthquake would result in ten times the ground shaking as a magnitude 7 earthquake)

For a short period earthquake, the report estimates that there would be minimal damage on Haida Gwaii similar to the damage from the 2012 earthquake with little or no damage on the BC North Coast.

A long duration, long period earthquake that lasted longer than one second and up to three seconds or longer “may effect taller structures and trigger ground failure (that is liquefaction and lateral shaking).” Kitimat would feel that earthquake with the worst shaking in parts of the District with what the report calls “sensitive soils.” Coastal islands would feel double the amount of shaking as would occur in Kitimat.

Model #2. A magnitude 7.2 Earthquake in Douglas Channel

 The Geological Survey Canada model for a 7/2 magnitude earthquake in the lower Douglas Channel. The possible damage is colour coded in the table below the map according to the Modified Mercalli Intensity Scale. The red star represents the possible epicentre. (Geological Survey of Canada)

The Geological Survey Canada model for a 7/2 magnitude earthquake in the lower Douglas Channel. The possible damage is colour coded in the table below the map according to the Modified Mercalli Intensity Scale. The red star represents the possible epicentre. (Geological Survey of Canada)

The second model looked at an earthquake in Douglas Channel based on the “fault like structure” if a slip strike rupture occurred along the entire 60 kilometers of the so far unconfirmed fault, resulting in a 7.2 magnitude earthquake. There would be very strong shaking within 20 kilometers radius of the epicentre, with moderate to heavy damage” in the relatively uninhabited islands, major shaking in Hartley Bay, resulting in very strong to strong damage at Hartley Bay and strong to moderate damage in Kitimat.

That earthquake, however, would be felt across the entire province of British Columbia. The report notes:

The expected effects and impacts of such an earthquake would mimic those of the 1946 magnitude 7.3 Vancouver Island earthquake, which occurred slightly west of Courtney and Campbell River. Shaking due to the 1946 earthquake was felt as far as Prince Rupert, BC to the north and Portland, Oregon to the south. In addition to knocking down 75 per cent of the chimneys in the local area, much of the earthquake-related damage was due to landslides, slumping and liquefaction

Model #3  A magnitude 6.3 Earthquake near Terrace

 The Geological Survey Canada model for an 6.3 magnitude earthquake southwest of Terrace. The possible damage is colour coded in the table below the map according to the Modified Mercalli Intensity Scale. The red polygon represents the area of possible rupture in the model with the star representing the epicentre. (Geological Survey of Canada)

The Geological Survey Canada model for an 6.3 magnitude earthquake southwest of Terrace. The possible damage is colour coded in the table below the map according to the Modified Mercalli Intensity Scale. The red polygon represents the area of possible rupture in the model with the star representing the epicentre. (Geological Survey of Canada)

On May 11, 1973, a magnitude 4.7 shallow earthquake took place about 20 kilometers south west of Terrace, on the south side of the Skeena roughly across from the Shames mountain area. The earthquake was felt up to 120 kilometers away. The report says “The event has not been associated with any geologic features in the area and little is known about its rupture process.” The model estimated the results of a larger earthquake 6.3 magnitude in the same area. The model showed there would be strong to very strong shaking in Terrace, light to moderate shaking in Kitimat and light damage elsewhere in the BC North Coast. Most of the damage would be concentrated in a 20 kilometer zone around the epicentre.

Motivation for study

It was not just potential industrial development that motivated the new studies. The discovery of that possible fault line in the lower Douglas Channel was also a factor. Studies between 2007 and 2009 revealed there were two large submarine slides on Hawkesbury Island during the mid-Holocene sometime between 5,000 and 10,000 years ago 

The cause of the two failures is still unknown but the report says “their proximity to a nearby unmapped fault-like structure suggests that the slides could have been triggered by strong ground shaking from rupture along this structure.”

Another factor was the two well-known landslides occurred in the 1970’s in the Kitimat Arm which generated tsunamis but fortunately they occurred at low tide which decreased the impact. On October 17, 1974 a submarine slide generated a 2.8 metre tsunami. The following year on April 27, 1975, a slope failure on the northeast side of Kitimat Arm (which overlapped the 1974 failure area) displaced an estimated upper limit of 26,000,000 cubic metres of material.

“Watermark observations in Kitamaat Village estimated that the tsunami generated by this slide was up to 8.2 metres high.” The report says that while the trigger of the first event is unknown; the latter event coincided with nearby construction at that time. Modelling of the 1975 slide estimates that given the right conditions the generated tsunami waves could have been as high as 11 metres.

The report also notes that numerous landslides have also been mapped by the BC Department of Forestry in an attempt to improve safety measures for forestry workers.

The report says “The culmination of these studies brings awareness to the significant natural hazards present in the fragile coastal environment of the Coast Ranges.”

Another factor is the geology of the BC coast. The granitic mountains have rugged, steep slopes dissected by an intricate fjord system and dotted with islands of lower elevation. At lower elevations the land is covered by wet, coastal hemlock forests, which could be vulnerable to ground failures whereas higher elevations are characterized by barren rock or mountain hemlock subalpine.

Table of Seismic monitoring and GPS stations in northern BC from the Geological Survey of Canada (Geological Survey of Canada)
Table of Seismic monitoring and GPS stations in northern BC from the Geological Survey of Canada (Geological Survey of Canada)

The District of Kitimat said it has “not directly studied these issues but we are aware of potential hazards.” The development department has been advised of potential issues and site concerns.

A spokesperson for Terrace mayor Carol Leclerc told Northwest Coast Energy News in an e-mail. “I have reviewed it and distributed it to the relevant department heads. We are aware that historically Terrace has been at risk for experiencing seismic activity due to its location.”

The District of Kitimat did cooperate with National Resources in finding a location for their recently installed seismic equipment.

At Harley Bay, Gitga’at First Nation CEO Ellen Torng said the Gitga’at have been “ working with NRCan on their research in the Douglas Channel and in Hawksbury. NRC has been meeting with First Nations along the coast and have conducted community sessions on their research.

“We hosted one community session here in Hartley Bay and have regular updates from their technical team when they are in the area,” Torng said.

In addition, the District of Kitimat told Northwest Coast Energy News that Community Planning & Development department also provided local land information to geoscientists in the years leading up an international study called Batholiths on land in 2009.

Batholiths are large zones of molten rock that have solidified in the earth’s crust and are believed to play a key role in the formation and growth of continents. The Coast Mountain Range has a large concentration of batholiths, which means Kitimat was an excellent place to study the earth’s crust.

The project, which involved more than 50 scientists from nine Canadian and American universities, was set up to examine how mountain belts form and change over time and why continental mountain ranges are made of granite not basalt. Seismic imaging of the crust and mantle below the mountains required deploying thousands of seismic sensors and recorders, and recorded responses to several man-made detonations. Field work was completed in July 2009, and several scientific papers and dissertations have followed.

The Heiltsuk Nation was unable to respond to a request for comment due to the ongoing crisis from the sinking of the tug Nathan E. Stewart and the resulting spill of diesel fuel and other contaminants near Bella Bella.

Related Commentary: The earthshaking difference between Enbridge and LNG

Download the Geological Survey Studies (PDF)

Baseline Assessment of Seismic Hazards in British Columbia’s North Coast 2016

North Coast Geohazards 2016 Seismology Update

Modified Mercalli Intensity Scale

(from US Geological Survey )

Intensity Shaking Description/Damage
I Not felt Not felt except by a very few under especially favorable conditions.
II Weak Felt only by a few persons at rest,especially on upper floors of buildings.
III Weak Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.
IV Light Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
V Moderate Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.
VI Strong Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.
VII Very strong Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.
VIII Severe Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.
IX Violent Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.
X Extreme Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent.

BC issues new radio protocols for northwest forest service roads

British Columbia says it is implementing new radio protocols for forest service roads in the Kitimat region that will take effect on November 2.

The news release from Ministry of Forests, Lands and Natural Resource Operations says:

New mobile radio communication protocols are being
implemented throughout B.C. to improve safety for resource road
users. The changes include new standardized road signs, radio call
protocols and a bank of standardized mobile radio channels.

The Coast Mountain Natural Resource District will be implementing new
resource road radio channels beginning Nov. 2, 2015. The district
covers over 80,000 square kilometres and includes the major centres
of Terrace, Kitimat, Prince Rupert, New Aiyansh and Stewart.

The new protocols will impact forest service roads and other road
permit roads in the area. All affected road users must have the new
channels programmed into their mobile radios before the transition
dates. Mobile radio users are advised to retain current radio
channels and frequencies until they are no longer required.

It is recommended that mobile radio users have the full bank of
standardized resource road radio channels programmed into their
radios by certified radio technicians.

New signs posted on local resource roads will advise which radio
channels to use and provide the communication protocols, including
the road name and required calling intervals. Vehicle operators using
mobile radios to communicate their location and direction of travel
must use the posted radio channels and call protocols.

All resource road users in the affected areas should exercise
additional caution during the transition period. Drivers are reminded
that forest service roads are radio-assisted, not radio-controlled,
and to drive safely according to road and weather conditions.

Local resource road safety committees have worked with the Ministry
of Forests, Lands and Natural Resource Operations and Industry Canada
to implement these changes.

Learn more about resource road radio communications protocols and
view maps online at:
www.for.gov.bc.ca/hth/engineering/Road_Radio_Project.htm

Kitimat portion of FSR radio protocal map.(Forests, Lands and Natural Resource Operations)
Kitimat portion of FSR radio protocal map.(Forests, Lands and Natural Resource Operations)

Kitimat lifts “precautionary boil water advisory”

kitimatlogoThe District of Kitimat Friday afternoon lifted the boil water advisory declared during a heavy rain storm late last Saturday. The District says system flushing may result in some discoloured water, but it is safe to drink and the water should run clear quickly.

On its website the District said:

The precautionary boil water advisory issued on Sunday, October 11 has been lifted.

This advisory was issued by the District of Kitimat, with advice from Northern Health, after the extremely high flood levels in the Kitimat River caused an increase in turbidity in the municipal water supply. It has now been lifted after two consecutive sets of samples confirmed there was no total coliform or E.coli contamination in the potable water.

Chlorination was increased and maintained over the boil water advisory period and municipal crews flushed the water system to speed up removal of the turbid (cloudy) water. The flushing itself could result in some discoloration of the water but it is safe to drink without boiling. If your water is discoloured, let your cold water run until it clears.

The District of Kitimat apologizes for any concern or inconvenience this precautionary measure may have caused.

 

 

 

Kitimat boil water advisory could last until the end of the week, District says it depends on river levels, rain

kitimatlogoThe District of Kitimat in an update on the boil water advisory says it could last until the end of the week. There is no immediate problem because the water is still being treated.

Kitimat Chief Administrative Officer Warren Waycheshen says the turbidity from the high water means that it is not possible to do a full sample on the safety of the water.   There are no delays due to the holiday weekend, the labs are open and ready, Waycheshen told Northwest Coast Energy News.

There  are no immediate dangers to Kitimat from the high water,  he said.

The District says:

October 11, 2015
The boil water advisory issued by the District of Kitimat will remain in place at this time. Until further notice, continue to boil water for 2 solid minutes before using it for cooking or drinking.

The District of Kitimat, with advice from Northern Health, will not consider terminating the advisory until two samples conclude there is not a health risk. Sampling is not expected to be complete until at least the end of the week of October 12, 2015 and could be longer if the rain continues.

The District is treating the water as usual. There is nothing to suggest contamination is occurring; however, as a precautionary measure please continue to boil water prior to use.

Turbidity in this case means high levels of particulate matter in the river, including sand and possibly salts.  Waycheshen said the Kitimat River rose four metres on Saturday, then dropped by about two metres overnight but with the later Sunday afternoon rain the river is rising once again.

The Environment Canada forecast issued at 4 pm Sunday, calls for rain for the next week.

Wind Warning continues

The Environment Canada wind warning for the north coast was continued this morning but there are currently no alerts in effect for Kitimat.

Wind warning in effect for:

North Coast – coastal sections
The third and final disturbance in this series of storms is moving onto the northern BC Coast. The front will cross the central coast tonight. Southeast winds up to 110 km/h will develop over Haida Gwaii near noon then spread to the North Coast – Coastal Sections and Central Coast – Coastal Sections this afternoon. Winds will shift to southwest with the passage of the front then diminish this evening.

Damage to buildings, such as to roof shingles and windows, may occur. High winds may toss loose objects or cause tree branches to break.

Wind warnings are issued when there is a significant risk of damaging winds.

Radley Park

Waycheshen says there probably has been some flood damage to Radley Park, but at this point  District staff are unable to get into the area to assess the damage.

District of Kitimat issues boil water advisory; Environment Canada wind warning

kitimatlogo

The District of Kitimat has issued a boil water advisory.

Late Saturday evening, the District issued this statement on their website

Due to the significant rainfall, water entering the District of Kitimat’s system is turbid.  The District is still treating water, however, until further notice, boil water for 2 solid minutes before using it for cooking or drinking.

The District of Kitimat is working with Northern Health on this matter.

Wind warning in effect

As well Environment Canada has issued a wind warning for the north coast

North Coast – coastal sections
The third and final disturbance in this series of storms will approach the North and Central Coasts on Sunday. An intense low is forecast to track west of Haida Gwaii as moves northward. Southeast winds up to 100 km/h will develop over Haida Gwaii midday Sunday and then spread to the North Coast – Coast Sections and Central Coast – Coastal Sections in the afternoon. Winds will diminish Sunday evening as the low moves away from the region.

High winds may toss loose objects or cause tree branches to break.

Wind warnings are issued when there is a significant risk of damaging winds

The Environment Canada web page says Kitimat received 24 mm of rain in the 24 hours preceeding the forecast at 2039 on Saturday.

Sunday’s forecast calls for

Showers. Amount 10 to 20 mm. Windy this evening and after midnight. Low 8.
Sun, 11 Oct Showers. Amount 5 to 10 mm. Wind becoming south 40 to 60 km/h late in the morning. High 10.
Night Showers. Amount 20 mm. Wind south 40 to 60 km/h becoming light near midnight. Low 8.

“Very low levels” of Exxon Valdez oil threaten salmon and herring survival 25 years later

“Very low levels” of crude oil from the 1989 Exxon Valdez spill in Prince William Sound, Alaska, are a threat to the survival of herring and pink salmon that spawn in the region, according to a study released today by the US National Oceanic and Atmospheric Administration.

The study shows that embryonic salmon and herring exposed to very low levels of crude oil can develop hidden heart defects that compromise their later survival.

That means that the Exxon Valdez spill on March 24, 1989 may have had much greater impacts on spawning fish than previously recognized, according to the study published in  Nature’s online journal  Scientific Reports Very low embyronic crude oil exposures cause lasting defects in salmon and herring.

“These juvenile fish on the outside look completely normal, but their hearts are not functioning properly and that translates directly into reduced swimming ability and reduced survival,” said John Incardona, a research toxicologist at NOAA Fisheries’ Northwest Fisheries Science Center (NWFSC) in Seattle. “In terms of impacts to shore-spawning fish, the oil spill likely had a much bigger footprint than anyone realized.”

This is a juvenile pink salmon exposed to low levels of crude oil as an embryo. While these fish appear outwardly normal, they nevertheless developed heart defects that compromised their ability to swim. Fish that are less able to forage and avoid predators are much less likely to survive to adulthood. (NOAA)
This is a juvenile pink salmon exposed to low levels of crude oil as an embryo. While these fish appear outwardly normal, they nevertheless developed heart defects that compromised their ability to swim. Fish that are less able to forage and avoid predators are much less likely to survive to adulthood. (NOAA)

Previous research has shown that crude oil disrupts the contraction of the fish heart muscle cells. Embryonic fish exposed to trace levels of crude oil grow into juveniles with abnormal hearts and reduced cardiorespiratory function.

“With this very early impact on the heart, you end up with an animal that just can’t pump blood through its body as well, which means it can’t swim as well to capture food, form schools, or migrate,” said Mark Carls, toxicologist at the Alaska Fisheries Science Center. “Crude oil is changing basic physiology, or what makes a fish a fish.”

The research builds on earlier work by the Auke Bay Laboratories, part of NOAA Fisheries’ Alaska Fisheries Science Center, which found much reduced survival of pink salmon exposed as embryos to polycyclic aromatic hydrocarbons (PAH) from crude oil.

“Our findings are changing the picture in terms of assessing the risk and the potential impacts of oil spills,” said Nat Scholz, leader of the NWFSC’s ecotoxicology program and a coauthor of the new study. “We now know the developing fish heart is exquisitely sensitive to crude oil toxicity, and that subtle changes in heart formation can have delayed but important consequences for first-year survival, which in turn determines the long-term abundance of wild fish populations.”

The Exxon Valdez aground on Bligh Reef in Prince William Sound in May 1989. (NOAA)
The Exxon Valdez aground on Bligh Reef in Prince William Sound in March 1989. (NOAA)

The Exxon Valdez spill was the largest in U.S. history, with extensive oiling of shoreline spawning habitats for Pacific herring and pink salmon, the two most important commercial fish species in Prince William Sound.

Herring larvae sampled in proximity to oil were visibly abnormal, and mortality rates were higher for pink salmon embryos at oil spill sites than unaffected regions.

The herring fishery collapsed three to four years after the spill, when the herring spawned in oiled areas reached reproductive maturity.

The paper notes that the contribution of the spill to the herring population collapse, if any, was never determined and remains controversial.

Other studies, however, tend to confirm the findings, including heart problems for fish exposed to the Gulf of Mexico Deepwater Horizon spill and even fish exposed to naturally occurring oil seeps.

Oil spill caused unexpected lethal impact on herring, study shows

Gulf oil spill caused heart defects in fish embryos new study finds

The new findings suggest that the delayed effects of the spill may have been important contributors to the declines.

 This image shows transient embryonic exposures to crude oil cause lasting reductions in the swimming speed of salmon and herring, months after additional juvenile growth in clean seawater. (NOAA)

This image shows transient embryonic exposures to crude oil cause lasting reductions in the swimming speed of salmon and herring, months after additional juvenile growth in clean seawater. (NOAA)

Scientists from the Northwest Fisheries Science Center and Alaska Fisheries Science Center temporarily exposed embryonic salmon and herring to low levels of crude oil from the North Slope of Alaska and found that both absorbed chemicals at similar concentrations in their tissues. The embryos were then transferred to clean seawater and raised as juvenile fish for seven to eight months.

Few of the exposed embryos were outwardly abnormal in any way. However, closer examination of the fish revealed subtle defects that could reduce their long-term survival.

Juvenile salmon exposed to oil grew more slowly, with those exposed to the highest concentrations growing the slowest. For salmon, early survival in the ocean is strongly influenced by juvenile growth, with smaller fish suffering higher loss to predators.

Scientists used swimming speed as a measure of cardiorespiratory performance and found that fish exposed to the highest concentrations of oil swam the slowest. Slower swimming is an indication of reduced aerobic capacity and cardiac output, and likely makes fish easier targets for predators.

Exposure to oil as embryos altered the structural development of the hearts of juvenile fish, potentially reducing their fitness and swimming ability. Poor swimming and cardiac fitness is also a factor in disease resistance.

Earlier studies on the ecosystem-scale crash of the Prince William Sound herring population  several years after the Exxon Valdez spill were based on higher levels of exposure to the oil. The new study shows that that cardiac injury occurs in normal-appearing fish that survive even lower level exposures.

The scientists reviewed data on measured oil concentrations in surface water samples collected in Prince William Sound after the oil spill and during the 1989 herring spawning season. Most of the 233 samples contained less oil than was believed to be toxic to herring at the time, based on visible gross developmental abnormalities. However, nearly all of the samples contained oil at or above concentrations shown in the new study to alter heart development.

If the Exxon Valdez spill impacted heart development among a large majority of fish that were spawned in proximity to oiled shorelines, the subsequent losses of juveniles to delayed mortality would have left fewer adults to join the population. Although not direct proof, this provides a plausible explanation for the collapse of the Prince William Sound herring stock four years later, when fish spawned during the oil spill would have matured.

The study concludes that the impacts of the Exxon Valdez spill on near shore spawning populations of fish are likely to have been considerably underestimated in terms of both the geographic extent of affected habitat and the lingering toxicity of low levels of oil. The findings will likely contribute to more accurate assessments of the impacts of future oil spills, Incardona said. “Now we have a much better idea of what we should be looking for,” he said.

That means, according to the study “that the impacts of the Exxon Valdez oil spill on populations of near shore spawning fish are likely to have been considerably underestimated, in term of both the geographic extent of affected habitats and the lingering toxicity of low levels of residual oil.”

The report calls for more studies of the sensitivity of the developing fish heart since the vulnerability “also has implications for other pollution sources in marine ecosystems, including increasing maritime vessel traffic and expanding land-based urban runoff.”

In 2013, the Northern Gateway Joint Review panel said this about the Exxon Valdez  oil spill.

Scientific studies after the Exxon Valdez spill indicated that the vast majority of species recovered following the spill and that functioning ecosystems, similar to those existing pre-spill, were established.

Species for which recovery is not fully apparent, such as Pacific herring, killer whales, and pigeon guillemots, appear to have been affected by other environmental factors or human influences not associated with the oil spill. Insufficient pre-spill baseline data on these species contributed to difficulties in determining the extent of spill effects.

Based on the evidence, the Panel finds that natural recovery of the aquatic environment after an oil spill is likely to be the primary recovery mechanism, particularly for marine spills. Both freshwater and marine ecosystem recovery is further mitigated where cleanup is possible, effective, and beneficial to the environment.

Natural processes that degrade oil would begin immediately following a spill. Although residual oil could remain buried in sediments for years, the Panel finds that toxicity associated with that oil would decline over time and would not cause widespread, long-term impacts.

Related

25th anniversary of Exxon Valdez disaster looms over Northern Gateway dispute

Kitimat’s unknown role in the First World War

Ninety-seven years ago, long before the townsite was founded in the 1950s,  Kitimat was to play a short, now forgotten and unlucky role in the First World War with the launch of a vessel in New Westminster called the  War Kitimat as one of the many emergency new ships commissioned by the British government to replace vessels lost to Germany’s unrestricted submarine warfare that was sinking convoys taking vital supplies across the Atlantic.

(Note: The ship may not have been the Valley’s only role in the First World War. I have been told by Haisla members that it is believed that a couple of men from the Haisla Nation may have served in the armed forces during WWI. However, no one I have contacted, so far, has been able to confirm that information. If anyone can confirm, this story will be updated).

During the First World War, over nine million gross tons of British ships were lost due to enemy action, both submarines and surface raiders. The worst losses came in the three months ending June 1917 when over 1.4 million gross tons were sunk.

In December, 1916, the Prime Minister David  Lloyd George’s British Government appointed a “shipping controller” to manage a worldwide shipbuilding program to replace the lost vessels, to be built quickly, efficiently and to a series of standard designs. Although the vessels were often different, they were called “standard ships.” It was the Great War’s equivalent of the Liberty Ships built during the Second World War.

Many of the orders were placed with Canadian companies, others with the Japanese shipyards and British owned or controlled shipyards in Hong Kong and Shanghai. Canada created or contracted 19 emergency shipbuilders which built 137 cargo ships and 15 trawler/minesweepers. Some of these yards were purpose-built, others were repair yards that were converted to construction yards; seven were in BC, nine were in Ontario and Quebec, and three were in the Maritimes.

Orders were also placed with shipyards in the United States, but when the Americans entered the war in 1917, those ships were requisitioned by the U.S. Government.

All the ships’ names were given the prefix “War” no matter where they were built in the world.

The Canadians built both steel hulled and wooden hulled cargo vessels, including the War Kitimat, as well as yachts and sailing yachts (which likely became the war time “trawlers”). The British built 12 different types of “dry cargo” vessels, five types of “coasters” plus tankers.  The United States also built wooden hulled cargo vessels (slightly larger than the Canadian versions) and various types of steel hull cargo ships.

The government of France also contracted Canadian shipyards for its own vessel building program.

In Canada, the BC Marine Railway Company was one of the prime contractors, and the job of building four ships was awarded to the New Westminster Shipbuilding & Engineering on Poplar Island, which can be seen today from New West’s Esplanade at Westminster Quay.

The First Nations of the area had used the island for generations and in 1871 the island was designated an Indian Reserve. During the small pox epidemic of 1889, with many members of the Vancouver area First Nations struck down by the disease, a hospital was built on the island. It is believed that many of those who died of smallpox were buried there. Because of the association with disease and death the island was abandoned until 1917, when the war time necessity meant a shipyard was built on the island.

The War Kitimat under construction in New Westminster (Canadian War Museum)
The War Kitimat under construction in New Westminster (Canadian War Museum)

New Westminster Shipbuilding had the job of constructing four “war” class wooden hulled freighters, 2300 gross tonnes, 3300 dead weight tonnes, 250 feet long with a beam of 43.5 feet, with 322 nominal horse power triple reciprocating steam engines powered by two water tube boilers, turning a single screw capable of ten knots.

The company built four ships, the War Comox, War Edensaw, War Kitimat and War Ewen. The War Comox was first launched in April, 1918, but completion was held up as the shipyard waited for equipment from suppliers. That led to pressure to build, launch and complete the War Edensaw, which was launched in June 1918, and the War Kitimat, which was launched on  Sunday, August 18, 1918.

The War Kitimat immediately ran into trouble. According to the Times Colonist, right after launch the War Kitimat ran aground off New Westminster and had to be lifted off the Fraser  river bed by using jacks until was raised enough so that tugs could attach lines and tow it to deep water.  About a week later, the War Kitimat was  towed to Victoria for repairs and further fitting out (possibly to the Foundation Company shipyard which was also building five of the war class vessels. Foundation is now Seaspan’s Point Hope Marine)

The War Kitimat did make at least one voyage to Great Britain, but by the time it arrived, the war was coming to a close. After the Armistice on November 11, 1918, the ships were no longer needed and the British government sold most of them to shipping companies. (All the ships were UK registry, not Canadian)

Flag for Lloyd Belge line
Flag for Lloyd  RoyalBelge line

In 1919, the War Kitimat was sold to the Lloyd Royal Belge S.A. line of Antwerp, Belgium and renamed the Serbier.

On January 12, 1920, the Serbier, on a  voyage from Cartagena and Oran to Antwerp with zinc ore and general cargo on board, sprang a leak in her engine room during a “raging gale” in the Bay of Biscay and sank  80 nautical miles (150 km) off Penmarc’h, Finistère, France at 47°38′N 6°10′W. Her Capt. A. Canfrère and the crew were rescued by the French ship SS Docteur Pierre Benoit.

How the ship came to be named War Kitimat isn’t certain. It was probably named after the Kitimat River since other vessels in the War category were named Skeena, Stikine, Babine, Niagara, Ottawa (others were named for cities like Halifax or Toronto).

The Belgian shipping company did not give up on the name Serbier. It purchased another US-built War cargo ship, first named the War Hound by the British. After the US entered WWI in 1917 and took over the building there it became the Lake Huron, a US Navy Transportation Service mine carrier. From later in 1920, Royal Belge operated the new Serbier until 1924, when it passed through French, Norwegian, Danish and then as the Advance,  Finnish ownership. The Advance was seized in Panama by the United States in 1941 and renamed the Trojan. After the Second World War, the US returned the ship to Finland. It sailed as the Advance until it was sold a Greek shipping company in 1965 and scrapped at Piraeus in 1966.

Of the ships under British control, 821 ships were ordered by the UK shipping board and 416 were completed. Fourteen were lost to enemy action. The remaining orders were cancelled but often completed by the shipyards.

Many of the “war” or “standard” ships passed through various owners.

During the Second World War many played their original role and took part in the convoys that crossed the Atlantic.  Many were sunk during those crossings. Others, sold to growing Japanese shipping interests in the 1920s and 1930s, were sunk by US destroyers and submarines. Others like the War Hound /Serbier survived to the 1950s and 1960s.

Of the War Kitimat’s sister ships built in New Westminster, the War Comox was sold to an Italian company, renamed the Guidatta and scrapped at Genoa in 1925, The War Ewen was sold to a German company, renamed the Etienne Marcel and scrapped in Germany in 1925. The War Edensaw, under the original name, was carrying Admiralty stores from Constantinople to Malta,  when it caught fire on June 25, 1919 and sank 94 nautical miles east of the St. Elmo Lighthouse on Malta.

As for Poplar Island, it was zoned for industrial use but no one could come up with ideas for how to use the island.   New Westminster sold the island to Rayonier Canada in 1945, where it became an anchorage for log booms on the Fraser River. The successor company, Western Forest Products sold it back to New Westminster in 1995,  The island is still a wilderness area in the middle of urban Vancouver and subject to treaty and land claims negotiations with the area’s First Nations.

Related links
Poplar Island: A History as Thick and Colorful as the Trees

Emergency Shipbuilders of World War I

World War One Standard Built Ships

World War One Standard Built Ships (this is a different site to the one above)

Vessels Built by B.C. Marine Railway Co

The Ship’s List (database of ships, link is to Lloyd Royal Belege entry)

 

Editor’s Note:   Up until now Kitimat has not had a reason, unlike other communities, to mark Canada’s role in the First World War.  We suggest that should the District of Kitimat choose to do so either this year or in the next three years, August 18, the date of the launch of the War Kitimat might be an appropriate date, in addition to Remembrance Day on November 11.

Canadian, US Coast Guards to exercise with Alaska emergency ship towing system

The United States Coast Guard says the US and Canadian Coast Guards will “conduct a towing evolution using a State of Alaska Emergency Towing System” on Friday afternoon off Juneau, Alaska.

The participating vessels are the Canadian Coast Guard  Marine Service Vessel and  Ice Strengthened Medium Navaids Tender CCGS Bartlett and the US Coast Guard cutter USGC Maple.  Like the Barlett, the Maple is also a buoy tender.

CCGS Barlett (Canadian Coast Guard)
CCGS Barlett (Canadian Coast Guard)

In 2014, when the Russian vessel Simushir was adrift off Haida Gwaii, the towing system on the Canadian Coast Guard’s Gordon Reid was inadequate and the line snapped.  A commercial tug was hired to take the Simushir into port at Prince Rupert.   As Northwest Coast Energy News reported in October, 2014, the US Coast Guard deployed the Alaska Towing System to Haida Gwaii but it wasn’t used at that time despite a record of success by the US Coast Guard in towing vessels off Alaska waters.

Related:

When the Simushir was adrift,  Alaska was ready, BC and Canada were not

On the Simushir, Oceans Minister Shea takes ministerial responsibility to a new low, the bottom of the sea

 

 

 

 

Dilbit dangerous to young fish, laboratory study shows

Diluted bitumen, also known as dilbit, a mixture of oil sands bitumen and natural gas dilutants can seriously harm fish populations, according to research study at Queen’s University and the Royal Military College of Canada published this week.

At toxic concentrations, effects of dilbit on exposed fish included deformities and clear signs of genetic and physiological stress at hatch, plus abnormal or uninflated swim bladders, an internal gas-filled organ that allows fish to control their buoyancy. Exposure to dilbit reduces their rate of survival by impairing their ability to feed and to avoid predators.

Post-doctoral fellow Barry Madison works with the fish in Valerie Langlois' lab. (Queen's University)
Post-doctoral fellow Barry Madison works with the fish in Valerie Langlois’ lab. (Queen’s University)

Among the other findings from the study were

    • Embryo toxicity of dilbit was comparable to that of conventional oils.
    • Developmental malformations increased with increasing dilbit concentrations.
    • Chemical dispersion broadened the genotoxic effects of dilbit

“This new study provides a clearer perspective on the potential risks to Canada’s aquatic resources of dilbit spills, and a technical basis for decisions on dilbit transportation within Canada,” says Peter Hodson Environment Studies, Biology at Queens. “It reduces some of the uncertainty and unknowns about the hazards of dilbit.”

This study characterized the toxicity and physiological effects of unweathered diluted bitumen (Access Western Blend dilbit; AWB) to a fish used for laboratory studies. Embryos of Japanese medaka (Oryzias latipes) were exposed for 17 days to dilutions of dilbit physically-dispersed by water and chemically-dispersed by dispersants

AWB dilbit exposure was not lethal to medaka, but resulted in a high prevalence of blue sac disease (BSD), impaired development, and abnormal or un-inflated swim bladders. Blue sac is a disease of young trout and other salmonid species; usually caused by unsuitable hatchery water. It turns the yolk sac bluish and is thought to be caused by a lack of oxygen.

The research was funded by Fisheries and Oceans Canada’s National Contaminants Advisory Group and the next stage will determine whether fish species native to Canada will be affected by dilbit exposure. The work also includes the development of genetic markers of exposure to dilbit and toxicity that could be used to assess whether wild fish that survive a spill are still affected.

The research team includes Dr. Valérie Langlois (Environmental Studies, Royal Military College of Canada) and Dr. Barry Madison (Royal Military College of Canada).

Dr. Hodson is also a member of a Queen’s research team tasked to determine whether dilbit spilled into rivers would contaminate bed sediments, specifically areas where fish such as salmon, trout, chars, whitefish and graylings spawn, to the extent that the survival of their embryos would be affected.

The research was published in ScienceDirect and is one of the first studies of dilbit on young fish.

The finding could be significant because both the proposed Northern Gateway pipeline and the proposed Kinder Morgan expansion will cross areas near spawning streams.

“Devastating megathrust earthquake” a “substantial hazard” for Haida Gwaii, Canada-US study warns

A “devastating megathrust earthquake” could hit Haida Gwaii sometime in the future, according to Canadian and US studies carried out after the magnitude 7.8 earthquake off Haida Gwaii on Oct. 27, 2012 and the 7.5 magnitude quake off Craig, Alaska, a few weeks later on Jan. 5, 2013.

The 2004 Indian Ocean earthquake and the 2011 Tōhoku earthquake in Japan, both accompanied by major tsunamis are recent examples of “great” (higher than magnitude 8.0) megathrust earthquakes. Most of the concern on the west coast has been the likelihood of a megathrust earthquake on the Cascadia Fault on the Juan de Fuca plate that stretches from northern California to the middle of Vancouver Island.

New Douglas Channel geological studies near completion

Is Kitimat ready for a “big one?”

The 2012 Haida Gwaii main shock was the second largest seismic event in Canada since the establishment of a modern seismograph network. The first was the 1949 Haida Gwaii/Queen Charlotte earthquake with a magnitude of 8.1 That 1949 Haida Gwaii earthquake was a strike-slip event, where the plates move side-to-side, similar to the 1906 San Francisco earthquake and other quakes on the San Andreas Fault in California.

The 2012 Haida Gwaii earthquake is characterized in the studies as a “mini-megathrust” event, where part of the crust is pushed upward, meaning that a larger megathrust could have much more destructive consequences from both the earthquake and a possible tsunami.

A diagram of the situation  off Haida Gwaii that triggered the October 2012 "mini megathrust" earthquake seen at the lower centre, while the 1949 slip strike   earthquake is seen at the top. (Bulletin of the Seismological Society of America)
A diagram of the situation off Haida Gwaii that triggered the October 2012 “mini megathrust” earthquake seen at the lower centre, while the 1949 slip strike earthquake is seen at the top. (Bulletin of the Seismological Society of America)

Complex system of faults

The new studies show that the Pacific and North America plate boundary off the coast of British Columbia and southeastern Alaska creates a system of faults capable of producing very large earthquakes. The scientists conclude that while the two earthquakes in 2012 and 2013 released strain built up over years on the tectonic plates, those events did not release strain along the Queen Charlotte Fault off the west coast of Haida Gwaii. That means the fault remains the likely source of a future large earthquake.

Map showing the pattern of earthquakes along the Queen Charlotte Fairweather Fault system and the location of the Queen Charlotte Terrace.  (Bulletin of the Seismological Society of America)
Map showing the pattern of earthquakes along the Queen Charlotte Fairweather Fault system and the location of the Queen Charlotte Terrace. (Bulletin of the Seismological Society of America)

A special issue of the Bulletin of the Seismological Society of America (BSSA), released Monday, April 6, 2015, contains 19 scientific and technical papers, outlining the results of the work carried out over the past two years.

The team estimated the rupture dimension of the 2012 Haida Gwaii earthquake to be about 120 kilometres long at a depth of about 30 kilometres.

The Craig earthquake ruptured the Queen Charlotte fault over a distance of more than 100 kilometres and at a depth of about 20 kilometres.

The two areas are joined in what is called the Queen Charlotte Fairweather Fault System. To the south the Queen Charlotte Fault also interacts with the Juan de Fuca plate that stretches from Vancouver Island to northern California.

“The study of these two quakes revealed rich details about the interaction between the Pacific and North America Plates, advancing our understanding of the seismic hazard for the region,” said Thomas James, research scientist at Geological Survey of Canada.

Two faults off Haida Gwaii

The studies conclude that the interaction between the plates off Haida Gwaii is much more complex than previously believed. Before the 2012 earthquake, the Queen Charlotte Fault, a strike-slip fault similar to the San Andreas Fault in California, was believed to be the dominating tectonic structure in the area. The 2012 tremor confirmed the existence of a previously suspected thrust fault beneath what is called the “Queen Charlotte Terrace,” to the west of the Queen Charlotte Fault, where the Pacific plate is sliding at a low angle below the North American plate.

The Queen Charlotte Terrace, which is about a kilometre below the surface of the ocean, is built up of layers of sediment, several kilometres thick, scraped off the oceanic plate as it subducts under the North American plate. It may also include some fragments of oceanic crust. For most of the terrace, it is “present as a clearly defined linear feature,” but the study adds: “north of about 53.5° N, a complex pattern of ridges and valleys appears.”

The earthquake was “essentially a mini-megathrust earthquake along the dipping plate interface of a subduction system,” one of the scientific papers says. The epicenter of the Haida Gwaii main shock was located about five kilometres landward (northeast) of the Queen Charlotte Fault. That probably means that the rupture was near the bottom of the locked plates, where the plate motion’s side to side movement is also thrusting downward. Significant aftershocks appeared to cluster on the periphery of the main rupture zone with most of the aftershocks occurring seaward to the west.

The scientists used GPS observations of crustal motion to locate the earthquake’s rupture offshore to the west of Haida Gwaii.

The situation off Haida Gwaii is complex because while the Pacific plate is converging with the North American plate at a rate of 15 to 20 millimetres a year, at the same time the two plates are slipping by each other toward the north northwest at angle of about 20 degrees at a rate of about 50 millimetres a year.

Honn Kao, a seismologist with the Geological Survey of Canada said, “This was an event the thrust interface of the plate boundary system, confirming that there is a subduction system in the Haida Gwaii area.

“The implication of a confirmed subduction zone is that in addition to the Queen Charlotte Fault, we now have another source which can produce devastating megathrust earthquakes in the area,” said Kao.

The study of the Haida Gwaii tremor looked at the causative faults, the rupture processes and depths of the main shock and sequence of strong aftershocks.

The Haida Gwaii earthquake generated a significant tsunami that left deposits indicating run-up exceeding 3 metres (maximum 13 metres) in a number of bays and inlets along about 230 kilometres along the west coast of Haida Gwaii. In Hawaii, a 0.8 metre wave was measured on a tide gauge.

In Queen Charlotte City perceptible shaking lasted for one and half to two minutes, with very strong shaking for about 30 seconds. The earthquake was felt as far away as Yukon Territory, Alberta, and Montana.

The study says “Damage was limited, in part owing to the sparse population, but also because of the seismic resistance of the generally low rise, wood-frame buildings on the islands. Felt intensities were at expected values close to the source zone, but regional intensities were smaller than predicted.”

The Haida Gwaii rupture also shook southeastern Alaska. The northwest direction of ground motion then may have influenced the timing of the Craig earthquake a few weeks later in January 2013. That earthquake occurred farther north in southeast Alaska, where relative plate motion is nearly parallel to the Queen Charlotte fault.

Aftershocks
.

Map showing the pattern of aftershocks following the October 2012 Haida Gwaii earthquake. (Bulletin of the Seismological Society of America)
Map showing the pattern of aftershocks following the October 2012 Haida Gwaii earthquake. (Bulletin of the Seismological Society of America)

The Haida Gwaii aftershocks clustered around the periphery of the rupture zone, both on the seaward and landward side of the plate boundary and reflected what the study calls “normal faulting behavior–caused by the bending, extending or stretching of rock– rather than the thrust faulting of the main shock.” The pattern of aftershocks is similar to those observed after the 2011 Japanese megathrust earthquake.

“Our observations of normal faulting imply that the main shock of the Haida Gwaii earthquake dramatically altered the stress field in the rupture zone, especially in a neighboring region,” Kao said.

The distribution of aftershocks occurred to the north of a previously identified seismic gap where large earthquakes have not occurred in historic times. The gap is located to the south of the where 1949 magnitude 8.1 Queen Charlotte earthquake ruptured.

Though the Haida Gwaii earthquake may have activated some part of the Queen Charlotte Fault, Kao said, it was limited and did not relieve stress along the seismic gap.

The study concludes:

The Haida Gwaii event confirmed substantial seismic and tsunami hazard from large thrust events on the plate margin along the southern Queen Charlotte fault. It occurred where relatively young oceanic lithosphere under thrusts North America and in some ways is an analog for the much larger megathrust earthquakes known to occur on the Cascadia subduction zone to the south, where the young Juan de Fuca plate and other small plates subduct beneath North America. The Haida Gwaii earthquake had a complex pattern of main shock rupture and aftershocks and a large tsunami.

Further study needed

The Geological Survey of Canada plans further studies to understand the formations off Haida Gwaii.
One question to ask is if there are any records of major earthquake events in the past history of Haida Gwaii. The study notes that the impact of the tsunami was relatively minor “in this region with steep rocky coastlines.” That means there are limited sources of coastal sediments that can be checked for past events. It adds: “Low-elevation lakes, ponds, and bogs may offer the best opportunities for paleotsunami studies” warning that large earthquakes in the past that produced tsunamis may have left little evidence in the “paleoseismic record of Haida Gwaii and similar settings worldwide.”

 

 


Megathrust

Megathrust earthquakes occur at subduction zones at destructive plate boundaries where one tectonic plate is subducted (forced underneath) by another. These interplate earthquakes are the planet’s most powerful, with moment magnitudes that can exceed 9.0. Since 1900, all earthquakes of magnitude 9.0 or greater have been megathrust earthquakes. During the rupture, one side of the fault is pushed upwards relative to the other, and it is this type of movement that is known as thrust. The displacement of the ocean in a thrust can trigger a tsunami.

Transform fault
A transform fault is one where the motion is predominantly horizontal. Those faults end abruptly and are connected on both ends to other faults, ridges, or subduction zones. The best-known (and most destructive) are those on land at the margins of tectonic plates. Transform faults are the only type of strike-slip faults at plate boundaries show strike-slip or side-to-side in movement.

Queen Charlotte Terrace
The Queen Charlotte Terrace is a 25 kilometre wide zone of built up marine sediment immediately west of the active Queen Charlotte fault. The crust is about 12 kilometres thick at the terrace. On Haida Gwaii, the earth’s crust is 18 kilometres thick at the eastern edge. On the BC mainland the crust is in excess of 30 kilometres thick.

Historic earthquakes.
The 1949 Haida Gwaii quake was one of the largest in the recorded history of North America.

The largest known earthquake along the coast was the megathrust event on the Cascadia fault on January 26, 1700 where the Juan de Fuca plate ruptured for about 1,000 kilometres along from what is now northern California to Vancouver Island, estimated at magnitude 9.0. The dating is based on a tsunami that hit Japan that had no associated local earthquake as well studies of tree rings from the remains of trees downed in the tsunami.


Related links
Kitimat to issue tsunami hazard and evacuation map

Afterearthquake Kitimat must immediately upgrade emergency communications

The earthshaking difference between Enbridge and LNG

DFO study on ancient Douglas Chanel tsunamis show minimal impact on Kitimat, devastation at Hartley Bay

Geological Survey of Canada identifies tsunami hazard, possible fault line on Douglas Channel

Scientists identify major Japanses style tsunami hazard for west coast