Ocean Networks Canada - cascadia

From Cosmos to Core: Wiring the Abyss Expedition 2018

kshoemak@uvic.ca — Wed, 12 Sep 2018 21:33:51 +0000

The deep sea holds answers to many scientific questions about the origin of life on Earth, our changing ocean, and even outer space. This year, Ocean Networks Canada’s (ONC) annual Wiring the Abyss expedition expanded infrastructure to monitor both deep sea and deep space⎯from the cosmos to the core⎯reaching new milestones for our offshore observatory in the northeast Pacific Ocean.

ONC’s annual maintenance expeditions allow for instrumentation to be added, maintained, and recovered, live streaming these deep sea operations in real time so everyone can #knowtheocean. Wiring the Abyss Leg 1, aboard Canadian Coast Guard ship John P. Tully, deployed instruments and new infrastructure using the heavy lift capability of the ROPOS remotely operated vehicle (ROV). During Leg 2, the exploration vessel (E/V) Nautilus completed the final positioning and installation of Leg 1 elements, and deployed more instruments. Over 27 days at sea, the team powered on, deployed, maintained or recovered 270 devices during 30 dives (Figure 1).

Figure 1. Canadian Coast Guard Ship (CCGS) John P. Tully (left) and E/V Nautilus (right).

Expansion of instruments: highlights

The successful completion of Wiring the Abyss 2018 included many new and exciting expansion achievements for ONC and for Canada.

To help us understand the cosmos, a neutrino experiment was deployed at Cascadia, our deepest site, to test the transmission properties of the water. The two specialized instrument arrays will evaluate the location for potential detection of neutrinos––subatomic particles that when studied can provide insight into the origin and evolution of the universe. These instruments were developed by a team at the Technical University of Munich in Germany––the same team that developed the IceCube South Pole Observatory––who watched the deployment of their instruments live from Germany (Figure 2). The collection of detailed measurements over two years will assess the deep-sea site for future use. Read more about this exciting neutrino experiment here.

Figure 2. The neutrino test site consists of a pair of 100-metre-long test strings that mimic what happens when a neutrino passes by. The team watched live as the experiment was deployed at a depth of 2,700 metres at ONC’s Cascadia observatory.

ONC completed the installation of the final offshore seismometers for British Columbia’s earthquake early warning system. Over the last three summers, ONC has installed a total of eight strong-motion sensors along the Cascadia subduction zone at Cascadia Basin, Clayoquot Slope, and Barkley Canyon. Two kinds of Canadian-built sensors were used—a Nanometrics Titan accelerometer (Figure 3) and an RBR tiltmeter. Using two different types of sensors provides a level of sophistication that adds redundancy and allows for improved signal comparison. The proximity of these offshore sensors to a possible megathrust earthquake could provide additional crucial seconds of warning. ONC will also be installing 26 sensors on land by March 2019, when ONC delivers the system to Emergency Management BC.

Figure 3. ROV Hercules carefully submerges an accelerometer inside the buried green caisson at Barkley Canyon, the final installation of ONC’s offshore earthquake early warning sensor system.

Wiring the Abyss 2018 successfully doubled the instrumentation at Endeavour Hydrothermal Vent Field, Canada’s first marine protected area and the world’s most international deep-sea cabled observatory site. Instruments from Canada, United States, United Kingdom, France, and China are now connected to ONC’s data management portal, Oceans 2.0. At the Main Endeavour Field, a string of three cabled Guralp Maris ocean bottom seismometers were added to a dense network of instruments to monitor seismic activity at this spreading mid-ocean ridge (Figure 4). A hydrophone was installed close to active venting activity, and three benthic resistivity sensors were added at Mothra, Main Endeavour and Main Endeavour South to monitor hot hydrothermal fluid and chloride concentration flowing from the vents. Media Factsheet on international sensors at Endeavour hot vents

Figure 4. A string of three cabled short-period seismometers were deployed at Endeavour, in a water depth of 2,200 metres. The Guralp team—who designed and manufactured the instruments—watched live from their England office.

Good news for the water column community. After three years, the refurbished vertical profiling system was reinstalled at Barkley Canyon upper slope and is collecting data once again.
Other maintenance tasks included relocating instruments, cleaning camera lenses, checking on or recovering devices and experiments, and repairing instruments showing irregularities in data––such as CORK 1027C, which needed a valve position changed to ensure that the correct pressure was recorded.

Using robots to observe marine life

In addition to conducting deep sea maintenance tasks and manoeuvres, ROVs are also equipped with high-resolution cameras that make it possible to conduct video surveys to study the biodiversity and abundance of both water column (gelatinous plankton and fish) and the seafloor (fish and invertebrate) benthic communities. ONC scientists onboard assisted the ROV pilots to regulate speed, height from the seafloor, and video camera settings to capture the marine life at the highest resolution possible. ONC has gathered 11 years of ROV video and data that are essential for understanding deep-sea biodiversity in the northeast Pacific (Figure 5).

Figure 5. A curious salmon shark was spotted swimming near the surface during an ROV dive ascent from Cascadia Basin.

New cameras at Mothra, Barkley Canyon mid-east, upper slope and axis are now connected and streaming. These cameras turn on at intervals throughout the day to visually monitor experiments, instruments, and the diverse marine life. Watch for yourself on our Sights and Sounds live video page.

Sampling the deep sea

During the expedition, onboard scientists collected over 80 samples from the deep sea, including sediment, benthic megafauna, water, hydrothermal vent fluid, and methane gas hydrate bubbles. Push core samples were taken at nearly every dive conducted at Endeavour, Barkley Canyon, Clayoquot Slope and Cascadia Basin (Figure 6), to support a variety of research projects, including the documentation of the region’s little-known benthic infauna (organisms living in the sediment).

Figure 6. Onboard EV Nautilus, the expedition team processes a push core sample taken at Cascadia Basin.

As part of a new collaboration with scientists from the Natural History Museum of London, benthic megafauna samples––organisms over one centimetre that inhabit the sediment-water interface––were collected at the Endeavour vent sites. Samples of other invertebrates––such as polychaete worms, crustaceans, corals (Figure 7), sea anemones, and brittle stars––were also collected for proper taxonomical identifications in an ongoing partnership with the Royal BC Museum.

Figure 7. A rock sample with resident corals and sponges collected at Clayoquot Slope Bullseye.

Methane hydrate seeps, gas, and fluid samples were taken at Endeavour hydrothermal vent field and at Barkley Canyon using a 'gas-tight’ bottle held over the hot fluids or cold methane bubble streams (Figure 8). These samples are key for determining the biogeochemical nature of the vent fluids and measuring the rates and amount of the methane emanating from the seafloor.

Figure 8. Sampling super-heated hydrothermal vent fluid using a gas-tight bottle.

Mapping the seafloor

The expedition took advantage of E/V Nautilus state-of-the-art multibeam echo-sounding equipment by mapping the ocean floor in areas of interest (Figure 9). Two surveys––between Endeavour and Clayoquot Slope and northwest of Barkley Canyon––mapped the lower portion of the continental slope around the subduction zone deformation front. These new maps will be valuable for determining future seafloor changes caused by the next Cascadia megathrust earthquake.

Figure 9. This image from E/V Nautilus’ Seafloor Information System shows the multibeam echo-sounding survey of an area between Clayoquot Slope and Barkley Canyon. The geographic (top) and water column (bottom) mapping fills gaps in existing high-resolution bathymetry along the continental slope to increase our understanding of the area.

Preparation leads to success

“Wiring the Abyss 2018 represented one of the most complex expeditions that ONC has completed. The sheer number of new instruments, platforms, and supporting infrastructure required months of preparations, focused work from ONC teams, multiple ships and ROVs and well planned and executed installations,” comments Adrian Round, ONC’s executive director of observatory operations.

Despite the challenge of working over two kilometres beneath the waves in one of the harshest environments on Earth, ONC is proud that our collective efforts achieved over 90 percent of its Wiring the Abyss Expedition 2018 goals.

Relive our expedition excitement on our video archive SeaTube, or find out what’s happening on the ocean floor right now via Oceans 2.0, where data from all of our cabled instruments can be viewed in real time.

Canadian scientist awarded for exceptional contribution to Earth science!

linzhill@uvic.ca — Tue, 23 Aug 2016 21:22:25 +0000

Congratulations to Dr. Kelin Wang for being elected a Fellow of the American Geophysical Union (AGU), an international organization dedicated to advancing Earth and space sciences for the benefit of humanity. Becoming a fellow of AGU is an honour provided to only 0.1% of AGU’s 62,000 plus members from over 140 countries.

Kelin and his students are studying the geodynamics of subduction zones, especially processes related to the generation of large earthquakes and tsunamis around the world. His models for earthquakes inform building codes, risk assessments, and tsunami preparedness along the Pacific coast of North America. This work is relevant to the tsunami research being done at Ocean Networks Canada (ONC).

Dr. Kelin Wang, senior scientist with Natural Resources Canada and adjunct professor at the University of Victoria

ONC recently collaborated with Kelin and his student, Dawei Gao, whose research on rupture scenarios along the Cascasdia fault, together with ONC’s work on Digital Elevation Models, will provide the necessary pieces to develop tsunami inundation maps and tools for preparedness for British Columbia coastal communities.

ONC’s tsunami research will continue to advance with instrument development and more detailed propagation models in collaboration with world-class scientists and organizations such as IBM Canada, the Natural Sciences and Engineering Research Council’s Collaborative Research and Development Grant, Fisheries and Oceans Canada, Emergency Management BC, Alberni-Clayoquot Regional District, NOAA, and GeoBC.

Kelin Wang is a senior scientist with Natural Resources Canada and adjunct professor at the University of Victoria who has published more than 200 publications and nearly 10,000 citations.

Some of his recent publications linked to ONC include:

Nykolaishen, L., H. Dragert, K. Wang, T. S. James, and M. Schmidt (2015), GPS Observations of Crustal Deformation Associated with the 2012 Mw 7.8 Haida Gwaii Earthquake, Bull Seismol Soc Am, 0120140177–, doi:10.1785/0120140177.

Obana, K., M. Scherwath, Y. Yamamoto, S. Kodaira, K. Wang, G. Spence, M. Riedel, and H. Kao (2015), Earthquake Activity in Northern Cascadia Subduction Zone Off Vancouver Island Revealed by Ocean-Bottom Seismograph Observations, Bull Seismol Soc Am, 0120140095–, doi:10.1785/0120140095.

Insua, T. L. et al. (2015), Advancing Tsunami Detection: The Ocean Networks Canada Tsunami Project, in 11th Canadian Conference on Earthquake Engineering, Canadian Association for Earthquake Engineering, Victoria.

Insua, T. L. et al. (2015), Preliminary tsunami hazard assessment in British Columbia, Canada, in Fall Meeting, AGU, American Geophysical Union, San Francisco.

Gao, D., K. Wang, M. Riedel, T. Sun, T. L. Insua, C. Goldfinger, and G. R. Priest (2015), On the Possibility of Slip-to-trench Rupture in Cascadia Megathrust Earthquakes, in Fall Meeting, AGU, American Geophysical Union, San Francisco.

Award-winning study compares the Cascadia subduction zone to offshore Japan

vkeast@uvic.ca — Sun, 28 Feb 2016 18:34:38 +0000

In January 2016, University of Victoria Master’s student, Dawei Gao, won an Outstanding Student Poster Award at the 2015 American Geophysical Union Fall meeting. His co-authored paper on earthquake dynamics explores the question: What would happen if the Cascadia subduction fault (off the west coast of Canada) ruptured, or broke, in the same way as the 2011 Tohoku earthquake?

Dawei Gao stands ready to answer questions beside his award-winning student poster at the 2015 Fall Meeting of the American Geophysical Union.

Dawei developed profiles of the Cascadia subduction zone and compared them with those offshore Japan. His award-winning paper demonstrates various rupture scenarios along the Cascadia fault, and uses this knowledge to demonstrate tsunami wave propagation.

Given the complex structure at the leading edge or trench of Cascadia’s fault line, Dawei shows that the slip-to-trench rupture that occurred in Japan is not very likely to happen on North America’s west coast. “But for tsunami hazard assessment, we should still consider all of the scenarios, including the slip-to-trench rupture,” says Dawei.

“The incoming tectonic plate at Cascadia is blanketed by approximately three kilometres of sediment near the deformation front. This is in sharp contrast to the sediment-starved Japan trench where one continuous fault extends all the way to the trench, a configuration that facilitates slip-to-trench rupture.“

Dawei’s work is a vital piece in the development of a comprehensive earthquake and tsunami early warning and response system for the west coast. With funding from Emergency Management BC (March 2015), Ocean Network Canada’s tsunami project is using 75 of Dawei’s simulated tsunami models to help produce earthquake-generated tsunami inundation maps, showing the amount of flooding expected at different areas along the coast.

That information will help people living along the coast respond quickly to future megathrust earthquakes and the tsunamis that follow.

Dawei Gao, Kelin Wang, Michael Riedel, Tianhaozhe Sun, Tania Lado Insua, Chris Goldfinger, and George R. Priest (2015), On the possibility of slip-to-trench rupture in Cascadia megathrust earthquakes, presented at 2015 AGU Fall meeting, San Francisco, California.

Congratulations Dawei! We’ll be following your progress and look forward to working with you in the future.

For more information about research in plate tectonics and earthquake dynamics at Ocean Networks Canada, please contact: Martin Heeseman, staff scientist.

Introduction to Clayoquot Slope

cbonnett@uvic.ca — Thu, 15 Aug 2013 19:49:38 +0000

Clayoquot Slope at a Glance

Region: On the mid-continental slope off south-central Vancouver Island, roughly 20 km landward of the toe of the Cascadia subduction zone.
Number of Instrument Platforms: 1
Depth: 1258 m
Location: Lat: 48°40.2387’ N, Lon: 126°50.8832’ W
Seafloor Composition: Soft muddy sediments 3-5 km thick, along with gas hydrate deposits.
Principal Research: Gas hydrates, seafloor fluids and gases, Cascadia margin, earthquakes, deep-sea organisms.

Environment/Ecosystems

The Clayoquot Slope is a zone where sediment accumulates in an accretionary subduction setting. The sediments of the subducting Juan de Fuca tectonic plate are scraped off and accreted to the North American plate as the plates converge.

As sediments thicken and compact from accretion, pore waters and gases are expelled from the sediment, forming cold-water vents such as the Bullseye Vent, as well as gas hydrate deposits and gas seeps.

Ocean Networks Canada’s Clayoquot Slope site is home to a variety of deep-sea organisms, and recent dives have observed a number of demersal fish – which feed along the seafloor – such as rockfish, flatfish, thorny heads, and rattails (image below), along with echinoderms, molluscs, arthropods, cnidarians, and the bacterial mats found around methane hydrates.

What Makes Clayoquot Slope Unique?

Clayquot Slope is located in the region of the highest predicted rate of fluid escape from compacting the sediments of the accretionary wedge. The released fluids contain methane that forms hydrates in the top few hundred metres of the sediments, and they have a strong influence on the biology, geology, and potentially even climate.

A series of scientific drill holes exist in this area (the oldest one called ODP 889 which added a historic name to this site), and 2 of which are filled with strings of instruments extending a few hundred metres into the sediment. These instruments are currently recording automonously but both may potentially be connected to the NEPTUNE observatory to stream live data.

The region around Clayoquot Slope exhibits the highest density of seeps with regular activity of gas venting into the water column. One area, dubbed 'Bubbly Gulch', is closely monitored using a sonar, and nearby sensors are measuring tidal pressure, temperature, currents, ground shaking (seismic activity), and even hydrogeological conditions within the sediments. This instrument suite affords a unique opportunity to study trigger mechanisms for natural venting and vent bursts. Escaping gas bubbles rise through the water column with a thin coating of hydrate surrounding the gas, heading toward the atmosphere where they could act as a powerful greenhouse gas, though they have not been observed to rise above depth less than approximately 500 m below the sea surface in this region.

To monitor the physical dynamics of the gas hydrates associated with the Bullseye cold vent, there is a Controlled Source Electromagnetic (CSEM) experiment, the world's first to be connected to an ocean observatory, currently (2013) recovered for maintenance, and a SeaFloor Compliance (SFC) apparatus with the world's first gravimeter to stream live data from the ocean floor, though the latter is slated for relocation to our Endeavour site on the Juan de Fuca ridge.

Since the Cascadia margin is subject to regular giant megathrust earthquakes (with a 300-500 year recurrence rate), close observations of the stress regime with hydrogeological pressure monitoring in the boreholes will provide a unique opportunity to detect any changes associated with these subduction events.

Principal Research

Research at Ocean Networks Canada’s Clayoquot Slope revolves largely around the presence of gas hydrate deposits and the proximity of seafloor boreholes, which were drilled by the Integrated Ocean Drilling Program (IODP) in collaboration with Ocean Netowrks Canada. Used mainly for studies on seafloor dynamics, research findings have helped illuminate the parameters surrounding the large “megathrust” earthquakes which tend to occur every 300-500 years along the Cascadia subduction zone.

Selected Ongoing research at Clayoquot Slope

Bullseye Vent Gas Hydrates, a project initiated by Nigel Edwards and Ele Willoughby and continued by Marion Jegen utilized 2 stationary imaging experiments Controlled Source Electromagnetic (CSEM), and Sea Floor Compliance (SFC), to monitor the physical dynamics of the gas hydrates associated with the Bullseye cold vent at Clayoquot Slope.
Bubbly Gulch sonar investigation, established by George Spence and Michae Riedel, monitors methane gas release from the seafloor into the water column from backscatter data.
The Seismograph Network, led by Garry Rogers, uses four broadband/strong motion seismographs and four short period seismographs to study subsea earthquakes and other tectonic activity.
Led by Kelin Wang, Earl Davis, and Kate Moran, the Ocean Crustal Hydrogeology project utilizes boreholes drilled across the Juan de Fuca tectonic plate to help reveal the relationship between dynamic processes such as episodic plate motion, internal plate strain, and earthquakes.
A future expansion, piloted by Jeff McGuire and John Collins, will install geodymanic tools (tilt-meter and precision depth recorders) that capture the deformation of the seafloor in response to tectonic forces.

VIDEO Clips

Octopus broods inside debris at Clayoquot Slope (ODP 889)

Deploying the Controlled-source Electromagnetic Experiment

Methane bubbles from the seafloor at ONC’s Clayoquot Slope

An introduction to ONC’s northeast Pacific observatories

Cascadia Subduction Zone

dwowens@uvic.ca — Mon, 15 Oct 2012 07:00:00 +0000

A subduction zone (Bebout et al., 1996) is an area where two plates are converging, with one plate moving beneath the other. As the down-going (subducting) plate moves deeper, it transports water into depth where it is heated and released. The heat from the mantle and core causes the surrounding rocks to melt and become fresh magma for volcanic eruptions. The down-going plate is recycled in the Earth’s mantle. At the Cascadia subduction zone the ocean crust of the Juan de Fuca plate is subducting beneath the continental crust of the North American plate. At subduction zones, there usually is an area where the two plates become locked. This means that they are not slipping past each other and frictional stress can build up, storing large amounts of energy. When this stress finally reaches a breaking point, it releases the energy that has been stored resulting in what is known as a “megathrust” earthquake.

The locked zones can hold for hundreds of years as the Cascadia subduction zone has done since 26 January 1700 when the last megathrust earthquake occurred in this area (Satake et al., 2003). The earthquake magnitude was estimated as 9.0 and it resulted in a tsunami that was recorded in Japan. Evidence of this earthquake can be confirmed by geological evidence (land level changes, tsunami traces, turbidite deposits), biological evidence (tree rings), and human records (Native American stories and Japanese records) (Satake et al., 1996; Satake et al., 2003; Satake and Atwater, 2007). Megathrust earthquakes tend to occur in this region approximately every 300-500 years.

References

Bebout, E., Scholl, W., Kirby, H., & Platt, P. (1996). Subduction top to bottom. Geophysics Monograph Series, 96, 384. doi:10.1029/GM096

Satake, K., & Atwater, B. F. (2007). Long-term perspectives on giant earthquakes and tsunamis at subduction zones. Annual Review of Earth and Planetary Sciences, 35(1), pp. 349-374. doi:10.1146/annurev. earth.35.031306.140302

Satake, K., Shimazaki, K., Tsuji, Y., & Ueda, K. (1996). Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700. Nature, 379, pp. 246-250.

Satake, K., Wang, K., & Atwater, B. F. (2003). Fault slip and seismic moment of the 1700 Cascadia earthquake inferred from Japanese tsunami descriptions. Journal of Geophysical Research, 108(B11), pp. 1-17. doi:10.1029/2003JB002521

Hydrate Growth at Bullseye Vent?

rlat@uvic.ca — Fri, 09 Dec 2011 08:00:00 +0000

Gas hydrates are ice-like solids composed of natural gas, usually methane in marine environments, and water. Hydrates are known to exist in the Cascadia margin, west of Vancouver Island, beneath the seafloor. Sediment stiffness is increased by frozen hydrates, like ice in winter mud. The degree of stiffness is an indicator of the amount of hydrate present per unit volume. Gas hydrate outcrops, venting and topography in the Cascadia margin have been intensively studied and are observed to change over time. Does the volume of hydrates also change with time? University of Toronto researchers Lisa Roach and Nigel Edwards are trying to find out.

An uncommon, specialized exploration technique, known as seafloor compliance is used to probe beneath the seafloor, by examining the deflection of the seafloor caused by waves on the ocean surface. Waves on the surface create pressure changes on the seafloor; as they “push” the seafloor down, it deflects them. The amount of seafloor deflection depends on the stiffness of the sediment, which, in turn, depends on hydrate content. In areas where there are fewer buried hydrates, the seafloor is more compliant (less stiff). The depth at which hydrates are buried beneath the seafloor can be inferred from gravity wave frequency at the seafloor. A compliance value in the higher frequency range describes shallower hydrates, while lower frequencies describe deeper deposits.

Roach and Edwards are using this technique to study changes in buried gas hydrates in a place called Bullseye Vent at our Clayoquot Slope location (depth 1260m). To determine the change in compliance, pressure and velocity data were recorded at 1 second intervals for a total of 228 24-hour long records between 1 October 2010 and 16 May 2011. Pressure was measured with a differential pressure gauge (DPG), capable of recording pressure changes of 1Pa in a background of 1MPa, while very small velocities, associated with seafloor wave deflections as small as the radius of an iron atom, are measured by a broadband ocean-bottom seismometer (OBS). These instruments are part of the NEPTUNE Canada ODP 889 seismic station.

A trend in the compliance over the 228 days was revealed (shown above). The trend represents a -2.88% change in the compliance of the sediments over the study period. This decrease in the compliance corresponds to an increase in the stiffness in sediments (indicating an increase of gas hydrate amount) between 0-600mbsf (metres below seafloor). Hydrates are stable within the top 225m of sediments, so a change in compliance could have been caused by property changes over this depth range. To match the decrease in compliance to the increase in hydrate content, the stiffness of the layer between 0-100mbsf (initial hydrate content of 22%) was varied until the -2.88% change was observed following a model suggested by the IODP drilling. A rather surprising three fold increase in hydrate concentration of the 100m layer, from 22% to 64% is predicted.

Assuming a 100m diameter hydrate mass, the change in hydrate concentration is equivalent to a change in hydrate mass of 600 million kg, which poses the question where does this mass come from? If this decrease is distributed over the entire hydrate zone (~250mbsf) the change in hydrate concentration and mass would be smaller. Maybe the zone of increased stiffness extends to greater depths and is in a layer associated with a hydrate production mechanism?

As more high-resolution data are collected in the future, scientists will gain increased understanding of how fluctuations in compliance relate to the dynamics of the hydrate system and its evolution. There is still much to be learned!

Ocean Networks Canada - cascadia

From Cosmos to Core: Wiring the Abyss Expedition 2018

Expansion of instruments: highlights

Using robots to observe marine life

Sampling the deep sea

Mapping the seafloor

Preparation leads to success

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Canadian scientist awarded for exceptional contribution to Earth science!

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Award-winning study compares the Cascadia subduction zone to offshore Japan

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Introduction to Clayoquot Slope

Clayoquot Slope at a Glance

Environment/Ecosystems

What Makes Clayoquot Slope Unique?

Principal Research

Selected Ongoing research at Clayoquot Slope

VIDEO Clips

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Cascadia Subduction Zone

References

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Hydrate Growth at Bullseye Vent?

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