2013-07-25 faults in the lower mainland and burnaby · pdf filefaults in the lower mainland...

Faults in the Lower Mainland and Burnaby Mountain

Limitations

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• This presentation provides a summary of the letter report issued to Kinder Morgan Canada dated March 7, 2013 titled “Faults in the Lower Mainland and Burnaby Mountain”.

• The intent of the report, and thus for this presentation is to provide a summary on some of the relevant studies that have been conducted over the last 90 years. Neither the report nor this presentation should be used as conclusive evidence for the presence or absence of faults or landslides in the area. Further studies are warranted and neither the report nor this presentation should be considered as a detailed engineering assessment.

• For further details, this audience is referred to the letter report.

Outline

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1. Regional Tectonic Setting2. Known Active Faults3. Quaternary Faults in Southwestern B.C.4. Historical Interpretations of Faults and Landslides

around Burnaby Mountain5. Recent Satellite Imagery6. Challenges in Lower Mainland Fault Studies7. Conclusions and Path Forward

Regional Tectonic Setting

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• The Cascadia subduction zone lies along the west coast of North America

• The Juan de Fuca plate is thrust beneath the continental plate, resulting in compression of western Washington and southwestern B.C against the Coast Mountains buttress.

• Compression is accommodated by faults and folds in Washington and B.C.

Image modified from: Wells, R.E., Weaver, C.S., and Blakely, R.J. 1998. Forarc migration in Cascadia and its neotectonic significance. Geology, vol. 26, pp. 759-76

Known Active Faults

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• An ‘active’ fault is typically defined as one that has ruptured (moved) during the Holocene Epoch - the last 11,000 years.

• ‘Potentially Active’ faults typically last ruptured during the much longer Quaternary Period - up to 1.6 million years ago.

• Recently, Holocene fault activity has been identified in Washington by the USGS.

Fault data courtesy of the U.S. Geological Survey

Faults and Features in SW B.C. and NW Washington

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© BGC Engineering Inc. 2013

Discontinuities in the Lower Mainland

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• Although many Quaternary faults in the U.S. have been well documented, there is very little information available on Quaternary faults in southwestern BC.

• However, since the 1920s, and perhaps earlier, geological investigations have identified discontinuities between adjacent soil or rock units.

• Historically, both faulting and landslide activity have been proposed as possible explanations for the discontinuities.

Specific Features in the Lower Mainland

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• Since 1923, multiple discontinuities in the Lower Mainland have been identified:– Johnston/GSC, 1923– Webster, 1958– Roddick/GSC, 1965– Blunden, 1971– Blunden, 1975– Crampton, 1980s– Armstrong, 1990– Turner et al., 1998


Johnston, 1923

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• In 1923, a study by Johnston illustrated what was indicated as an east-to-west trending fault within Burrard Inlet, 1.5 km north of Burnaby Mountain.

• The fault was not actually observed, but used to explain an unconformity between sedimentary and intrusive rocks exposed on the north and south sides of Burrard Inlet.

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Johnston, W.A. 1923. Geology of the Fraser River Map Area. Geological Survey of Canada, Memoir 135, 87 p. with map. © Department of Natural Resources Canada. All rights reserved.

Webster, 1958

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• In 1958, as part of a report for the B.C Department of Highways, Webster interpreted the north slope of Burnaby Mountain as a slide in Tertiary bedrock.

• Tension cracks described at the slide crown, and problems with buildings and infrastructure were interpreted as evidence for landslide movement. These included:– Difficulty maintaining grade and alignment of a steel water main, a

road surface and a Canadian Pacific Railway track.– Shell Oil Company abandoning plans for a large installation due to

unstable soil conditions.– TransMountain Pipelines relocating the site of the future Westridge

Terminal to the west after studying the area. • Webster’s report concluded that excess pore water pressure was

triggering slope movement. There was no mention of faulting.

Geological Survey of Canada, 1965

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• In 1965, Roddick, on behalf of the Geological Survey of Canada produced a map depicting an ‘approximate’ fault trending east to west across Burnaby Mountain.

• The trace of the feature is coincident with the landslide scarp identified by Webster from 1958.

• The 1923 fault in Burrard Inlet drawn by Johnston was not shown.

Roddick, J.A. 1965. Vancouver north, Coquitlam and Pitt Lake map areas, British Columbia, with special emphasis on the evolution of the plutonic rocks. Geological Survey of Canada, Memoir 335. © Department of Natural Resources Canada. All rights reserved.

Blunden, 1971

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• In 1971, Blunden produced a report summarizing the geology of Vancouver’s ‘Downtown Coal Peninsula’

• This report identified several possible faults in Burrard Inlet, along Hastings Street and in the Lost Lagoon area based on local geological information.

• These faults have not been referenced in later publications on faulting in the region.


Blunden, 1975

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• In a subsequent report by Blunden in 1975, Blunden cites a map drawn in February 1859 by Colonel R.C. Moody showing Stanley Park as an Island.

• However, the report also includes a map drawn in June 1859, only 4 months later, by Captain G.H Richards, showing Stanley Park as a peninsula.

Blunden, R.H. 1975. Historical Geography of the Fraser River. Adventures in Earth Science Series Number 3. A Contribution of the Pacific Earth Science Methods Workshop, UBC.

Blunden, 1975 Cont’d.

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• Blunden accounted for the discrepancy between the two maps by suggesting that an earthquake may have uplifted Stanley Park between February and June.

• An earthquake large enough to cause this much uplift would likely have been noted in the historical record, however, no such record has been found.


Crampton, 1980s

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• In the 1980s, Crampton, inferred several sets of faults, running both North-South and East-West.

• Four sets of faults were identified running North-South, essentially fracturing Burnaby Mountain.

• Of several sets identified running East-West, one set runs parallel to the fault identified by Roddick, however, the location of this fault is also coincident with the headscarp of the north flank slide described by Webster.

Crampton, C.B. 1980s. Natural science studies of Burnaby and Belcarra mountains. Simon Fraser University Discussion Paper No. 8.

Armstrong, 1990

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• In 1990, Armstrong produced a monograph on Vancouver geology in which described large block slides of sedimentary rocks on the steep North side of Burnaby Mountain.

• The monograph suggested that construction of the CPR and Barnett Highway at the base of the slope may have reactivated part of the slide mass.

Turner et al., 1998

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• In 1998, a group of authors produced ‘GeoMap Vancouver’, a geological map covering the Vancouver metropolitan area.

• This map showed a fault traversing the North slope of Burnaby Mountain, roughly coincident with a fault mapped by Roddick in 1965, and the location of a landslide backscarp mapped by Webster in 1958.

Turner, R.J.W., Clague, J.J., Groulx, B.J. and Journeay, J.M. 1998. GeoMap Vancouver, Geological Map of the Vancouver Metropolitan Area. Geological Survey of Canada Open File 3511. © Department of Natural Resources Canada. All rights reserved.

Recent Satellite Imagery

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• Since the 1970s, the Lower Mainland has had extensive satellite imagery coverage.

• Through both aerial photography and satellite imagery, the north flank of Burnaby Mountain shows signs of disturbance in the form of arcuateshapes located immediately downslope of Simon Fraser University.

• Based on initial interpretations, the arcuate shapes identified are interpreted to be landslide features, coincident with those indicated by Armstrong.

• The following slides illustrate the features identified as probable landslide scarps.


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Challenges in Lower Mainland Fault Studies

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• Active, shallow crustal faults are generally identified through paleoseismology or by studying fault behaviour.

• Such methods are limited in the Lower Mainland due to thick glacial and post-glacial sediments which overlie the area.

• Modern techniques, such as Light Detection And Ranging (LiDAR) or geophysics may help identify faults obscured by thick sediments.

• Active faults can also be inferred to within a few kilometres from clustered or aligned earthquake hypocentres.

© Groupe Info Consult 2013 © UNAVCO 2013© Ashley Dace 2011

Conclusions and Path Forward

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• At present, there are no known active faults in the Lower Mainland, however that does not mean there are no active faults. Recent work in the U.S. has revealed active faults within 5 km of the border, and it is possible that given comparable research active faults could be found north of the border.

• Although many researchers have invoked faults to explain geological discontinuities around Burnaby Mountain, there is not enough evidence to conclude that the faults purported to exist are real or active.

• What are KMC’s next steps: Further geological and geotechnical investigation to understand geologic

processes and hazards around Burnaby Mountain and effect on KMC facilities will be conducted as part of the detailed design phase of the TMEP

This work will include bedrock and surficial geological mapping, a compilation of historical geological and geotechnical information around the study area, the use of available surface and subsurface imaging technology such as LIght Detection and Ranging (LIDAR) and geophysics, and other techniques.

References

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Armstrong, J.E. 1990. Vancouver Geology. Edited by Charlie Roots and Chris Staargaard. Geological Association of Canada -Cordilleran Section. 128 p.

Barnett, E.A. 2007. Active faulting at the northern margin of the greater Puget lowland: A paleoseismic and magnetic-anomaly study of the Kendall fault scarp, Whatcom County, northwest Washington. Master’s thesis presented to the Faculty of Humboldt State University.

Barnett, E.A., Kelsey, H.M., Sherrod, B.L., Blakely, R.J., Hughes, J.F., Schermer, E.R., Haugerud, R.A., Weaver, C.S., and Siedlecki, E. 2006. Active faulting at the northeast margin of the greater Puget Lowland—A paleoseismic and magnetic-anomaly study of the Kendall Scarp, Whatcom County, northwest Washington. Eos, Transactions, American Geophysical Union, v. 87, Abstract S31A-0183.

Barnett, E.A., Kelsey, H.M., Sherrod, B., Blakely, R.J., Hughes, J., Schermer, E.R., Haugerud, R.A., Weaver, C., Siedlecki, E.M., and Blakely, R.J. 2007. Active faulting at the northeast margin of the greater Puget Lowland; a trenching and wetland coring study of the Kendall Fault scarp, Whatcom County, northwest Washington. Geological Society of America Abstracts with Programs, v. 39, p. 61.

Blais-Stevens, A., Rogers, G.C. and Clague, J.J. 2011. A Revised Earthquake Chronology for the last 4,000 Years Inferred from Varve-Bounded Debris-Flow Deposits beneath an Inlet near Victoria, British Columbia. Bulletin of the Seismological Society of America, vol. 101, no. 1, pp. 1-12.

Blunden, R.H. 1971. Vancouver’s downtown (coal) peninsula – urban geology: B.Sc. Thesis (Publ.), Dept. of Geology, University of British Columbia, 53 p. 22 Figures.


Bryant, W.A., and Hart, E.W. 2007. Fault-rupture hazard zones in California—Alquist-Priolo Earthquake Fault Zoning Act with index to Earthquake Fault Zone maps. California Department of Conservation, California Geological Survey, Special Publication42.

References

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Crampton, C.B. 1980s. Natural science studies of Burnaby and Belcarra mountains. Simon Fraser University Discussion Paper No. 8.

Dunphy, M. December 13, 2012. Waves, plates and earthquakes on B.C.’s West Coast. Georgia Straight, p. 15.

Goldfinger, C., Nelson, C.H., and Johnson, J.E. 2003. Holocene earthquake records from the Cascadia subduction zone and northern San Andreas Fault based on precise dating of offshore turbidites. Annual Review of Earth and Planetary Sciences, vol. 31, no. 1, pp. 555-577.

Haugerud, R.A., Sherrod, B.L., Wells, R.E., Hyatt, T., 2005, Holocene displacement on the Boulder Creek Fault near Bellingham, WA and implications for kinematics of deformation of the Cascadia Forearc: Geological Society of America Abstracts with Programs, v. 37, p. 476.

Johnston, W.A. 1923. Geology of the Fraser River Map Area. Geological Survey of Canada, Memoir 135, 87 p. with map.

Kelsey, H.M., Sherrod, B.L., Blakely, R.J. and Haugerud, R.A. 2012. Holocene faulting in the Bellingham forearc basin: Upper-plate deformation at the northern end of the Cascadia subduction zone. Journal of Geophysical Research, vol. 117.

Lidke, D.J., Johnson, S.Y., McCrory, P.A., Personius, S.F., Nelson, A.R., Dart, R.L., Bradley,

Lee-Ann, Haller, K.M., and Machette, M.N. 2003. Map and data for Quaternary faults and folds in Washington State: U.S. Geological Survey Open-File Report 03-428, 15 p., 1 pl.,scale 1:750,000, http://earthquake.usgs.gov/hazards/qfaults/. Fault data updated November 3, 2010.

McCaffrey, R.A., Qamar, I., King, R.W., Wells, R., Khazaradze, G., Williams, C.A., Stevens, C.W., Vollick, J.J. and Zwick, P.C. 2007. Fault locking, block rotation and crustal deformation in the Pacific Northwest, Geophys. J. Int., vol. 169, no. 3, pp. 1315–1340.

Mulder, T.L. and Rogers, G.C. 2002. Seismicity in the vicinity of the Leech River fault. Seismological Research Letters, v. 73, no. 2, p. 240.

References

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Roddick, J.A. 1965. Vancouver north, Coquitlam and Pitt Lake map areas, British Columbia, with special emphasis on the evolution of the plutonic rocks. Geological Survey of Canada, Memoir 335.

Rogers, G. C. 1994. Earthquakes in the Vancouver area, in Geology and Geological Hazards of the Vancouver Region, Southwestern British Columbia, edited by J. W. H. Monger, GSC Bulletin 481, pp. 221-229.

Siedlecki, E.M., and Schermer, E.R. 2007. Paleoseismology of the Boulder Creek fault, Kendall, WA. Geological Society of America Abstracts with Programs, v. 39, p. 26.

Turner, R.J.W., Clague, J.J., Groulx, B.J. and Journeay, J.M. 1998. GeoMap Vancouver, Geological Map of the Vancouver Metropolitan Area. Geological Survey of Canada Open File 3511.

Webster, A.T. 1958. Report on Hastings Barnet Slide Vicinity STA. 216 and CPR Mile 120.3 Cascade Subdivision. Province of British Columbia, Department of Highways, Materials Testing, Research and Development Branch.

Wells, R.E., Weaver, C.S., and Blakely, R.J. 1998. Forarc migration in Cascadia and its neotectonic significance. Geology, vol. 26, pp. 759-763.

2013-07-25 faults in the lower mainland and burnaby · pdf filefaults in the lower mainland...

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