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TitleSeismic induced flow disruption of Gandll K'in Gwaay.yaay thermal springs, Gwaii Haanas National Park Reserve, Canada
AuthorGrasby, S E; Ferguson, G; Bartier, P; Neville, L
SourceApplied Geochemistry vol. 103, 2019 p. 118-130, https://doi.org/10.1016/j.apgeochem.2019.03.005 (Open Access)
Year2019
Alt SeriesNatural Resources Canada, Contribution Series 20180443
PublisherElsevier BV
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf; html
ProvinceBritish Columbia; Western offshore region
NTS103B/11
AreaGandll K'in Gwaay.yaay; Hotspring Island; Gwaii Haanas National Park Reserve
Lat/Long WENS-131.5000 -131.0000 52.7500 52.5000
Subjectsgeophysics; geochemistry; tectonics; geochronology; earthquakes; seismicity; epicentres; geothermal resources; thermal springs; groundwater flow; flow regimes; groundwater discharge; discharge rates; deformation; modelling; slope stability analyses; oxygen isotopes; hydrogen isotopes; groundwater geochemistry; total dissolved solids; pH patterns; geothermometry; groundwater temperatures; groundwater circulation; water table; water levels; geophysical logging; electrical properties; conductivity; radiometric dating; radiocarbon dating; carbon-14 dates; history; bedrock geology; structural features; faults; lithology; sedimentary rocks; igneous rocks; intrusive rocks; tectonic setting; Recent; Neogene; Pliocene; Miocene; Gandll K'in Gwaay.yaay geothermal system; October 28, 2012 magnitude 7.8 Haida Gwaii earthquake; Hecate Basin; Queen Charlotte Basin; Hotspring Island Formation; indigenous peoples; traditional knowledge; oral history; Phanerozoic; Cenozoic; Quaternary; Tertiary; Mesozoic; Cretaceous
Illustrationslocation maps; geoscientific sketch maps; cross-sections; aerial photographs; tables; plots; time series; schematic representations
ProgramGeothermal Energy, Geoscience for New Energy Supply (GNES)
Released2019 03 09
AbstractThe October 28, 2012 magnitude 7.8 Haida Gwaii earthquake disrupted flow of the only thermal springs in the Haida Gwaii archipelago of western Canada. Springs of the Gandll K'in Gwaay.yaay geothermal system ceased discharge at existing outlets and spring pools drained empty. Subsequent visits to the remote site documented return of flow at the lowest elevation discharge points, although at a greatly reduced discharge rate. Over time thermal water discharge was renewed at higher elevations and the total discharge rate increased. To understand better how seismic activity affected the spring flow, at a site ?30 km distant from the epicentre, a study was initiated to inform development of a conceptual model of the thermal system. Stable isotope data show that thermal waters discharging at Gandll K'in Gwaay.yaay originate in deep circulation of meteoric waters, where they are heated by the normal increase in ground temperature with depth. Geothermal gradients in the region are relatively low, and aqueous geothermometry suggests that circulation depths of the system are ?3.6 km. There is no significant difference in overall water geochemistry from before and after the earthquake, either suggesting that the flow path was clogged, or that changes in water pressure in the recharge zone have reduced the overall system drive. We propose a conceptual model, suggesting that the earthquake induced a drop in the water table of the recharge zone, reducing the driving force of the flow system, leading to flow cessation. As the water table returned back to normal elevations the spring system has begun to return to pre-earthquake discharge patterns. This interpretation is consistent with traditional knowledge of the site, were oral history records previous earthquake induced flow cessations and subsequent returns of spring flow.
Summary(Plain Language Summary, not published)
The October 28 2012 magnitude 7.8 Haida Gwaii earthquake disrupted flow of the only thermal springs in the Haida Gwaii archipelago of western Canada. Springs of the Gandll K'in Gwaay.yaay geothermal system ceased discharge at existing outlets and spring pools drained empty. This study, conducted jointly with Parks Canada, examines why flow stopped. With the aid of traditional knowledge of the Haida People, a conceptual model of the flow system predict progressive return of flow to the thermal springs.
GEOSCAN ID314549