2012 Haida Gwaii earthquake

2012 Haida Gwaii earthquake
Date October 27, 2012 (2012-10-27)
Origin time 8:04:08 p.m. (PDT) [1]
Duration 90 seconds [2]
Magnitude 7.8 Mw
Depth 17.5 km (10.9 mi)
Epicenter 52°46′08″N 131°55′37″W / 52.769°N 131.927°W / 52.769; -131.927Coordinates: 52°46′08″N 131°55′37″W / 52.769°N 131.927°W / 52.769; -131.927
Type Thrust [2]
Areas affected Canada
Max. intensity V (Moderate) [1]
Peak acceleration .2g [2]
Tsunami Yes
Casualties None

The 2012 Haida Gwaii earthquake occurred just after 8:04 p.m. PDT on October 27. The shock had a moment magnitude of 7.8 and a maximum Mercalli Intensity of V (Moderate). The earthquake's epicentre was on Moresby Island of the Haida Gwaii archipelago (formerly known as the Queen Charlotte Islands). This was the second largest Canadian earthquake ever recorded by a seismometer, after the 1949 Queen Charlotte Islands earthquake, about 135 kilometres (84 mi) away.[3]

Earthquake

Strong shaking was felt throughout Haida Gwaii where residents in Masset, Skidegate, Sandspit, and Queen Charlotte City were evacuated to higher ground.[4] Minor shaking was felt in Prince Rupert and in other cities of the Interior such as Prince George, Quesnel, and as far away as Kamloops.[5] Electricity service was interrupted in Bella Coola.[6]

USGS ShakeMap for the event

Although the earthquake occurred on the Queen Charlotte Fault, a primarily strike-slip boundary between the Pacific and North American plates where the Pacific Plate moves approximately north-northwest with respect to the North America plate at a rate of about 50 mm/yr.,[1] the 2012 quake exhibited a thrust mechanism, more characteristic of the Cascadia Subduction Zone to the south.[7]

Tsunami

A tsunami warning was issued for the North American Coast from the Alaskan Panhandle to Vancouver Island, but later limited to the North Coast region of British Columbia. Canadian authorities were questioned for issuing a tsunami warning nearly 40 minutes after the U.S. had issued their warning.[8] The greatest wave heights recorded at tide gages in Canada were 0.25m (9.8 in.) at Langara Island and 0.22m (8.7 in.) at Winter Harbour.[9] In Tofino on Vancouver Island, the tsunami warning sirens were activated and residents in low-lying areas evacuated their homes.[6] The maximum wave height recorded in Tofino was 0.09m (3.5 in.).[9] Tofino's tsunami warning system was activated after communication with the provincial coordinating centre was cut off.[10]

In the U.S., Hawaii was also placed on alert, and over 100,000[11] people were evacuated to higher ground. The maximum wave height recorded at tide gages in Hawaii was 0.79m (31 in).[9] Other warnings were issued for the states of Oregon and California, but were subsequently lifted.[12]

Damage

Despite the earthquake's large magnitude, no major structural damage was reported from any of the population centres in the vicinity.[13] This can be explained by the remoteness of the tremor's epicentre. No casualties or major injuries were recorded from the quake, likely due to the sparsely populated nature of the region.[8] As a result of the earthquake and its aftershocks, the famed hot springs in Gwaii Haanas National Park on Hotspring Island dried up.[14]

Aftershocks

There were 94 aftershocks of magnitude 4.0 or greater lasting until November 7, as recorded by the USGS.

The largest of these numerous aftershocks was a 6.3 magnitude earthquake that occurred 56 kilometres (35 mi) to the west of the main tremor on the morning of October 28.[15] This was followed on October 29 by a 6.2 aftershock 50 kilometres (31 mi) to the south of the original quake.[16]

References

  1. 1 2 3 USGS. "M7.8 - Haida Gwaii, Canada". United States Geological Survey.
  2. 1 2 3 Bird, A. L.; Lamontagne, M. (2015), "Impacts of the October 2012 Magnitude 7.8 Earthquake near Haida Gwaii, Canada", Bulletin of the Seismological Society of America (Seismological Society of America) 105 (2B): 1178, 1180
  3. ↑ "Canada Earthquake: British Columbia Hit, Tsunami Warning For Alaska, Hawaii". Huffingtonpost.com. October 28, 2012. Retrieved October 28, 2012.
  4. ↑ Justine Hunter, Ian Bailey And Wendy Stueck (October 29, 2012). "Minor temblor rattles Los Angeles after strong quake off B.C. coast". Toronto: The Globe and Mail. Retrieved October 28, 2012.
  5. ↑ CBC News (October 27, 2012). "Tsunami heads for Hawaii after huge B.C. quake". CBC. Retrieved October 28, 2012.
  6. 1 2 "Magnitude 7.8 Quake Strikes Off Western Canada". The New York Times. The Associated Press. October 28, 2012. Retrieved October 28, 2012.
  7. ↑ "Superquakes, supercycles, and global earthquake clustering", Chris Goldfinger, Yasutaka Ikeda and Robert S. Yeats, EARTH, January 7, 2013.
  8. 1 2 Oct 29, 2012 7:32 AM PT (October 30, 2012). "B.C. tsunami warning came 39 minutes after U.S. alert - British Columbia - CBC News". Cbc.ca. Retrieved November 9, 2012.
  9. 1 2 3 "West Coast and Alaska Tsunami Information". Oldwcatwc.arh.noaa.gov. Retrieved November 9, 2012.
  10. ↑ DEREK SPALDING, timescolonist.com October 28, 2012 (October 28, 2012). "B.C. to review emergency response in wake of Haida Gwaii quake, communication problem with Tofino". Timescolonist.com. Retrieved November 9, 2012.
  11. ↑ "As it happened: Hawaiian tsunami alert - ABC News (Australian Broadcasting Corporation)". Abc.net.au. Retrieved November 9, 2012.
  12. ↑ "– ''Tsunami messages issued in the past 7 days''". Tsunami.gov. Retrieved November 9, 2012.
  13. ↑ "Aftershocks continue to hit Haida Gwaii, 6.3 magnitude occurs right before noon". The Northern View. October 28, 2012. Retrieved November 9, 2012.
  14. ↑ McKnight, Zoe (November 2, 2012). "Earthquake empties famed Haida Gwaii hot springs (with video)". Timescolonist.com. Retrieved November 9, 2012.
  15. ↑ "M6.3 - 177km SSW of Masset, Canada 2012-10-28 18:54:16 UTC". Earthquake.usgs.gov. Retrieved November 9, 2012.
  16. ↑ Oct 29, 2012 8:20 PM PT (October 30, 2012). "Another earthquake rattles B.C. coast - British Columbia - CBC News". Cbc.ca. Retrieved November 9, 2012.

External links

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