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Intertidal biological indicators of coseismic subsidence during the Mw 7.8 Haida Gwaii, Canada, earthquake

Peter J. Haeussler, Robert C. Witter and Kelin Wang
Intertidal biological indicators of coseismic subsidence during the Mw 7.8 Haida Gwaii, Canada, earthquake (in 2012 Haida Gwaii and 2013 Craig earthquakes at the Pacific North America plate boundary (British Columbia and Alaska), Thomas S. James (editor), John F. Cassidy (editor), Garry C. Rogers (editor) and Peter J. Haeussler (editor))
Bulletin of the Seismological Society of America (May 2015) 105 (2B): 1265-1279

Abstract

The 28 October 2012 M (sub w) 7.8 Haida Gwaii earthquake was a megathrust earthquake along the very obliquely convergent Queen Charlotte margin of British Columbia, Canada. Coseismic deformation is not well constrained by geodesy, with only six Global Positioning System (GPS) sites and two tide gauge stations within 250 km of the rupture area. To better constrain vertical coseismic deformation, we measured the upper growth limits of two sessile intertidal organisms, which are controlled by physical conditions, relative to sea level at 25 sites 5 months after the earthquake. We measured the positions of rockweed (Fucus distichus, 617 observations) and the common acorn barnacle (Balanus balanoides, 686 observations). The study focused on the western side of the islands where rupture models indicated that the greatest amount of vertical displacement, but we also investigated sites well away from the inferred rupture area to provide a control on the upper limit of the organisms unaffected by vertical displacement. We also made 322 measurements of sea level to relate the growth limits to a tidal datum using the TPXO7.2 tidal model, rather than ellipsoid heights determined by GPS. Three methods of examining the data all indicate 0.4-0.6 m subsidence along the western coast of Moresby Island as a result of the 28 October 2012 Haida Gwaii earthquake. Our data are, within the errors, consistent with data from two campaign GPS sites along the west coast of Haida Gwaii and with rupture models that indicate megathrust rupture offshore, but not beneath, the islands.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 105
Serial Issue: 2B
Title: Intertidal biological indicators of coseismic subsidence during the Mw 7.8 Haida Gwaii, Canada, earthquake
Title: 2012 Haida Gwaii and 2013 Craig earthquakes at the Pacific North America plate boundary (British Columbia and Alaska)
Author(s): Haeussler, Peter J.Witter, Robert C.Wang, Kelin
Author(s): James, Thomas S.editor
Author(s): Cassidy, John F.editor
Author(s): Rogers, Garry C.editor
Author(s): Haeussler, Peter J.editor
Affiliation: U. S. Geological Survey, Anchorage, AK, United States
Affiliation: Geological Survey of Canada, Pacific Geoscience Centre, Natural Resources Canada,, Sidney, BC, Canada
Pages: 1265-1279
Published: 201505
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 42
Accession Number: 2015-085135
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch maps
N52°00'00" - N54°15'00", W133°10'00" - W131°00'00"
Secondary Affiliation: U. S. Geological Survey, USA, United StatesGeological Survey of Canada, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201536
Program Name: USGSOPNon-USGS publications with USGS authors
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