| Title | Shear-wave velocity structure in the vicinity of the 2012 Mw 7.8 Haida Gwaii Earthquake from receiver function inversion |
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| Author | Gosselin, J M; Cassidy, J F ; Dosso, S E |
| Source | Bulletin of the Seismological Society of America vol. 105, no. 2B, 2015 p. 1-8, https://doi.org/10.1785/0120140171 |
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| Year | 2015 |
| Alt Series | Earth Sciences Sector, Contribution Series 20140151 |
| Publisher | Seismological Society of America (SSA) |
| Document | serial |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf |
| Province | Western offshore region; British Columbia |
| NTS | 102O; 103B; 103C; 103F; 103G; 103J; 103K |
| Area | Haida Gwaii; Queen Charlotte |
| Lat/Long WENS | -134.5000 -130.0000 54.5000 51.0000 |
| Subjects | geophysics; tectonics; earthquake studies; earthquakes; earthquake magnitudes; earthquake risk; earthquake mechanisms; earthquake foci; tectonic setting; aftershocks; landslides |
| Program | Public Safety Geoscience Assessing Earthquake Geohazards |
| Released | 2015 04 07 |
| Abstract | The thrust mechanism of the 2012 Mw 7.8 Haida Gwaii earthquake suggests convergence across the transpressive Pacific-North America plate boundary in the region is accommodated by underthrusting, with
important consequences for seismic- and tsunami-hazard analysis. This article investigates the crustal structure and extent of subduction beneath Haida Gwaii by nonlinear inversion of receiver function data processed from teleseismic recordings at
five land-based seismograph stations. Three of these stations were deployed since the 2012 earthquake to extend coverage to the southeast and have not been analyzed previously. The inversions provide estimates of the shear-wave velocity structure
beneath much of Moresby Island. Results indicate a positive velocity contrast at approximately 18-26 km depth, interpreted as a shallow continental Moho. A 12-17 km thick low shear-wave velocity zone is also identified, which increases in depth from
~25 to 42 km along the direction of plate convergence, which is interpreted as subducting oceanic material. These results provide the first evidence that the subducting oceanic plate extends beneath the entirety of Moresby Island. |
| Summary | (Plain Language Summary, not published)
The October 27, 2012 magnitude 7.7 earthquake resulted in up to 4 m of movement along a previously unknown fault just off the west coast of Moresby
Island, Haida Gwaii. Following that earthquake, 6 new seismic stations were deployed on Moresby Island to help monitor aftershocks activity. We utilise seismic data from those new stations to map, for the first time, the detailed earth structure
beneath Haida Gwaii. Using these new data we image the base of the continental crust at 17-29 km below Moresby Island. More importantly, we image a significant low-velocity zone that is dipping to the east beneath Moresby Island (at depths of 38-45
km). We interpret this as the Pacific Plate pushing beneath Haida Gwaii. This is critical new information for assessing ground shaking from future earthquakes. |
| GEOSCAN ID | 295071 |
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