| Title | Testing an empirical Green's function method for determining the rupture parameters of the 24 April 2014 Vancouver Island Earthquake |
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| Author | Paul, C; Cassidy, J F ; Dosso, S E; Hutchinson, J |
| Source | Bulletin of the Seismological Society of America 2020 p. 1-13, https://doi.org/10.1785/0120200233 |
| Image |  |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20190299 |
| Publisher | Seismological Society of America |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Province | British Columbia; Western offshore region |
| NTS | 92E; 92L/01; 92L/02; 92L/03; 92L/04; 102I/01; 102I/02 |
| Area | Vancouver Island; Pacific Ocean |
| Lat/Long WENS | -128.6667 -126.2500 50.0833 48.0000 |
| Subjects | geophysics; tectonics; Nature and Environment; Science and Technology; Health and Safety; earthquakes; aftershocks; seismology; seismic waves; seismic data; earthquake magnitudes; seismological network;
bedrock geology; structural features; faults; fault zones; earthquake mechanisms; 24 April 2014 Vancouver Island Earthquake; Cascadia Subduction Zone; Nootka Fault Zone; North American Plate; Juan de Fuca Plate; Explorer Plate; Methodology |
| Illustrations | location maps; geoscientific sketch maps; tables; seismograms; spectra; time series; plots |
| Program | Public Safety Geoscience Assessing Earthquake Geohazards |
| Released | 2020 12 22 |
| Abstract | In this article, we examine the 24 April 2014 Mw 6.4 earthquake offshore Vancouver Island using a surface-wave empirical Green's function (EGF) deconvolution method and compare the results with SeaJade
II double-difference aftershock locations. The 24 April event was well recorded and provides the first opportunity to evaluate the suitability of surface-wave EGF deconvolution to constrain rupture details for moderate-sized earthquakes in areas
lacking dense seismic arrays. Our surface-wave EGF deconvolution results agree with the aftershock distribution and previously determined centroid moment tensor results. This agreement suggests that this technique is valid for events of this
magnitude in a sparsely networked region. We used an Mw 5.3 earthquake about 21 km from the 24 April epicenter as the primary EGF source event and applied stacking to improve the signal-to-noise ratio. Our analysis used broadband seismic data from
105 regional and teleseismic stations. Given the small magnitudes of these events, an aftershock (Mw 4.8) was considered a secondary EGF source to verify key observations. The relative source time functions obtained from this study reveal an overall
rupture direction of 143°±6°, extent of 28±2 km, and duration of 16.7±0.3 s. We also determined that the rupture occurred in multiple, distinct subevents, but the deconvolution was unable to determine the subevent parameters. Double-difference
aftershock relocations using both onshore and offshore seismometers indicate a 32±2 km unilateral rupture with strike of 146°±2°. These independently determined rupture parameters agree with previously determined centroid moment tensor results with a
nodal plane striking 150°±6°. |
| Summary | (Plain Language Summary, not published)
In this study we examine the rupture characteristics of the M6.6 offshore Vancouver Island earthquake of April, 2014. As one of the largest, and more
recent earthquakes in southwest BC, it provides a unique opportunity to look at details of the rupture and help examine offshore faults. Using local, regional, and global seismic data we find rupture along a previously unrecognised NW-SE trending
fault, with slip occurring along 28-km-long segment of this fault. We find excellent agreement with the aftershock distribution and the focal mechanism (style of faulting) solution. We have modified analysis techniques in this study to make this
methodology useful for smaller (M6) earthquakes, and so many more applications. |
| GEOSCAN ID | 315651 |
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