| Title | Seismic evidence for megathrust fault-valve behavior during episodic tremor and slip |
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| Author | Gosselin, J M; Audet, P ; Estève, C; McLellan, M; Mosher, S G; Schaeffer, A J |
| Source | Science Advances vol. 6, no. 4, eaay5174, 2020 p. 1-6, https://doi.org/10.1126/sciadv.aay5174  Open Access |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20190342 |
| Publisher | American Association for the Advancement of Science |
| Document | serial |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf; html |
| Province | British Columbia |
| NTS | 92B; 92C; 92F/01; 92F/02; 92F/03; 92F/04; 92F/05; 92F/06; 92F/07; 92F/08; 92G/02; 92G/03; 92G/04; 92G/05; 92G/06; 92G/07 |
| Area | Vancouver Island; Victoria; Vancouver; Washington State; Olympic Peninsula; Canada; United States of America |
| Lat/Long WENS | -126.0000 -122.0000 49.5000 47.5000 |
| Subjects | tectonics; structural geology; geophysics; Science and Technology; Nature and Environment; bedrock geology; seismology; earthquakes; structural features; faults; crustal movements; tectonic setting;
subduction zones; shear zones; fluid flow; pore fluids; pore pressures; seismic data; seismic waves; seismic velocities; anomalies; seismological network; Cascadia Subduction Zone; Juan de Fuca Plate; North American Plate; Global positioning
systems |
| Illustrations | geoscientific sketch maps; time series; plots; models |
| Program | Public Safety Geoscience Assessing Earthquake Geohazards |
| Released | 2020 01 22 |
| Abstract | Fault slip behavior during episodic tremor and slow slip (ETS) events, which occur at the deep extension of subduction zone megathrust faults, is believed to be related to cyclic fluid processes that
necessitate fluctuations in pore-fluid pressures. In most subduction zones, a layer of anomalously low seismic wave velocities [low-velocity layer (LVL)] is observed in the vicinity of ETS and suggests high pore-fluid pressures that weaken the
megathrust. Using repeated seismic scattering observations in the Cascadia subduction zone, we observe a change in the seismic velocity associated with the LVL after ETS events, which we interpret as a response to fluctuations in pore-fluid pressure.
These results provide direct evidence of megathrust fault-valve processes during ETS. |
| Summary | (Plain Language Summary, not published)
The Cascadia Subduction Zone in western Canada continues to present arguable the single most significant earthquake hazard to the entire country. Ongoing
research into Cascadia and in fact subduction zones in general, believe that the presence and role play by fluids in the processes governing slip on the fault are of critical importance. In this study, we study in detail a handful of stations across
southern Vancouver Island to examine the potential role fluid migration plays in the role of episodic tremor and slip (ETS) which occur regularly across Cascadia. The results of this work demonstrate that statistically significant changes in across
fault properties occur in the days following an ETS event, which are interpreted to result from changes in the location pore fluid pressure along and near the fault interface. |
| GEOSCAN ID | 321450 |
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