scholarly journals Erratum to: Geodetic and seismic signatures of episodic tremor and slip in the northern Cascadia subduction zone

2005 ◽  
Vol 57 (4) ◽  
pp. 369-369
Author(s):  
H. Dragert ◽  
K. Wang ◽  
G. Rogers
Keyword(s):  
Subduction Zone ◽  
Cascadia Subduction Zone ◽  
Episodic Tremor And Slip ◽  
Episodic Tremor

scholarly journals Seismic evidence for megathrust fault-valve behavior during episodic tremor and slip

2020 ◽  
Vol 6 (4) ◽  
pp. eaay5174 ◽  
Author(s):  
Jeremy M. Gosselin ◽  
Pascal Audet ◽  
Clément Estève ◽  
Morgan McLellan ◽  
Stephen G. Mosher ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Seismic Velocity ◽  
Fluid Pressure ◽  
Pore Fluid ◽  
Cascadia Subduction Zone ◽  
Low Velocity ◽  
Seismic Scattering ◽  
Fault Valve ◽  
Episodic Tremor

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.

Great earthquakes on Canada’s west coast: a review This article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent. Geological Survey of Canada Contribution 20090196.

2010 ◽  
Vol 47 (5) ◽  
pp. 801-820 ◽  
Author(s):  
Roy D. Hyndman ◽  
Garry C. Rogers
Keyword(s):  
Elastic Strain ◽  
Coastal Region ◽  
Vancouver Island ◽  
Cascadia Subduction Zone ◽  
Slow Slip ◽  
Coastal Cities ◽  
Great Earthquakes ◽  
Multidisciplinary Data ◽  
Episodic Tremor And Slip ◽  
Episodic Tremor

The first Lithoprobe transect in 1984 across Vancouver Island had primary objectives to define the structure associated with subduction and constraints on the potential for great thrust earthquakes. The Lithoprobe results and the comprehensive multidisciplinary data collection and analyses that followed provide compelling evidence for past great earthquakes along the Cascadia subduction zone from Vancouver Island to northernmost California, and for present elastic strain build up toward future great events. There is evidence of sudden coastal subsidence up to 2 m and of deep-sea turbidite deposits indicating strong shaking from huge earthquakes at irregular intervals averaging about 500 years, the last in 1700. Precision geodetic measurements define the present buckling of the coastal region, diagnostic of elastic strain accumulation on a locked thrust fault. The landward extent of rupture and, therefore, shaking at coastal cities is constrained by (i) the pattern of elastic strain buildup, (ii) the estimated temperatures on the fault, (iii) the updip limit of episodic tremor and slip (ETS), (iv) the downdip change in reflection character of the thrust, and (v) the magnitude of coastal subsidence in the most recent, 1700, and previous great events. The major earthquakes are very large, M9, rupturing most of the Cascadia margin, but mainly offshore, limiting somewhat the shaking at inland cities but producing large tsunamis. The ETS that occurs at intervals of just over a year appears to involve slow slip on the subduction thrust downdip of the rupture zone that increases stress on the locked zone and may indicate time varying potential for great events.

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