scholarly journals Seismic structure of the southern Cascadia subduction zone and accretionary prism north of the Mendocino triple junction

1998 ◽  
Vol 103 (B11) ◽  
pp. 27207-27222 ◽  
Author(s):  
Sean P. S. Gulick ◽  
Anne M. Meltzer ◽  
Samuel H. Clarke
Keyword(s):  
Subduction Zone ◽  
Triple Junction ◽  
Accretionary Prism ◽  
Cascadia Subduction Zone ◽  
Seismic Structure ◽  
Mendocino Triple Junction

The northern Cascadia subduction zone at Vancouver Island: seismic structure and tectonic history

1990 ◽  
Vol 27 (3) ◽  
pp. 313-329 ◽  
Author(s):  
R. D. Hyndman ◽  
C. J. Yorath ◽  
R. M. Clowes ◽  
E. E. Davis
Keyword(s):  
Continental Shelf ◽  
Subduction Zone ◽  
Deep Ocean ◽  
Vancouver Island ◽  
Ocean Basin ◽  
Cascadia Subduction Zone ◽  
Accretionary Wedge ◽  
Seismic Structure ◽  
Tectonic History ◽  
Wide Range

The structure and Tertiary tectonic history of the northern Cascadia subduction zone have been delineated by a series of new multichannel seismic lines acquired across the continental shelf to the deep sea, combined with adjacent land multichannel seismic data and results from a wide range of other geophysical and geological studies. The top of the downgoing oceanic crust is imaged for a remarkable distance downdip from the deep ocean basin to a depth of 40 km beneath Vancouver Island. The reflection depths are in good agreement with seismic refraction models and Benioff–Wadati seismicity. Two broad reflective bands imaged as dipping gently landward at depths of about 15 and 30 km on the land lines merge to a single reflector band offshore. They may represent underplated oceanic material or, alternatively, they may not be structural but may be zones of contrasting physical properties, perhaps representing trapped fluid. Two narrow terranes, the Mesozoic marine sedimentary Pacific Rim Terrane and the Eocene marine volcanic Crescent Terrane, have been thrust beneath, and accreted to, the margin in the Eocene, about 42 Ma, near the start of the present phase of subduction. They provide a landward-dipping backstop to the large sediment wedge accreted since that time. The deformation front is characterized by mainly landward-dipping thrust faults that cut close to basement. This result and the mass balance of the incoming sediment compared with that present in the accreted wedge suggest that there is little subduction of sediment into the mantle. The Tofino Basin sediments, up to 4 km in thickness, have been deposited on the continental shelf over the accreted terranes and the developing accretionary wedge.

scholarly journals IODP Expedition 328: Early Results of Cascadia Subduction Zone ACORK Observatory

2012 ◽  
Vol 13 ◽  
pp. 12-18 ◽  
Author(s):  
E. Davis ◽  
M. Heesemann ◽  
Keyword(s):  
Subduction Zone ◽  
Gas Hydrate ◽  
Accretionary Prism ◽  
Cascadia Subduction Zone ◽  
Ocean Drilling Program ◽  
Integrated Ocean Drilling Program ◽  
Early Results ◽  
Large Phase ◽  
Four Levels ◽  
Hydrate Stability

Integrated Ocean Drilling Program (IODP) Expedition 328 was devoted to the installation of an "Advanced CORK" (Circulation Obviation Retrofit Kit) in the Cascadia subduction zone accretionary prism to observe the physical state and properties of the formation as they are influenced by long-term and episodic deformation and by gas hydrate accumulation. Pressures are monitored at four levels on the outside of a standard 10 3/4-inch casing string, two above and two below the base of the gas-hydrate stability zone at 230 mbsf (m below seafloor). The casing was sealed at the bottom, leaving the inside open down to 302 mbsf for installation of a tilt meter, seismometer, and thermistor cable (scheduled for 2013). The initial data, recovered in July 2011, document an initially smooth recovery from the drilling perturbation followed by what may be a sequence of hole-collapse events. Pressure at the deepest screen is roughly 40 kPa above hydrostatic; higher pressures (80 kPa) are observed at the two screens close to the level of hydrate stability. Tidal variations at the deepest screen are in phase with ocean tides, and define a loading efficiency of 0.6, which is reasonable in light of the consolidation state of the for-mation (porosity ~0.5). Tidal signals near the level of gas hydrate stability display large phase lags, probably as a consequence of hydraulic diffusion stimulated by the large contrast in interstitial fluid compressibility at the gas-hydrate boundary. The degree of isolation among the screens, the anticipated good coupling, and the estimated strain-to-pressure conversion efficiency (~5 kPa μstrain<sup>&minus;1</sup>) indicate that this installation will serve well to host a variety of hydrologic, seismic, and geodynamic experiments. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.13.02.2011" target="_blank">10.2204/iodp.sd.13.02.2011</a>

ASSESSING THE UTILITY OF δ13C AND BULK GEOCHEMISTRY IN ESTUARIES ALONG THE CASCADIA SUBDUCTION ZONE FOR COASTAL PALEOSEISMOLOGY

2017 ◽  
Author(s):  
Robert J. O'Donnell ◽  
◽  
Andrea D. Hawkes ◽  
Chad S. Lane ◽  
Simon E. Engelhart ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Cascadia Subduction Zone
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