Recent tectonics of the Blanco Ridge, eastern blanco transform fault zone
Purchase on Springer.com
$39.95 / €34.95 / £29.95*
Rent the article at a discountRent now
* Final gross prices may vary according to local VAT.
Bathymetric, hydro-acoustic, seismic, submersible, and gravity data are used to investigate the active tectonics of the eastern Blanco Transform Fault Zone (BTFZ). The eastern BTFZ is dominated by the ∼150 km long transform-parallel Blanco Ridge (BR) which is a right-lateral strike-slip fault bordered to the east and west by the Gorda and Cascadia Depressions. Acoustic locations, fault-parameter information, and slip vector estimates of 43 earthquakes (M w≥3.8) that occurred along the eastern BTFZ over the last 5 years reveal that the Blanco Ridge is a high-angle right-lateral strike-slip fault, with a small component of dip-slip motion, where the Juan de Fuca plate is the hanging wall relative to the Pacific plate. Furthermore, the Cascadia and Gorda basins are undergoing normal faulting with extension predominantly oblique to the transform trend. Seafloor submersible observations agree with previous hypotheses that the active transform fault trace is the elongate basin that runs the length of the BR summit. Brecciated and undeformed basalt, diabase, and gabbro samples were collected at the four submersible survey sites along the Blanco Ridge. These petrologic samples indicate the Blanco Ridge is composed of an ocean crustal sequence that has been uplifted and highly fractured. The petrologic samples also appear to show an increase in elevation of the crustal section from east to west along the Blanco Ridge, with gabbros exposed at a shallower depth farther west along the southern (Pacific plate side) BR ridge flank. Further supporting evidence for BR uplift exists in the seismic reflection profiles across the BR showing uplift of turbidite sequences along the north and south ridge base, and gravity and magnetics profiles that indicate possible basement uplift and a low-density zone centered on the ridge's Pacific plate side. The BR formation mechanism preferred here is first, uplift achieved partially through strike-slip motion (with a small dip-slip component). Second, seawater penetration along the fault into the lower crust upper mantle, which then enhanced formation and intrusion of a mantle-derived serpentinized-peridotite diapir into the shallow ocean crust, causing further uplift along the fault.
- Abrams, L.J., Detrick, R.S. and Fox, P.J., 1988. Morphology and crustal structure of the Kane fracture zone transverse ridge, J. Geophys. Res. 93: 3195–3210.
- Aki, K. and Richards, P.G., 1980. Quantitative Seismology, Theory and Methods, W.H. Freeman and Company, New York.
- Batiza, R. and Vanko, D., 1983. Volcanic development of small oceanic central volcanoes on the flanks of the East Pacific rise inferred from narrow beam echo sounder surveys, Marine Geology 54: 53–90.
- Bibee, L. D., 1986. Ocean Bottom Seismometer Measurements on the Gorda Ridge. Open-File Report O–86–15, State of Oregon Dept. of Geology and Mineral Industries, 25 pp.
- Bergman, E.A. and Solomon, S.C., 1988. Transform fault earthquakes in the North Atlantic: source mechanism and depth of faulting, J. Geophys. Res. 93: 9027–9057.
- Bonatti, E., 1976. Serpentinite intrusions in the oceanic crust, Earth Plan. Sci. Letts., 32: 107–113.
- Bonatti, E., 1978. Vertical tectonism in oceanic fracture zones, Earth Planet. Sci. Lett. 78: 420–426.
- Braunmiller, J., Leitner, B. and Nabelek, J., 1994. Monitoring Seismic Activity alongthe Blanco Fracture Zone with Regional Broad-Band Data, Eos, Trans. Amer. Geophys. Union 75: 476.
- Clague, D.A. and Holmes, M.L., 1987. Geology, petrology, and mineral potential of the Gorda Ridge, in Sholl, D.W., Grantz, A. and Vedder, J.G. (eds.), Geology and Resource Potential of the Continental Margin of Western North America and Adjacent Ocean Basins-Beaufort Sea to Baja California, Circum-PacificCouncil for Energy and Mineral Resources Earth Science Series Vol. 6: 563–580.
- Craig, C.H. and MacKenzie, D., 1986. The Existence of a Thin, Low Viscosity Layer Beneath the Lithosphere. Earth Planet Sci Lett. 78: 420–426.
- deCharon, A.V., 1988. Structure and Tectonics of the Cascadia Segment, Central Blanco Transform Fault Zone, M.S. Thesis, Oregon State University, Corvallis, Oregon.
- DeMets, C., Gordon, R.G., Argus, D.F. and Stein, S., 1990. Current plate motions, Geophys. J. Int. 101: 425–478.
- Dziak, R.P., Fox, C.G. and Embley, R.W., 1991. Relationship between the seismicity and geologic structure of the Blanco Transform Fault Zone, Mar. Geophys. Res. 13: 203–208.
- Dziak, R.P., Fox, C.G., Embley, R.W., Lupton, J.L., Johnson, G.C., Chadwick, W.W., Koski, R.A., 1996. Detection of and response to a probable volcanogenic T-wave event swarm on the western Blanco Transform Fault Zone, Geophys. Res. Lett. bf 23: 873–876.
- Embley, R.W., 1985. A locally formed deep-ocean canyon system along the Blanco Transform, Geo-Marine Lett. 5: 99–104.
- Embley, R.W., Kulm, L.D., Massoth, G., Abbott, D. and Holmes, M., 1987. Morphology, structure, and resource potential of the Blanco Transform Fault Zone, In Sholl, D.W., Grantz, A. and Vedder, J.G., (eds.), Geology and Resource Potential of the Continental Margin of Western North America and Adjacent Ocean Basins – Beaufort Sea to Baja California, Circum-Pacific Council for Energy and Mineral Resources Earth Science Series, Vol. 6, pp. 549–562.
- Embley R.W. and Wilson, D.S., 1992. Morphology of the Blanco Transform Fault Zone – NE Pacific: implications for its tectonic evolution. Mar. Geophys. Res. 14: 25–45.
- Epp, D., 1984. Possible perturbations to hotspot traces and implications for the origin and structure of the line islands, J. Geophys. Res. 89: 11273–11286.
- Fisk, M.R., Duncan, R.A., Fox, C.G. and Witter, J.B., 1993. Emergence and petrology of the Mendocino Ridge, Mar. Geophys. Res. 15: 283–296.
- Fox, C.G., Dziak, R.P., Matsumoto, H. and Schreiner, A.E., 1994. Potential for monitoring low-level seismicity on the Juan de Fuca Ridge using fixed hydrophone arrays, Mar. Tech. Soc. 27: 22–30.
- Francis, T.J.G., 1981. Serpentinization faults and their role in the tectonics of slow spreading ridges, J. Geophys. Res. 86: 11616–11622.
- Griggs, G.B. and Kulm, L.D., 1973. Origin and development of cascadia deep-sea channel, J. Geophys. Res. 9: 6325–6339.
- Hart, R., Pyle, D. and Robbins; J., 1990. Multistage hydrothermal systems in the Blanco Fracture Zone, In McMurray, G.R. (ed.), Gorda Ridge, Seafloor Spreading Center in the United States' Exclusive Economic Zone, Springer-Verlag, New York, pp. 51–76.
- Hekinian, R., Bideau, D., Cannat, M., Francheteau, J. and Hebert, R., 1992. Volcanic activity and crust-mantle exposure in the ultrafast garret transform fault near 13280 S in the Pacific, Earth Planet Sci Lett. 108: 259–275.
- Ibach, D.H. 1981. The Structure and Tectonics of the Blanco Fracture Zone. M.S.Thesis, Oregon State University, Corvallis, Oregon, 60 pp.
- Ihmle, P.F. and Jordan, T.H., 1994. Teleseismic search for slow precursors to large earthqaukes, Science 266: 1547–1551.
- Kastens, K.A., MacDonald, K.C. and Becker, K., 1979. The Tamayo transfrom fault in the mouth of the Gulf of California, Mar Geophys. Res. 4: 129–151.
- Kastens, K.A., Ryan, W.B.F. and Fox, P.J., 1986. Structural and volcanic expression of a fast slipping ridge-transform-ridge plate boundary: sea Marc I and photographic surveys at the Clipperton transform fault, J. Geophys. Res. 91: 3469–3488.
- Koski, R.A., Embley, R.W., Ross, S.L., Dziak, R.P., Bohannon, R.G., Smith, V.K., Reid, J.A., Gray, L.B. and Tormanen, T.O., 1994. Tectonism and lithologic variation along the Blanco Ridge, Eastern Blanco Fracture Zone, NE Pacific: preliminary results from the PACNORWEST III cruise, Eos, Trans. Amer. Geophys. Union 75: 656.
- Lonsdale, P., 1985. Non-transform offsets of the Pacific-Cocos plate boundary and their traces on the rise flank, Geo. Soc. Amer. Bull. 96: 313–329.
- Macdonald, K.C., Fox, P.J., Alexander, R. T., Pockalny, R. and Gente, P., 1996. Volcanic growth faults and the origin of Pacific Abyssal Hills, Nature 380: 125–129.
- McDonald, M.A., Webb, S.C., Hildebrand, J.A. and Cornuelle, B.D., 1994. Seismic structure and anisotropy of the Juan de Fuca Ridge at 45° N, J. Geophys. Res. 99: 4857–4873.
- Mount, V.S. and Suppe, J., 1992. Present-day stress orientations adjacent to active strike-slip faults: California and Sumatra, J. Geophys. Res. 97: 11995–12013.
- Nabelek, J. and Xia, G., 1995. Regional and teleseismic analysis of the 29 March, 1993. Scotts Mills, Oregon, earthquake, Geophys. Res. Lett. 22: 13–16.
- National Earthquake Information Center, 1992. Preliminary Determination ofEpicenters Catalog, October.
- Oppenheimer, D.H., Reasonberg, P.A. and Simpson, R.W., 1988. Fault plane solutions for the 1984 Morgan Hill, California earthquake sequence: evidence for the state of stress on the Calaveras Fault, J. Geophys. Res. 92: 421–439.
- Pockalny, R.A., Fox, P.J., Fornari, D.J., Macdonald, K.C. and Perfit, M.R., 1997. Tectonic reconstructions of the Clipperton and Siqueiros Fracture Zones: evidence and consequences of plate motion change for the last 3 Myr. J. Geophys. Res. 102: 3167–3181.
- Riddihough, R.P., Seemann, D.A. and Price, W.R., 1982. Juan de Fuca Plate Map: JFP-8 Gravity Anomaly. Earth Physics Branch: Department of Energy, Mines, and Resources, Ottawa, Canada.
- Riddihough, R.P., 1984. Juan de Fuca Plate Map: JFP-11 Magnetic Anomaly, Open File 85–20. Pacific Geoscience Centre, Earth Physics Branch, Department of Energy, Mines, and Resources, Sidney, B.C. Canada.
- Sibson, R.H., 1986. Earthquakes and rock deformation in Crustal Fault Zones, Ann. Rev. Earth Planet. Sci. 14: 149–175.
- Thompson, G. and Melson, W.G., 1972. The petrology of oceanic crust across fracture zones in the Atlantic Ocean: evidence for a new kind of seafloor spreading, J. Geol. 80: 526–538.
- Tobin, D.G. and Sykes, L.R., 1968. Seismicity and tectonics of the Norhteast Pacific Ocean, J. Geophys. Res. 94: 3076–3089.
- Wang, K., He, J. and Davis, E.E., 1997. Transform push, oblique subduction resistance, and intraplate stress of the Juan de Fuca Plate, J. Geophys. Res. 102: 661–674.
- Wilson, D.S., Hey, R.N. and Nishimura, C., 1984. Propagation as a mechanism of reorientation of the Juan de Fuca Ridge, J. Geophys. Res. 89: 9215–9225.
- Wilson, D.S., 1989. Deformation of the so-called Gorda Plate, J. Geophys. Res. 94: 3065–3075.
- Wilson, D.S., 1993. Confidence intervals for motion and deformation of the Juan de Fuca Plate, J. Geophys. Res. 98: 16053–16071.
- Yeats, R.S., Sieh, K. and Allen, C.R., 1997. The Geology of Earthquakes, Oxford University Press, 503 pp.
- Recent tectonics of the Blanco Ridge, eastern blanco transform fault zone
Marine Geophysical Researches
Volume 21, Issue 5 , pp 423-450
- Cover Date
- Print ISSN
- Online ISSN
- Kluwer Academic Publishers
- Additional Links
- Blanco transform fault zone
- ridge formation
- Industry Sectors
- Author Affiliations
- 1. Cooperative Institute for Marine Resources Studies, Oregon State University, Hatfield Marine Science Center, Newport, OR 97365, USA
- 2. National Oceanic and Atmospheric Administration, Pacific Marine Environmental Laboratory, Hatfield Marine Science Center, Newport, OR 97365, USA
- 3. College of Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
- 4. United States Geological Survey, MS999 345 Middlefield Rd, Menlo Park, CA , 94025, USA