A magnetotelluric transect in the Oregon Coast Range

Young, Charles T.; Kitchen, Mark R.

doi:10.1029/jb094ib10p14185

Cited by 13 publications

(8 citation statements)

References 15 publications

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“…A lower crustal conductor beneath the aseismic front to the west in northeastern Japan has suggested the presence of H2O (e.g., Utada, 1987). Beneath the Oregon coast and Vancouver Island in North America, a high conductivity layer on the top of the descending Juan de Fuca plate has been observed, and lends itself to the inference of H2O-charged sediments that are partially subducted with the oceanic crust (e.g., Wannamaker et al, 1989;Young and Kitchen, 1989;Kurtz et al, 1990). A similar conductive layer has also been proposed in the Japan arc subduction zone by Utada (1987 …”

Section: Comparison With Heat Flow Temperaturementioning

confidence: 73%

H2O and Magmatism in Island Arc Mantle Inferred from Seismic Anelasticity and Heat Flow Data.

Sato

1994

J,Phys,Earth

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Section: Comparison With Heat Flow Temperaturementioning

confidence: 73%

H2O and Magmatism in Island Arc Mantle Inferred from Seismic Anelasticity and Heat Flow Data.

Sato

1994

J,Phys,Earth

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“…In recent years, a few magnetotelluric surveys have been conducted over the Midcontinent Rift (Wunderman, 1986(Wunderman, , 1988Young and Repasky, 1986;Wunderman and Young, 1987a, b; The Midcontinent Rift System Young et al, 1989). These surveys have been useful for studying the electrically conductive, off-rift sedimentary basins, the gross structure of the rift-rock package, and pre-rift basement lithologic variations.…”

Section: Other Geophysical Studiesmentioning

confidence: 99%

The Midcontinent Rift System: A major Proterozoic continental rift

Hinze¹,

Allen²,

Braile³

et al. 1997

Middle Proterozoic to Cambrian Rifting, Central North America

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“…One-dimensional conductivity models of individual MT soundings are very popular because the algorithms fit easily on desktop computers, but these models frequently are suspect due to common departures from one-dimensionality in nature. They can be valuable in constructing initial guesses for subsequent two-dimensional modeling [Waff et al, 1988, Livelybrooks et al, this issue;Young and Kitchen, this issue].…”

Section: Source Fields and Tensor Relationshipsmentioning

confidence: 99%

Magnetotelluric observations across the Juan de Fuca Subduction System in the EMSLAB Project

Wannamaker¹,

Booker²,

Filloux³

et al. 1989

J. Geophys. Res.

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A magnetotelluric (MT) transect has been obtained near latitude 45"N from the active Juan de Fuca spreading center, across the subduction ,..one and Cascades volcanic arc, and into the back arc Deschutes Basin region. This paper presents the MT dat.a set and describes ~ts major characteristics as they pertain to the resistivity of the subduction system. In addition, we discu~s the measurement and processing procedures employed as well as important concerns in data interpretation. Broadband audiomagnetotelluric (AM1)/MT soundings (approx. 0.01-500 s period) were collectei on land with considerable redundancy in site location, and from which 39 sites were selected which con~train upper crustal heterogeneity but sense also into the upper mantle. Fifteen long-period MT recordings (about 50-10,000 s) on land confinn the broadband responses in their common period range and extend the d,:pths of exploration to hundreds of kilometers. On the Juan de Fuca plate offshore, 33 out of 39 sea floor instruments at 19 locations gave good results. Of these locations, five magnetotelluric soundings plus two additional geomagnetic variation sites, covering the period range 200-1OS s approximately, constitute the ocean bottom segment of our profile. The feature of the land observations which probably relates most closely to the subduction process is a peak in the impedance phase of the transverse magnetic mode around 30-50 s period. This phase anomaly, with a corresponding inflection in the apparent resistivity, is continuous eastward from the seacoast and ends abruptly at the High Cascades. It signifies an electrically conductive layer in otherwise resistive lower crust or upper mantle, with the layer conductance decreasing eastward from the coast to a minimum under the Coast Range but increasing suddenly to the east of the central WillanIette Basin. The higher conductance to the east is corroborated by the vertical magnetic field transfer function whose real component shows negative values in the period range 100-1000 s over the same distance. The transverse electric mode apparent resistivity and phase on the land display a variety of three-dimensional effects which make their interpretation difficult. Conversely, both modes of the ocean floor soundings exhibit a smooth progression laterally from the coastal area to the spreading ridge, indicating that the measurements here are reflecting primarily the large-scale tectonic structures of interest and are little disturbed by small near-surfac.e inhomogeneities. The impedance data near the ridge are strongly suggestive of a low-resistivity asthenosphere beneath resistive Juan de Fuca plate lithosphere. Approaching the coastline to the east, both impedance and vertical magnetic field responses appear increasingly affected by a thick wedge of deposited and accreted sediments and by the thinning of the seawater.

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A magnetotelluric transect in the Oregon Coast Range

Cited by 13 publications

References 15 publications

H2O and Magmatism in Island Arc Mantle Inferred from Seismic Anelasticity and Heat Flow Data.

H2O and Magmatism in Island Arc Mantle Inferred from Seismic Anelasticity and Heat Flow Data.

The Midcontinent Rift System: A major Proterozoic continental rift

Magnetotelluric observations across the Juan de Fuca Subduction System in the EMSLAB Project

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