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Deep crustal structure of the Cascade Range and surrounding regions from seismic refraction and magnetotelluric data

Journal of Geophysical Research

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Abstract

Several regional seismic refraction and magnetotelluric (MT) profiles have been completed across the Cascade Range and surrounding geologic provinces in California, Oregon, and Washington. Analysis of three MT and two seismic refraction profiles in Oregon and a coincident MT and refraction profile in northern California show a high degree of correlation between resistivity and velocity models. The main feature that is evident in both data sets is a highly conductive (2-20 ohm m) zone that occurs at depths of 6-20 km and largely within a midcrustal velocity layer of 6.4-6.6 km/s, overlying a lower crust with velocities of 7.0-7.4 km/s. Accretionary structures in the southern Washington Cascades have been shown to be related to stress release in the area of Mount St. Helens. In order to explain the similar structures in the MT and refraction models for Oregon and California, a model is proposed involving the effects of metamorphic zonation to produce the velocity structure, combined with metamorphically produced fluids and partial melt to produce the deep conductor. -from Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Deep crustal structure of the Cascade Range and surrounding regions from seismic refraction and magnetotelluric data
Series title:
Journal of Geophysical Research
Volume
95
Issue:
B12
Year Published:
1990
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article