Deep crustal structure of the Cascade Range and surrounding regions from seismic refraction and magnetotelluric data
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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.
Study Area
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 |
DOI | 10.1029/JB095iB12p19419 |
Volume | 95 |
Issue | B12 |
Year Published | 1990 |
Language | English |
Publisher | AGU |
Contributing office(s) | Earthquake Science Center |
Description | 20 p. |
First page | 19419 |
Last page | 19438 |
Country | United States |
State | California, Oregon, Washington |
Other Geospatial | Cascade Range |
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