Geothermal Resource Assessment Of Mount Hood

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ISBN 13 :
Total Pages : pages
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Download or read book Telluric-magnetotelluric Survey at Mount Hood, Oregon written by and published by . This book was released on 1978 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The survey was conducted as part of a geothermal resource assessment study that had the overall objective of stimulating geothermal exploration near stratovolcanoes in the High Cascade Range. A telluric-magnetotelluric (T-MT) survey was chosen as the electrical resistivity technique. Data were collected in overlapping bands from 0.002 to 40 Hz, although high levels of cultural noise, coupled with instrumental problems, decreased the usable high frequency response during the first phase of the two-phase field program. Two specific areas of interest have been identified: (a) Two anomalous near-surface low-resistivity zones occur close to the Cloud Cap eruptive center on the northeast side of the volcano. Anomalous conditions diminish away from the recent (12,000/sup +-/ y.B.P.) vent. The shallower zone (0.5 to 1.0 km in depth) occurs within the Mount Hood volcanic pile and its 2 ohm-m resistivity is difficult to explain. A deeper zone (2/sup +-/ km), of approximately 10 ohm-m, occurs within what may be the pre-Mount Hood Yakima basalts (Miocene), and may have geothermal potential. (b) The strongly linear north-south electric field polarizations observed on the south side could be significant. Warm water emanations in the area suggest faulting, but there is neither direct evidence for faults, nor do the MT results clearly indicate anomalous resistivity conditions at depth. The MT station closest to the warm springs yielded low apparent resistivities which could be explained by conductive rock extending from surface to an undetermined depth. However, these data are incomplete and suspect, both because of severe noise and recorder malfunction at higher frequencies.