The Use of Microearthquakes in Prospecting for Geothermal Areas and Magma Chambers

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Microearthquakes have been observed in nearly all major geothermal areas where detailed recordings have been made. These small earthquakes when recorded over a period of months are primarily confined within the geothermal areas. Such observations suggest that microearthquakes are an important part of those geothermal areas where sufficient heat transfer is taking place to allow economic production of geothermal power under present technology. These earthquakes seem to occur on the fracture systems that allow convection of heat to the surface. The tectonic stress shown by the earthquakes may be necessary to continue creating fresh surfaces for sufficient heat transfer. The ... continued below

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160-168

Creation Information

Ward, Peter L. & Koyanagi, Robert January 1, 1974.

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This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this article can be viewed below.

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  • Geothermal Energy Program (U.S.)
    Publisher Info: DOEEEGTP (USDOE Office of Energy Efficiency and Renewable Energy Geothermal Tech Pgm)
    Place of Publication: United States

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Description

Microearthquakes have been observed in nearly all major geothermal areas where detailed recordings have been made. These small earthquakes when recorded over a period of months are primarily confined within the geothermal areas. Such observations suggest that microearthquakes are an important part of those geothermal areas where sufficient heat transfer is taking place to allow economic production of geothermal power under present technology. These earthquakes seem to occur on the fracture systems that allow convection of heat to the surface. The tectonic stress shown by the earthquakes may be necessary to continue creating fresh surfaces for sufficient heat transfer. The strength of the rocks in major geothermal areas may also be reduced when the hot water leaches silica and other elements allowing the local tectonic stress to be released as small earthquakes. Whatever the explanation, studies of microearthquakes in major geothermal areas seem useful for trying to understand the subsurface structure of these areas and thus locating regions of convective heat transfer. Research in the US for locating magma chambers is still inadequate. Some evidence of magma chambers in the Katmai area of Alaska was reported by Kubota and Berg and Matumoto on the basis of earthquake locations, absence of some S-waves, and attenuation of high-frequency waves. Work on the unique Hawaiian volcanoes has failed so far to show clear seismic evidence of magma chambers even though deformation data imply that magma is stored at shallow depth in the summit and east rift areas. S-waves are not recorded sharply at most stations, and attenuation of high-frequency waves is observed in some areas. No significant gaps in earthquake distribution with depth have been clearly identified yet. Magma chambers in Hawaii may be plexuses of small conduits rather than large chambers. The studies of earthquake locations and lateral changes in seismic-wave attenuation appear quite useful for studying the subsurface structure of areas of value for utilization of volcano energy. Caution must be used, however, in interpreting the data for use in siting drill holes. Locations of earthquakes to an accuracy of 1 km in position or depth, for example, is very difficult, particularly in a volcanic region where lateral changes in velocity can be significant. Considerable effort will be needed to locate earthquakes in these areas with an accuracy of a few hundreds of meters.

Physical Description

160-168

Source

  • U.S.-Japan cooperative science seminar on the utilization of volcano energy, Hilo, Hawaii, USA, 4 Feb 1974

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  • Report No.: CONF-740209--8A
  • Grant Number: None
  • Office of Scientific & Technical Information Report Number: 891990
  • Archival Resource Key: ark:/67531/metadc873830

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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Creation Date

  • January 1, 1974

Added to The UNT Digital Library

  • Sept. 21, 2016, 2:29 a.m.

Description Last Updated

  • Dec. 9, 2016, 7:35 p.m.

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Ward, Peter L. & Koyanagi, Robert. The Use of Microearthquakes in Prospecting for Geothermal Areas and Magma Chambers, article, January 1, 1974; United States. (digital.library.unt.edu/ark:/67531/metadc873830/: accessed June 24, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.