Exploration of Volcanic Geothermal Energy Resources Based on Rheological Techniques. Final Report

摘要

Tidal strain and tilt field observations were carried out during the period February 1978 to December 1979 at the Klamath Graben and Newberry Caldera in Oregon and at Krafla in Northern Iceland. Moreover, tilt observations were made at Mt. St. Helens, Washington, during the summer of 1980. Two strainmeters of the same type as now in use by the US Geological Survey were applied in the strain work. Tilts were measured by two Kinemetrics model TM-1B biaxial tilt meters. The instruments were placed at depths of approximately one to two meters below the ground surface. Both strain and tilt fields turn out to be heavily contaminated by noise that is mostly of thermoelastic origin. In spite of considerable efforts, it has not been possible to process the strain field data to obtain sufficiently clear tidal signals. The tilt data are less contaminated and rather clear tidal signals were observed at Newberry in Oregon and Krafla in Iceland. A local magnification by a factor of about 3 of the EW component of the theoretical solid earth and ocean load tilt was observed at one station at Krafla. Moreover, the tidal tilt component across the ring fault at Newberry appears to be magnified by a factor of 1.4 to 1.9. The phenomena at the Krafla may possibly be due to a local magma chamber. These results are a clear indication of a tilt field modification by local structure and indicate the possibility of using tilt data to locate subsurface magma bodies. (ERA citation 06:012255)