Effects of geothermal development on deformation in the Long Valley Caldera, eastern California, 1985-1994

Journal of Geophysical Research B: Solid Earth
By: , and 

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Abstract

Long Valley caldera in east central California has been the site of crustal unrest in the form of seismicity and ground deformation in response to magmatic inflation since 1980. Uplift of the resurgent dome has totaled ∼0.6 m over the 1975–1992 period. Within this region of uplift, and near the southwestern edge of the resurgent dome, is the Casa Diablo area, which experienced relative subsidence of 0.17 m between 1985 and 1992. Geothermal fluid production began at Casa Diablo in 1985 to supply a binary electric power plant; currently, three such plants generate a total of about 40 MW of electricity. The plants are supplied by 170°C water pumped from depths near 150m; all the produced water is reinjected at cooler temperatures at depths near 600 m. Analyses of data from (1) regional leveling lines and a network of bench marks in the geothermal well field area, (2) tilt observations from an L‐shaped array of bench marks, and (3) calculations relating pressure and temperature changes to subsidence indicate that relative subsidence at Casa Diablo results mainly from reductions in pressure in the shallow production reservoir and overlying formations and reductions in temperature in the underlying injection reservoir. Secondary effects on deformation are caused by offsets along the Taylor‐Bryant fault bounding the west side of the well field.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Effects of geothermal development on deformation in the Long Valley Caldera, eastern California, 1985-1994
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1029/95JB00955
Volume 100
Issue B7
Year Published 1995
Language English
Publisher American Geophysical Union
Contributing office(s) Volcano Hazards Program, California Water Science Center
Description 12 p.
First page 12475
Last page 12486
Country United States
State California
Other Geospatial Long Valley Caldera