Study of deformation in the Coso geothermal area, central eastern California

Coso area (outlined by a white square on the topo map of central eastern California) is a site of active geothermal energy production. The Coso geothermal plant, owned by the US Navy and operated by the California Energy Company, is the second largest in the US, with energy output of 300 MW. Our InSAR study reveals a broad subsidence anomaly that approximately coincides with the geothermal production area.
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Figure on the left shows an example of InSAR measurements of the ground deformation at Coso. Shown in the figure is an interferogram formed by subtracting phases of two radar images acquired during successive passes of the ERS2 satellite along the track 170 (area illuminated by a satellite radar is denoted by a black square in the right figure). In this case, a time interval between the two passes of the satellite is nearly 3 years. "Fringes" on the image correspond to changes in distance between the satellite and the Earth surface (the so-called "line-of-sight" displacement); each fringe corresponds to about 3 cm of the line of sight motion.

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We have modeled the observed deformation using elastic solutions for pressurizes elliptical cavities in a uniform half-space. Results of our inversion are shown in the bottom figure. The source depths inferred from our inversion range from 1 to 3 km, which corresponds to the production interval of the Coso geothermal plant. Therefore, we believe that the observed deformation is presumably caused by the withdrawal of geothermal fluids and/or thermal contraction of rocks due to cooling.

For more details, please see this paper.

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