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Summary of Proposal RES1375

TitleSurface deformation in the Salton Sea Geothermal Field, southern California (USA)
Investigator Eneva, Mariana - Imageair Inc., N/A
Team Member
Operations Manager Falorni, Giacomo - TRE Canada, N/A
Summary

The Imperial Valley in southern California is a region of significant current geothermal operations, as well as intense geothermal development. The most prominent current geothermal operation in this area is the Salton Sea geothermal field (SSGF) on the southern shore of the Salton Sea. It is located within the Salton Trough, which is characterized by ongoing tectonic activity, such as extension, rotation, significant seismicity, and aseismic episodes, all causing surface deformation. In addition, extensive agricultural activity takes place in Imperial Valley, including on the territory of the SSGF. This activity is very sensitive to surface movements, especially land subsidence. It is not trivial to distinguish between tectonic and man-made changes in this region. In the SSGF in particular, no significant fluid level and pressure changes have been observed after more than 30 years of operation, so observed surface deformation may have to be attributed mostly to tectonics. Yet, this view may be challenged with numerous examples of geothermal operations causing surface deformation elsewhere. Therefore, creating a baseline of surface deformation prior to geothermal development is very important, so that interested parties will be able to distinguish in the future between the two sources of surface displacements. Such baseline measurements will help in geothermal development, planning, and exploration. Deformation monitoring is also important for current geothermal operators, such as CalEnergy operating the SSGF, both in their mitigation efforts if their activities are suspect of producing surface changes, or for general monitoring of the surface levels in the fields and planning locations and amounts of fluid re-injection.

The intended collection of TerraSAR-X data will significantly contribute to a current project with the California Energy Commission (CEC), which aims at determining the deformation baseline in Imperial Valley using satellite data and innovative radar interferometry techniques (InSAR). In this project, 2003-2010 Envisat data are being used to obtain time series of surface deformation in thousands of individual locations of permanent and distributed scatterers (PS and DS), and to estimate annual deformation rates. The method used is SqueeSAR, the latest development of PSInSAR provided by the subcontractor on this project, TRE Canada (a subsidiary of TRE Italy). In terms of spatial and temporal coverage, these observations vastly surpass measurements by any other means, such as those provided by localized leveling surveys and the regional GPS network. The agricultural landscape has been a significant barrier to perform any similar work so far, as conventional InSAR techniques, such as differential InSAR, only work in mostly dry, non-vegetated areas. The recent PSInSAR innovations employed in the CEC project make it possible to extract information from vegetated areas as well. This was demonstrated for the first time in a previous project with CEC, on the territory of the SSGF, where we used 2006-2008 Radarsat data, thus laying the groundwork for extending this type of analysis to longer periods and other areas of the Imperial Valley. In the framework of the current CEC project, it would be greatly beneficial to collect TerraSAR-X data, which can be significantly more frequent and with a much spatial resolution, over a specific 25-sq. km portion of the SSGF, determined to be of special interest to its operator, CalEnergy. The results will be interpreted through detailed maps, analyses of spatial and temporal variability, and comparison with other types of data, such as leveling surveys, seismicity, gravity, thermal information, magnetotelluric observations, and aerial orthophotos. This project is expected to provide unprecedented knowledge of surface deformation to the benefit of both the scientific community and the geothermal operators and developers.

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