| Title | Utilizing Ground Penetrating Radar and Infrared Thermography to Image Vents and Fractures in Geothermal Environments |
|---|---|
| Authors | Dougherty, Amy J.; Lynne, Bridget Y. |
| Year | 2011 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Geothermal geology; Vents; Fractures; Ground penetrating radar (GPR); Infrared (IR) thermography |
| Abstract | Fractures and vents commonly occur in geothermal settings. They may act as conduits channeling either gases and/or thermal fluid to the surface from a deeper geothermal reservoir. Where alkali chloride fluids have discharged at the surface, through either vents or fractures, sinter deposits form around these features. Over time, fractures and vents may self-seal and/or become inactive. The sinter that preserves these features can remain at the surface for thousands of years after spring flow has ceased, providing the only surface evidence of the once discharging reservoir fluid. Often hot spring vents are aligned along fractures. In geothermal environments knowledge of faults has been limited to deep geophysics and exposures available for surface mapping. The aim of this research is to display the utility of ground-penetrating radar (GPR) to image vent and fracture pathways and their shallow subsurface directionality and/or connectivity (<20 m depth). This study is part of a more comprehensive study into the applicability of this geophysical tool in mapping the shallow subsurface of geothermal areas. GPR transmits short pulses of high-frequency electromagnetic energy into the ground and detects the reflected signals identifying buried objects or boundary surfaces. GPR has been successfully utilized in many geologic settings, including mapping rock fractures, but our research is the first to utilize this geophysical technique in a range of geothermal environments. Also, ascending steam and gases may escape at the surface through open fractures or more diffusely through the ground surface. Infrared imagery has been shown to be useful for tracking heat flow pathways in these settings. The combination of GPR with infrared thermography has proved successful in imaging vents and fractures as well as areas of elevated temperature in geothermal environments where there is no present-day surface activity. This combined technique provides great potential to assist in the exploration of blind geothermal systems. |