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Imaging Thermal Anomalies in Hot Dry Rock Geothermal Systems from Near-Surface Geophysical Modelling

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Gomez-Ortiz, David and Blanco-Montenegro, Isabel and Arnoso, José and Martin-Crespo, Tomas and Solla, Mercedes and Montesinos, F. G. and Vélez, Emilio and Sánchez, Nieves (2019) Imaging Thermal Anomalies in Hot Dry Rock Geothermal Systems from Near-Surface Geophysical Modelling. Remote Sensing, 11 (6). p. 675. ISSN 2072-4292

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Official URL: https://doi.org/10.3390/rs11060675




Abstract

Convective hydrothermal systems have been extensively studied using electrical and electromagnetic methods given the strong correlation between low conductivity anomalies associated with hydrothermal brines and high temperature areas. However, studies addressing the application of similar geophysical methods to hot dry rock geothermal systems are very limited in the literature. The Timanfaya volcanic area, located on Lanzarote Island (Canary Islands), comprises one of these hot dry rock systems, where ground temperatures ranging from 250 to 605 ◦C have been recorded in pyroclastic deposits at shallow (<70m) depths. With the aim of characterizing the geophysical signature of the high ground temperature areas, three different geophysical techniques (ground penetrating radar, electromagnetic induction and magnetic prospecting) were applied in a well-known geothermal area located inside Timanfaya National Park. The area with the highest ground temperatures was correlated with the location that exhibited strong ground penetrating radar reflections, high resistivity values and low magnetic anomalies. Moreover, the high ground temperature imaging results depicted a shallow, bowl-shaped body that narrowed and deepened vertically to a depth greater than 45 m. The ground penetrating radar survey was repeated three years later and exhibited subtle variations of the signal reflection patterns, or signatures, suggesting a certain temporal variation of the ground temperature. By identifying similar areas with the same geophysical signature, up to four additional geothermal areas were revealed. We conclude that the combined use of ground penetrating radar, electromagnetic induction and magnetic methods constitutes a valuable tool to locate and study both the geometry at depth and seasonal variability of geothermal areas associated with hot dry rock systems.


Item Type:Article
Uncontrolled Keywords:Timanfaya volcanic area; HDR geothermal systems; GPR; EMI; Magnetic anomalies; Seasonality
Palabras clave (otros idiomas):Geofísica; Area volcánica del Timanfaya; EMI; Sistemas geotérmicos HDR
Subjects:Sciences > Physics > Geophysics
ID Code:63196
Deposited On:30 Nov 2020 16:36
Last Modified:01 Dec 2020 08:30

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