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U. Riccardi a,d), J. Arnoso b,d), M. Benavent c,d), E. Vélez b,d), U. Tammaro e) and FG. Montesinos c,d)

a) Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse (DiSTAR), University “Federico II” of Naples, Italy
b) Instituto de Geociencias (IGEO, CSIC-UCM). C/ Doctor Severo Ochoa, 7. Facultad de Medicina (Edificio Entrepabellones 7 y 8). 28040 Madrid, Spain
c) Facultad de Matemáticas, Universidad Complutense de Madrid, Plaza de Ciencias 3, 28040 Madrid, Spain
d) Research Group ‘Geodesia’, Universidad Complutense de Madrid, Spain
e) Istituto Nazionale di Geofisica e Vulcanologia, Italy
We report on a detailed geodetic continuous monitoring in Timanfaya Volcanic Area (TVA), where the most intense geothermal anomalies of Lanzarote Island are located. We analyze about three years of GNSS data collected on a small network of five permanent stations, one of which at TVA, deployed on the island, and nearly 20 years of tiltmeter and strainmeter records acquired at Los Camelleros site settled in the facilities of the Geodynamics Laboratory of Lanzarote within TVA. This study is intended to contribute to understanding the active tectonics on Lanzarote Island and its origin, mainly in TVA. After characterizing and filtering out the seasonal periodicities related to “non-tectonic” sources from the geodetic records, a tentative ground deformation field is reconstructed through the analysis of both tilt, strain records and the time evolution of the baselines ranging the GNSS stations. The joint interpretation of the collected geodetic data show that the area of the strongest geothermal anomaly in TVA is currently undergoing a SE trending relative displacement at a rate of about 3 mm/year. This area even experiences a significant subsidence with a maximum rate of about 6 mm/year. Moreover, we examine the possible relation between the observed deformations and atmospheric effects by modelling the response functions of temperature and rain recorded in the laboratory. Finally, from the retrieval of the deformation patterns and the joint analysis of geodetic and environmental observations, we propose a qualitative model of the interplaying role between the hydrological systems and the geothermal anomalies. Namely, we explain the detected time correlation between rainfall and ground deformation because of the enhancement of the thermal transfer from the underground heat source driven by the infiltration of meteoric water.
Legenda Fig 1
Fig. 1. (Left) Shaded reliefmap of Lanzarote Island, located in the Canary Islands (inlet), showing the limits (green line) of Timanfaya National Park, the fissure zone (shaded orange area) of the 1730–1736 volcanic eruption and the location of GNSS stations. (Up-Right) Zoomed reliefmap of the Timanfaya volcanic area (TVA) indicating the position of the GNSS station CAME. (Down-Right) The squared area is a Google Earth image that shows the main thermal anomalies (in orange color) located in the area close to Islote de Hilario (according to Araña et al., 1984), the position of the 13 m deep well (yellow circle) having temperature N600 °C and the Geodynamics Laboratory of Lanzarote (GLL) at the TVA. The two orthogonal lines (LD, TD) represent the respective orientation of the strainmeters and tiltmeters atGLL site.