J. J. Ledo

Vertical collapse origin of Las Cañadas caldera (Tenerife, Canary Islands) revealed by 3-D magnetotelluric inversion

Tenerife island geology is one of the most complexes of the Canaries archipelago. This complexity is evidenced by the existing controversy regarding the lateral or vertical collapse origin of the Las Canadas caldera. The resistivity structure of the Las Canadas caldera has been determined by the 3-D inversion of 188 broadband magnetotelluric data. The resistivity distribution obtained in the final model shows clear evidences of the presence of a vertical structure under the Teide, associated to the buried northern wall of the caldera. Additionally, the characteristics of the main resistivity structure, a ring-shaped low-resistivity body (<10 Ω m) interpreted as a hydrothermal clay alteration cap, would point out the presence of a handwall for the Icod Valley lateral landslide located under the Teide, but not in the southern caldera wall (current wall). All these support the vertical collapse hypothesis to explain the origin of the Las Canadas caldera.

A land controlled-source electromagnetic experiment using a deep vertical electric dipole: experimental settings, processing, and first data interpretation

A multichannel borehole-to-surface controlled-source electromagnetic experiment was carried out at the onshore CO2 storage site of Hontom´in (Spain). The electromagnetic source consisted of a vertical electric dipole located 1.5 km deep, and the electric field was measured at the surface. The subsurface response has been obtained by calculating the transfer function between the transmitted signal and the electric field at the receiver positions. The dataset has been processed using a fast processing methodology, appropriate to be applied on controlled-source electromagnetics (CSEM) data with a large signal-to-noise ratio. The dataset has been analysed in terms of data quality and repeatability errors, showing data with low experimental errors and good repeatability. We evaluate if the induction of current along the casing of the injection well can reproduce the behaviour of the experimental data.