Aquifer characterization using audiomagnetotelluric data (Majorca Island, Spain)
Abstract
The Llucmajor aquifer system (southern Majorca, Spain) presents a zone with hydrothermal evidences whose origin was not well known. As hypothesis, a simple model with two aquifers was proposed: An upper and unconfined aquifer, and a deeper and confined one. The former is currently exploited, and the latter would supply the warm water. In order to verify this hypothesis and to locate the best emplacement for an exploratory well, an audiomagnetotelluric (AMT) survey was carried out in this area. The survey consisted of 42 sites covering an area of 10 km2. This method was suggested since the high resistive structures on the surface do not permit the DC methods to penetrate. The fieldwork allowed us to characterize the geoelectrical properties of the main subsurface structures up to 400 m depth. Three main geoelectrical structures were identified: a shallow high resistive media with an averaged thickness of 150 m; below of it, a low resistive layer of variable thickness, and a deeper resistive medium. The resistive structures were associated to aquifer units, and the conductive one, to the confining unit. The area for the location of the well was suggested where the deeper resistive medium was shallower and the confining unit was thinner. The exploratory well was recently done and reached 530 m depth. The preliminary geological information of the well agreed with the geoelectrical image determined by the AMT data. The well data allowed us to relate the lithology with the geoelectrical properties of the model.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....10697A