Joint 1D inversion of TEM and MT resistivity data with an example from the area around the Eyjafjallajökull glacier, S-Iceland

Abstract

Due to the recent eruptive events in Eyjafjallajökull, many projects have been started, collecting more information to gain a deeper understanding about volcanic structures and processes. This can help to better predict the nature and timing of volcanic threats. Glacier covered volcanoes are of special interest since these are phreato-magmatic and capable of producing sudden glacial floods. In order to investigate the resistivity structure beneath and around Eyjafjallajökull glacier, the Dublin Institute for Advanced Studies (DIAS) and Iceland GeoSurvey (ISOR) carried out the first step of an MT survey in 2011 including 26 pairs of MT and TEM soundings around the volcano, where each MT sounding took 2 days to record. The MT (Magnetotelluric) and TEM (Transient Electro Magnetic) methods are far more sensitive to fluid distribution (in this case partial melt) than any other geophysical method, thus leading to this pilot study. TEM soundings were carried out at the same locations as the MT soundings in order to correct for static shifts. A remote reference MT station was running simultaneously at several tens of kilometres distance to allow the state-of-the-art remote-referencing technique to improve the signal to noise ratio. Joint 1D (one-dimensional) inversion of magnetotelluric (MT) and central loop transient electromagnetic (TEM) data was done by fitting both data sets using the same 1D resistivity model.