## 3 Results  
Before carrying out the V-FullWaver survey, several test ERT profiles were carried out in the area to confirm the conductive nature of the subsurface and indicate whether the approach is necessary. The profiles confirmed the very low resistivity values, as depicted in the figure below (Figure 3 resistivity values < 1.7 ohm.m). Figure 3: Positioning of a representative ERT profile on the Páclele Mici mud volcano, featuring low resistivity values. Figure 2: A measuring station on an area with sharp topography. Low resistivity values were anticipated. However, the observed values fall even below what was anticipated. A Dipole-Dipole ERT array with 24 electrodes and a distance between electrodes of 5 m showed resistivity values under 2 ohm-meters. As a result, ERT measurements are not expected to provide substantial value in this context because the subsurface is very conductive, and therefore, it is extremely challenging to reach a satisfactory depth of investigation (as the current dissipates). However, other geoelectrical surveys were expected to be of more use. The current that can be injected with conventional ERT equipment will not provide a good enough depth of penetration and will likely not ensure significantly deeper contrasts. The FullWaver survey was thus employed. The survey was carried out over the course of one day. A total of 20 measuring stations were used, as well as injection points displayed thusly. The distance between measuring stations was 50 m in both directions, while the distance between injection stations was 100 m (see Figure 4). Processing was carried out using Prosys III. The first part of the processing was verifying that the time series were synchronized. Eliminated points were noisy, had poor signal, or appeared singularly anomalous. Notably, some points appeared as negative resistivity and were eliminated. Topography corrections were also introduced, using the coordinates of each individual electrode. Overall, however, most points had a satisfactory signal-to-noise ratio. In the end, out of the 801 data points, a total of 748 data points were retained. The signal amplitude of the selected data ranges from 0.013 to 38.02 mV, and the apparent resistivity data range from 0.2 to 8.8 ohm.m. The average value is 1.76, and the median value is 1.6 ohm.m (Figure 5). Figure 4: A map displaying the distribution of measuring stations (in blue) and current injection stations (in red), overlaid on a local DEM. These are very low resistivity values that are explained by mud volcano activity, as the conductive fluid drastically reduces the surrounding resistivity. This is consistent with reported cases in the literature [23] which also mention that mud volcano activity is linked with very low resistivity values. Notably, even in the area outside of the visible surface mud, the values are still very low, suggesting that the active area extends beyond what is visible at the surface. Interpreting the results from spontaneous potential is not attempted here. However, we note that the spontaneous potential variation helps put into perspective just how low the observed resistivity values are (Figure 6). In many instances, the induced potential differences are comparable to or even smaller than the natural spontaneous potential of the site. This suggests that such natural variations can be a significant source of errors given the low resistivity values. Figure 5: Representation of measured data points and their resistivity values and a histogram of the values. Figure 6: Representation of the recordings on one of the V-FullWaver surveys, displaying potential as a function of time. As they record continuously, the SP values would appear with a thinner line in the image, and the injection points are visible with higher amplitude and significantly highlighted. The recording lasted for approximately 17,000 s. A cassette is highlighted for a zoomed-in version (see Figure 7). Unfortunately, the chargeability data are also remarkably unreliable on all stations.