## 2 Materials and Methods  
The V-FullWaver (described in detail here: [[http://www.iris-instruments.com/Pdf_file/FullWaver_Gb.pdf](http://www.iris-instruments.com/Pdf_file/FullWaver_Gb.pdf)]([http://www.iris-instruments.com/Pdf_file/FullWaver_Gb.pdf](http://www.iris-instruments.com/Pdf_file/FullWaver_Gb.pdf)), accessed 2 February 2024) is an independent system specifically designed for precise full-waveform time-domain-induced polarization, resistivity, and SP measurements. Each system is fully self-contained, integrating its own power source, a GPS module, and digital memory that can store data for up to three months of continuous recording.  
The FullWaver system is essentially a dual-channel receiver for induced polarization, resistivity, and SP. It is a quasi-cableless system [22] where injection and recording devices come as separate hardware, the recording devices operate autonomously and are not connected by cables, and there is no multiplexer (see Figure 1). FullWaver operates with a constant recording at a 10 ms sample rate, providing a comprehensive waveform record. An added bonus of the equipment is that it can filter out some of the noise which was to be expected at this site. Each autonomous measuring station includes three potential electrodes, typically placed in perpendicular directions. In this arrangement, all the geoelectric measurements are in two perpendicular directions. This permits the creation of a \"true\" subsurface 3D, as opposed to the \"pseudo 3D\" created with parallel Electrical Resistivity Tomography (ERT) profiles. Herein lies one of the key advantages of this approach compared to conventional geoelectrical measurements. A real geoelectrical 3D subsurface of the volcano is desirable in this case.  
The recorded time-series by the V-FullWaver can be post-processed using dedicated software. The software enables various processing steps such as improving the signal-to-noise ratio, focusing on stable and accurate parts of the signal, removing SP spikes, and resynchronizing the data if necessary.  
Some advantages of the FullWaver make it particularly well suited to the study of mud volcanoes. The FullWaver devices, including the V-FullWaver, are designed for the measurement of resistivity, IP, and PS on large 3D surfaces, which can be affected by sharp topography, as is the case at Paclele Mici (see Figure 2). The array is not bound by any particular geometry (i.e., Wenner) and can be customized depending on the desired survey objective. Depending on the size of the area to investigate, multiple V-FullWaver devices can be located in any desired way on the surface of the investigation, performing continuous measurements.  
Another advantage of this type of objective is the current injection system. The system can use a pseudo-pole-dipole system with one electrode fixed \"at infinity\" and one mobile injection station. Here, we use the VIP10000 which can output up to 6000 V peak to peak and 20 A. The ability to inject strong current was useful at this conductive site, enabling deeper penetration. The realization of true 3D subsurface visualization was also an important advantage of this system.  
Although the methodology is different, the underlying physical processes are largely similar to ERT. Parameters controlling the depth of investigation and the depth of penetration are still the length of the transmitting line and the distance between transmitters and receivers [6]. The maximum estimated depth of investigation is 156 m.  
At the end of the survey, the data were copied from each FullWaver device. The electrode coordinates have been entered into the devices, and an automatic process was used to export the resistivity and IP data in Prosys II.  
Figure 1: A measuring station on the mud volcano surface.