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You will find here the five subjects of my researchs by alphabetic order.
(It's recommanded to click on each picture/figure to enlarge it in the new window).

New Zeland
Acquisition of self-potential data during pumping tests
Electrochemistry and Transport in Clays
Mechanical properties
Volcanology and Geothermal Systems

Before to show the research subjects, I will introduce to you the research project " POLARIS":

This project concerns the modeling of induced polarization of porous materials at different scales: (a) in the laboratory (measurements in the temporal and frequency domains, Bayesian inversion of the Cole Cole parameters), relation to the microstructure, relation to the contamination of the pore water (b) sandbox experiments, and (c) field experiments plus forward and inverse modeling.

Various researchers from UMR Sisyphe (Université Paris 6), EGID (Université Bordeaux III), EOST Strasbourg (Université Louis Pasteur), and CEREGE (Université Paul cézanne) are concerned by this project. Several documents related to this project can be downloaded here (pdf format).

Rapport POLARIS - POLARIS Publications

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Electrochemistry and Transport in Clays

Transport in Clay-rich materials

Co-workers: Leroy P. (1, 2), D. Coelho (2), and S. Altmann (2)

(1) CNRS-CEREGE, Dept. d'Hydrogéophysique et Milieux Poreux, Aix-en-Provence, France. (2) ANDRA, 1-7 rue Jean Monnet, 92298 Chatenay-Malabry, France.

Clay-rich media presents several pore scales with micro- and macro-pores plus the interlayer porosity for swelling clays (Figure 1). Because of the charged nature of clay-rich media, the interstitial water contained in their microporosity does not obey the classical electroneutrality condition usually used to derive the ionic composition of reservoir rocks. The requirement of global electroneutrality in the micropores (corresponding to the pores smaller than the size of the diffuse layer, see Figure 2) implies that the net charge density of the pore water balances the deficiency (or the excess) of electrical charge of the clay particles. We generalized the Donnan equilibrium conditions in the case of a multi-ionic electrolyte with partition of the counterions between the Stern and the diffuse layers.

We also derived an expression for the osmotic pressure in the micropores. The calculation of the osmotic pressure and the ionic composition of the pore water in the micropores required the value of the partition coefficient of the counterions between the Stern and the diffuse layers. We used an electrical triple layer model (see Leroy and Revil, 2004) to calculate this partition coefficient. One application of this model was made to the Callovo-Oxfordian argillite used as a test-argillaceous material in various scientific studies carried out over the past decades. We have determined the composition of the solution contained in the micropores using the Donnan equilibrium conditions, the composition of the solution in the macropores in chemical equilibrium with the minerals, and the electrical triple layer and complexation models.

We have also proposed a new set of constitutive equations to describe transport of ions and water in these clay-rich materials (Revil et al., 2005). This model was validated by a new set of experimental data made on the Callovo-Oxfordian argillite and to study diffusion of ions in bentonite (Leroy et al., 2006).

Acknowledgments. This work is supported by the French National Research Council (CNRS), the GDR-FORPRO, and the French National Agency for Radioactive Waste Management (ANDRA).

Few references

> Gaucher, E., C. Robelin, J. M. Matray, G. Negrel, Y. Gros, J. F. Heitz, A. Vinsot, H. Rebours, A. Cassabagnere, and A. Bouchet, ANDRA underground research laboratory: Interpretation of the mineralogical and geochemical data acquired in the Callovo-Oxfordian Formation by investigative drilling, Physics and Chemistry of the Earth, 29, 55-77, 2004.
> Gonçalves, J., S. Violette, and J. Wendling, Analytical and numerical solutions for alternative overpressuring processes: Application to the Callovo-Oxfordian sedimentary sequence in the Paris Basin, France, Journal of Geophysical Research, 109, B02110, doi:10.1029/2002JB002278, 2004.
> Leroy, P., and A. Revil, A triple-layer model of the surface electrochemical properties of clay minerals, Journal of Colloid and Interface Science, 270, 371-380, 2004.
> Leroy, P., A. Revil, and D. Coelho, Diffusion of ionic species in bentonite, Journal of Colloid and Interface Science, Volume 296, Issue 1, 248-255, 2006.
> Revil, A., Schwaeger, H., Cathles, L.M., and P. Manhardt, Streaming potential in porous media. 2. Theory and application to geothermal systems, Journal of Geophysical Research, 104(B9), 20,033-20,048, 1999.
> Revil, A., P. Leroy, and K. Titov, Characterization of transport properties of argillaceous sediments. Application to the Callovo-Oxfordian Argillite, Journal of Geophysical Research, 110, B06202, doi: 10.1029/2004JB003442, 2005.
> Revil, A., and N. Linde, Chemico-electromechanical coupling in microporous media, in press in Journal of Colloid and Interface Science.

Figure 1 (Click to enlarge)
Figure 1. a. Sketch of a natural argillite showing different porosity scales. b. Sketch of the electrical triple layer model at the surface of the clay minerals in the case of a binary monovalent electrolyte (NaCl here), M represents the metal cations (e.g., Na+) and A the anions (e.g., Cl-). OHP represents the Outer Helmholtz Plane, which coincides here with the shear plane along which the zeta potential is defined. The Beta-plane used in the main text is the plane of the Stern layer.



Figure 2 (Click to enlarge)
Figure 2. Pore size distribution of the Callovo-Oxfordian argillite (from ANDRA, 2005). The distinction between the macroporosity and the microporosity is based on the thickness of the diffuse layer.
The self-Potential method applied to contaminant sites

Co-Workers: T. Arora, N. Linde, J. Cstermant, and V. Naudet

Contaminant plumes that are rich in organic matter e.g., associated with leakage from municipal landfills, provide a source of electrical potential variations recordable at the Earth's surface. The contaminant plume can be regarded as a geobattery, in which the source current results from the degradation of the organic matter by the growth of micro-organisms and transport of electrons through nanowires that connect bacteria. These electrons are coming from the biodegradation of the organic matter by the bacteria.

Naturally electrical potential that can be recorded at the ground surface are termed self-potentials and they consist of two contributions. One contribution is associated with the flow of the water (streaming potential contribution) and the other contribution is associated with redox phenomena. To determine the redox potential from self-potential data, we need to remove the contribution associated with water flow.

Outside a contaminant plume located in the South of France, the hydraulic heads measured with a set of piezometers are highly correlated (R^2 = 0.90) to the self-potential signals. We used the kriging with external drift (KED) method to map the contribution of the streaming potential to the self-potential signals over the investigated area where we also incorporated the influence of the pore water conductivity upon the strength of the streaming potential signals. Then, we removed the streaming potential contribution from the measured self-potential signals, the residual self-potential data showed a good correlation (R^2 = 0.86 ) with the measured redox potentials in the aquifer with a slope close to 1/2. Finite element modelling demonstrates that this slope is consistent with our geobattery model.

Figure 1 (Click to enlarge) Figure 2 (Click to enlarge)
Figure 1. Self Potential map (in mV) of the data from Entressen Landfill. Black dots correspond to the 2800 self-potential measurements points made in the field along with the position of the piezometers for the chemical analyses and the measurement of the electrical conductivity of the groundwater. The piezometer #7 is located one kilometer upstream.
Figure 2. Map of the redox potential (in mV) (the small black circles represent the location of the self-potential data made in 2002 while the small black triangles represent the data obtained in 2006). The SP base station represents the reference station for the self-potential measurements (see Figure 1).
Few References

> Naudet, V., A. Revil, J.-Y. Bottero, and P. Bégassat, 2003. Relationship between self-potential (SP) signals and redox conditions in contaminated groundwater, Geophys. Res. Lett., 30(21), 2091, doi: 10.1029/2003GL018096.
> Naudet, V., A. Revil, E. Rizzo, J.-Y. Bottero, and P. Bégassat, 2004. Groundwater redox conditions and conductivity in a contaminant plume from geoelectrical investigations, Hydrology and Earth System Sciences, 8(1), 8-22.

Mechanical properties

Compaction of quartz sands by pressure solution using a Cole-Cole distribution of relaxation times

Co-workers : P. Leroy (1), A. Ghorbani (2), N. Florsch (2), and A.R Niemeijer (3)

(1) CNRS-CEREGE, University Paul Cézanne-Aix-Marseille III, Dept. of Hydrogeophysics and Porous Media, Aix-en-Provence, France (2) University Paris VI, Sisyphe, Paris, France. (3) HPT Laboratory, Faculty of Geosciences, Utrech University, Utrech, the Netherlands.

Pervasive pressure solution transfer (PPST) describes the irreversible compactional process of mass transfer in rocks in response to stress and temperature fluctuations. Other mechanism of deformation are possible like those associated with microcracking. PPST is associated with stress concentration at grain-to-grain contacts increasing solubility of the solid in the pore fluid, diffusion of the solute along grain-to-grain contacts, and precipitation on free faces of the grains. The understanding of PPST can lead to the understanding of locking / unlocking processes that affect granular gouge of active faults during the tectonic cycle (see recently Yasuhara et al., 2005) and compaction of quartz sands in sedimentary basins. In addition, PPST could explain soft creep rheology observed in the brittle-ductile transition zone of the crust and within the seimogeneic crust itself.

Stressed water-infiltrated silica rocks deform by pervasive pressure solution transfer (PPST), which involves dissolution of the grain-to-grain contacts, transport by diffusion of the solute, and precipitation on the free surfaces of the grains. A fundamental question regarding this process is how to model rheological behavior at stresses and temperatures typical of the crust of the Earth. The Voigt-type poro-visco-plastic model described by Revil (1999, 2001) has been modified by using a Cole-Cole distribution of relaxation times rather than a Dirac distribution used previously. The motivation of this choice was to account for the distribution of the grain size in the compaction of the porous aggregate assuming that this distribution obeys approximately a log normal distribution. This grain size distribution depends upon the initial grain size distribution and cataclasis in the early stage of compaction. We compared this modified visco-plastic model with the full set of experimental data obtained in various conditions of mean grain size, effective stress, and temperature by Niemeijer et al. (2002). These data provide tests of all aspects of the model, which can be considered to have no free parameters. We show the experiments of Niemeijer et al. (2002) on PPST are primarily diffusion-limited. The grain size distributions observed for three samples imply that the distribution of the relaxation time covers five orders of magnitude in grain size.

Acknowledgement. André Revil is grateful to the American Rock Mechanic Association (ARMA) for the 2004 Rock Mechanics Research Award he received and which has stimulated the present work. ANDRA is thanked for a grant given to P. Leroy during his Ph-D thesis. This paper is the GDR-FORPRO Contribution 2005/11A. D and is also a contribution from the project POLARIS (ANR-ECCO-PNRH).

111 Figure 1 (Click to enlarge)
Figure 1. Sketch of the compactional model.
a. The deformation of a representative elementary volume of quartz sand follows a linear poro-viscoplastic (Voigt-type) rheological behavior. The springs in parallel with the dashpot represent the plastic (thermostatic) equilibrium state, whereas the dashpots represent the kinetics of PPST at the grain-to-grain contacts (the dashpots "p" and "d" correspond to dissolution/ precipitation chemistry and diffusion limited processes, respectively) (modified from Revil, 2001). An additional spring models the poro-elastic response of the medium.
b. Analogy between a Voigt-type visco-plastic model (a dashpot in parallel with an anelastic spring) and an electrical circuit in which a resistor (R is the resistance) is in parallel with a capacitor (C is the capacitance). Such an electrical model is classically used to model the induced polarization response of water-saturated porous rocks.

Few References

> Niemeijer, A. R., and C. J. Spiers (2002), Compaction creep of quartz-muscovite mixtures at 500°C: Preliminary results on the influence of muscovite on pressure solution, in Deformation Mechanisms, Rheology and Tectonics: Current Status and Future Perspectives, edited by S. De Meer, M. R. Drury, J. H. P. De Bresser, and G. M. Pennock, London, Special Publications, Geological Society of London, 200, 61-71.
> Niemeijer, A. R., C. J. Spiers, and B. Bos (2002), Compaction creep of quartz sand at 400-600°C: experimental evidence for dissolution-controlled pressure solution, Earth Planetary Science Letters, 195, 261-275.
> Renard, F., P. Ortoleva, and J.P. Gratier (1997), Pressure solution in sandstones: influence of clays and dependence on temperature and stress, Tectonophysics, 280, 257-266.
> Revil, A. (2001), Pervasive pressure solution transfer in a quartz sand, Journal of Geophysical Research, 106(B5), 8665-8690.
> Revil, A. (1999), Pervasive pressure-solution transfer: a poro-visco-plastic model, Geophys. Res. Lett., 26, 255-258.
> Yang, X. S. (2000) Pressure solution in sedimentary basins: effect of temperature gradient, Earth Planet. Sci. Lett., 176, 233-243.
> Yang, X. S. (2002) A mathematical model for Voigt poro-visco-plastic deformation, Geophys. Res. Lett., 29(5),1066.
> Yasuhara, H., C. Marone, and D. Elsworth (2005), Fault zone restrengthening and frictional healing: the role of pressure solution, J. Geophys. Res., 110, B06310, doi: 10.1029/2004JB003327.
> Yasuhara, H., D. Elsworth, and A. Polak (2004), Evolution of permeability in a natural fracture: significant role of pressure solution, J. Geophys. Res., 109, B03204, doi: 10.1029/2003JB002663.
> Yasuhara, H., D. Elsworth, and A. Polak (2003), A mechanistic model for compaction of granular aggregates moderated by pressure solution, J. Geophys. Res., 108(B11), 2530, doi: 10.1029/2003JB002536.

Figure 2 (Click to enlarge)
Figure 2.
a. Compaction curve of a quartz aggregate in the initial stage of deformation. Data from Niemeijer et al. (2002) (Run Cpf8, Effective pressure: 100 MPa, mean grain diameter: 12 micro.m, effective stress 100 MPa, temperature 500°C, Phi(i)= 0.311).
b. Comparison between the predicted porosity and the measured porosity.
c. Comparison between the measured grain size distribution and that predited using the Cole-Cole distribution (plain line).

Streaming potentials of granular media. Influence of the Reynolds number

Co-workers: A. Bolève (1, 2), A. Crespy (1), F. Janod (2), and J. L. Mattiuzzo (2)

(1) CNRS-CEREGE, Université Paul Cézanne, Département d'Hydrogéophysique et Milieux Poreux, Aix-en-Provence, France. (2) SOBESOL, Savoie Technolac, BP 230, F-73375 Le Bourget du Lac Cedex, France

The generation of electrical signals associated with the movement of water in porous/fractured materials is related to the drag of the excess of charge contained in the pore water of the porous medium (e.g., Bull and Gortner, 1932). The record of these electrical fields provides a powerful geophysical method to track the pattern of ground water flow. Indeed, applications in geohydrology concern the forced movement of water associated with deformation of porous rocks (e.g., Lorne et al., 1999a, b; Revil et al., 2003), the determination of preferential flow paths over karstic areas (Jardani et al., 2006), the determination of transmissive properties of unconfined aquifers (Titov et al., 2000), the determination of subglacial flow pattern (Kulessa et al., 2003a, b), CO2 sequestration (Moore et al., 2004), and the detection of leakages in embankments dams and the interpretation of the resulting self-potential signals in terms of seepage velocity (e.g., Bogoslovsky and Ogilvy, 1970; Gex, 1980; Panthulu et al., 2001; Sheffer, 2002; Sheffer and Howie, 2001, 2003; Titov et al., 2005; Rozycki et al., 2006). These works have also recently driven the development of new algorithms of self-potential tomography (e.g., Revil et al. 2001; Long and Hao, 2005) and tank scale laboratory measurements in well-controlled conditions to check the underlying physics of these processes (Maineult et al., 2005, 2006). Similar types of analysis were carried out recently in medical imaging to study the flow of electrolytes in cartilage submitted to mechanical loads (Sachs and Grodzinsky, 1995; Garon et al., 2002) and in plant sciences to monitor the sap flow in trees (Gibert et al., 2006).

There are a number of works published in the literature regarding the measurement of the streaming potentials associated with the flow of the water through granular porous materials (e.g., Lorne et al., 1999a, b). For example, Bull and Gortner (1932) shows a decrease by two orders of magnitude of the strength of the streaming potentials when the grain size decreases by two orders of magnitude from ~5 to 500 mm at low ionic strengths (10-4 and 2x10-4 N, NaCl at 25°C). This decrease was explained by Revil et al. (1999b) as resulting from the influence of the surface conductivity of the grains.

Figure 1 (Click to enlarge)
Figure 1. Influence of the Reynolds number, determined from Eqs. (22) and (23), upon the relative coupling coefficient C/C0 (where C is the measured apparent streaming potential coupling coefficient and C0 is given by Eq. (15)) and the relative permeability k/k0 (where k is the measured apparent permeability (using Darcy's law) and k0 is given by Eq. (8)). These measurements have been realized at different salinities showing the universal character of this trend.

However, very few researchers have investigated the effect of non-viscous laminar flow upon the electrokinetic process. Streaming potential measurements were realized in capillaries of different radii to see the influence of the viscous sublayer upon the electrokinetic process at high Reynolds numbers (Bocquet et al., 1956; Kurtz et al., 1976). However, as far as we know, there were no works investigating quantitatively the influence of the Reynolds number upon the value of the streaming potential coupling coefficient at the transition between the viscous-laminar flow regime and the inertial-laminar flow regime.

In this paper, we propose a new formulation regarding the influence of the Reynolds number upon the coupled hydroelectric problem of porous material. In this formulation, we also account for the influence of surface conductivity. To check the validity of this model, we measure the streaming potential coupling coefficient and electrical conductivity of glass bead packs at different salinities. We investigate a set of seven well-calibrated glass bead packs that can be considered as a standard material for the investigation of electrokinetic phenomena. The mean grain size of the samples is in the range 56 to 3000 mm (the permeability of these samples covers approximately four orders of magnitude and the porosity is approximately that of a random packing of spherical particles f = 0.40). We used NaCl solutions with electrical conductivity in the range 10-1 to 10-4 S m-1 at 25°C that corresponds to the conductivity of the surface and ground waters often meet in hydrology. Our goal in this paper is to provide a model explaining the variations of the streaming potentials coupling coefficient with the mean grain diameter of the sample at different salinities.

Acknowledgments. This work is supported by ANR Project ERINOH in France related to the study of leakages in embankments dams and ANR-ECCO-PNRH Project POLARIS. The Ph-D Thesis of A. Bolève is supported by SOBESOL and the Ph-D thesis of Agnès Crespy by the Ministère de la Recherche et de l’Enseignement in France.

Few references

> Bogoslovsky, V.A., and V.A. Ogilvy (1970), Natural potential anomalies as a quantitative index of the role of water seepage from reservoir, Geophysical Prospecting, 18, 261-268.
> Bull, H.B., and R.A. Gortner (1932), Electrokinetic potentials. X. The effect of particle size on potentials, J. Phys. Chem., 36, 111-119.
> Gex, P. (1980), Electrofiltration phenomena associated with several dam sites, Bulletin of the Society Vaud Science and Nature, 357(75), 39-50.
> Gorelik, L.V. (2004), Investigation of dynamic streaming potential by dimensional analysis, J. Colloid and Interface Science, 274, 695-700.
> Moore, J.R., S.D. Glaser, H.F. Morrison, and G.M. Hoversten (2004), The streaming potential of liquid carbone dioxide in Berea sandstone, Geophys. Res. Lett., 31(17), L17610, 2004.
> Revil, A. and N. Linde (2006), Chemico-electromechanical coupling in microporous media, in press in Journal of Colloid and Interface Science.
> Revil, A., P. Leroy, and K. Titov (2005), Characterization of transport properties of argillaceous sediments. Application to the Callovo-Oxfordian Argillite, J. Geophys. Res., 110, B06202, doi: 10.1029/2004JB003442.
> Revil, A., and P. Leroy (2001), Hydroelectric coupling in a clayey material, Geophysical Research Letters, 28(8), 1643-1646.
> Revil, A. (2002), The hydroelectric problem of porous rocks: thermodynamic approach and introduction of a percolation threshold, Geophysical Journal International, 151(3), 944-949.
> Rozycki, A., J.M.R. Fonticiella, and A. Cuadra (2006), Detection and evaluation of horizontal fractures in Earth dams using self-potential method, Engineering Geology, 82(3), 145-153.
> Sheffer, M.R. (2002), Response of the self-potential method to changing seepage conditions in embankments dams, M.A.Sc. Thesis, Dept. of Civil Eng., University of British Columbia, April 2002.
> Sheffer, M.R., and J.A. Howie (2001), Imaging subsurface seepage conditions through the modeling of streaming potential, Proceedings of 54th Canadian Geotechnical Conference, Calgary, P. 1094-1101.

Volcanology and Geothermal Systems
Hydrogeological insights at Stromboli volcano (Italy) from geoelectrical, temperature, and CO2 soil degassing investigations

Co-Workers: A. Finizola (1,2), E. Rizzo (4), S. Piscitelli (4), T. Ricci (5), J. Morin (6, 2), B. Angeletti (3), L. Mocochain (3), and F. Sortino (1)

(1) Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Italy. (2) Now at Laboratoire des Sciences de la Terre de l'Université de la Réunion (LSTUR), Institut de Physique du Globe de Paris, CNRS, UMR 7154, Saint Denis, La Réunion, France. (3) CNRS-CEREGE, Université Aix-Marseille III, Aix-en-Provence, France. (4) IMAA-CNR, Potenza, Italy. (5) Università Roma Tre, Roma, Italy. (6) Université de la Sorbonne, Paris, France.

Located in the northern part of the Aeolian arc (Tyrrhenian Sea), Stromboli rises to 924 meters above the sea level and its base lies at a depth of ~2 km on the sea-floor (Figure 1). This volcano is characterized by a persistent rhythmic activity, for more than one millennium (Rosi et al., 2000). This activity is sometimes disrupted by paroxysmal events (e.g., Barberi et al. 1993).
These paroxysms are related to interaction between the magmatic column and water bodies present in the central part of the edifice (Rittmann, 1931), like during the event of April, 5th 2003. It is not clear however if phreato-magmatic processes were the origin, or a consequence, of these paroxysms. For these reasons, Stromboli appears as an suitable natural laboratory to test the capacity of geoelectrical methods to monitor volcanic activity (Finizola et al., 2002, 2003; Revil et al., 2004b).

Finding the geometry of aquifers in an active volcano is important for evaluating the hazards associated with phreato-magmatic phenomena and incidentally to address the problem of water supply. A combination of electrical resistivity tomography (ERT), self-potential, CO2, and temperature measurements provides insights about the location and pattern of ground water flow at Stromboli volcano (Figure 2). The measurements were conducted along a NE-SW profile across the island from Scari to Ginostra, crossing the summit (Pizzo) area. ERT data (electrode spacing 20 m, depth of penetration of ~200 m) shows the shallow architecture through the distribution of the resistivities. The hydrothermal system is characterized by low values of the resistivity (< 50 ohm.m) while the surrounding rocks are resistive (> 2000 ohm.m) except on the North-East flank of the volcano where a cold aquifer is detected at a depth of ~80 m (resistivity in the range 70-300 ohm.m). CO2 and temperature measurements corroborate the delineation of the hydrothermal body in the summit part of the volcano while a negative self-potential anomaly underlines the position of the cold aquifer.

Acknowledgments: The INSU-CNRS, the CNR, and the Istituto Nazionale di Geofisica e Vulcanologia (INGV) are thanked for financial supports.

Related References

> Allard, P., Carbonnelle, J., Metrich, N., Loyer, H., Zettwoog, P. (1994). Sulphur output and magma degassing budget of Stromboli volcano. Nature, 368, 6469, 326-330.
> Barberi, F., M. Rosi, and A. Sodi (1993). Volcanic hazard assessment at Stromboli based on review of historical data. Acta Vulcanologica, 3, 173-187.
> Chiodini, G., R. Cioni, M. Guidi, L. Marini, and B. Raco (1998). Soil CO2 flux measurements in volcanic and geothermal areas. Appl. Geochem., 13, 543-552.
> Finizola, A., S. Sortino, J.-F. Lénat, M. Aubert, M. Ripepe, and M. Valenza (2003). The summit hydrothermal system of Stromboli. New insights from self-potential, temperature, CO2 and fumarolic fluid measurements. Structural and monitoring implications, Bull. Volcanol., 65, 486-504, doi:10.1007/s00445-003-0276-z.
> Finizola, A., S. Sortino, J.-F. Lénat and M. Valenza (2002). Fluid circulation at Stromboli volcano (Aeolian Islands, Italy) from self-potential and CO2 surveys, J. Volcanol. Geotherm. Res., 116, 1-18.
> Hornig-Kjarsgaard, I., J. Keller, U. Koberski, E. Stadlbauer, L. Francalanci, and R. Lenhart (1993). Geology, stratigraphy and volcanological evolution of the island of Stromboli, Aeolian arc, Italy, Acta Vulcanologica, 3, 21-68.
> Keller, J., I. Hornig-Kjarsgaard, U. Koberski, E. Stadlbauer, and R. Lenhart (1993). Geological map of the island of Stromboli. Acta Vulcanol., 3.
> Loke, M.H. and R. D. Barker (1996). Rapid least-squares inversion of apparent resistivity pseudosections by a quasi-Newton method, Geophysical Prospecting, 44, 131-152.
> Nappi, G., B. Capaccioni, F. Biagiotti, and O. Vaselli (1999). Upper pyroclastic sequenze of the Scari formation: a paroxistic eruption from Stromboli volcano (Aeolian Island, Italy), Acta Vulcanologica, 11(2), 259-264.
> Revil, A., V. Naudet, and J. D. Meunier (2004a). The hydroelectric problem of porous rocks: Inversion of the water table from self-potential data, Geophysical J. International, 159, 435-444.
> Revil, A., A. Finizola, F. Sortino, and M. Ripepe (2004b). Geophysical investigations at Stromboli volcano, Italy. Implications for ground water flow, Geophysical J. International, 157, 426-440.
> Rittmann, A., (1931). Der Ausbruch des Stromboli am 11 september 1930, Zeits. Vulkanol., 14, 47-77.
> Rosi, M., A. Bertagnini, and P. Landi (2000). Onset of the persistent activity at Stromboli volcano (Italy). Bull. Volcanol., 62, 294-300.

Figure 1 (Click to enlarge)
Figure 1. Geological map of Stromboli volcano showing the seven stages constituting the evolution of the edifice (modified from Keller et al., 1993). The yellow line corresponds to the location of the resistivity profile. PST stands for Paleostromboli (*): from Keller et al., 1993; (**): from Finizola et al., 2002; (***): from Nappi et al., 1999.
Figure 2 (Click to enlarge)
Figure 2. Temperature, self-potential, CO2 measurements made along the electrical resistivity profile crossing the entire Stromboli island, along a NE-SW direction. "C" and "R" stand for the conductive and resistive bodies discussed in the text.