The volcano‐electric effect

[1] The formation of a magmatic intrusion at depth is responsible for the formation of various thermohydromechanical (THM) disturbances including the upsurge of shock waves and diffusion of pressure fronts in the volcanic system. We couple electromagnetic theory (Maxwell equations) and thermoporoelasticity (Biot equations) to look at the ground surface electrical signature of these THM disturbances. The nature of this coupling is electrokinetic, i.e., associated with water flow relative to the mineral framework and the drag of the excess of charge located in the vicinity of the pore water/mineral interface (the groundwater flow disturbance being related here to the THM disturbances in drained conditions). A new set of laboratory data shows that the electrokinetic coupling is very substantial in fractured basaltic and volcaniclastic materials, and in scoria with several hundreds of millivolts of electrical potential gradient produced per megapascal of pore fluid pressure variations. Our theoretical analysis predicts the diffusion of electromagnetic disturbances and quasi-static electrical signals. These signals can be used as precursors of a volcanic eruption. Indeed, electromagnetic phenomena recorded at the ground surface of a volcanic system, once properly filtered to remove external contributions, provide a direct and quasi-instantaneous insight into the THM disturbances occurring in the heart of the volcanic structure prior and during a volcanic event. Tomography of the quasi-static electrical field is discussed and applied to self-potential profiles performed at the Piton de la Fournaise volcano during the preparation phase of the March 1998 eruption.

[1]  R. Büttner,et al.  Short‐time electrical effects during volcanic eruption: Experiments and field measurements , 2000 .

[2]  R. Schultz.  Limits on strength and deformation properties of jointed basaltic rock masses , 1995 .

[3]  Pascal Sailhac,et al.  Analytic potentials for the forward and inverse modeling of SP anomalies caused by subsurface fluid flow , 2001 .

[4]  Dominique Gibert,et al.  Identification of sources of potential fields with the continuous wavelet transform: Application to self‐potential profiles , 2001 .

[5]  André Revil,et al.  Streaming potential in porous media: 2. Theory and application to geothermal systems , 1999 .

[6]  P. Mauriello,et al.  Electric and electromagnetic outline of the Mount Somma–Vesuvius structural setting , 1998 .

[7]  D. Patella.  Introduction to ground surface self‐potential tomography , 1997 .

[8]  P. Domenico,et al.  Fluid pressures in deforming porous rocks , 1989 .

[9]  A. Revil.  The hydroelectric problem of porous rocks: thermodynamic approach and introduction of a percolation threshold , 2002 .

[10]  J. Avouac,et al.  Streaming potential measurements 1. Properties of the electrical double layer from crushed rock samples , 1999 .

[11]  M. Toksöz,et al.  Dynamic streaming currents from seismic point sources in homogeneous poroelastic media , 1998 .

[12]  J. Zlotnicki,et al.  Volcanomagnetic effects observed on Piton de la Fournaise Volcano (Réunion Island): 1985–1987 , 1988 .

[13]  T. Hashimoto,et al.  A large self-potential anomaly on Unzen Volcano, Shimabara Peninsula, Kyushu Island, Japan , 1995 .

[14]  A. Revil,et al.  Hydroelectric coupling in a clayey material , 2001 .

[15]  J. Lenat,et al.  Le Piton de la Fournaise , 1993 .

[16]  Shingo Yoshida,et al.  Convection current generated prior to rupture in saturated rocks , 2001 .

[17]  Volcanomagnetic Effect Observed during the 1986 Eruption of Izu-Oshima Volcano , 1990 .

[18]  L. Jouniaux,et al.  Constraints on hydrothermal processes on basaltic edifices: inferences on the conditions leading to hydrovolcanic eruptions at Piton de la Fournaise, Réunion Island, Indian Ocean , 2001 .

[19]  Yoshikazu Tanaka.  Eruption mechanism as inferred from geomagnetic changes with special attention to the 1989–1990 activity of Aso volcano , 1993 .

[20]  G. Natale,et al.  Rock deformation and fracturing processes due to nonlinear shock waves propagating in hyperthermal fluid pressurized domains , 1998 .

[21]  G. Petiau.  Second Generation of Lead-lead Chloride Electrodes for Geophysical Applications , 2000 .

[22]  C. Negro,et al.  Retrieval of large volcanomagnetic effects observed during the 1981 eruption of Mt.Etna , 1997 .

[23]  David V. Fitterman,et al.  Electrokinetic and magnetic anomalies associated with dilatant regions in a layered Earth , 1978 .

[24]  Fracturing processes due to temperature and pressure nonlinear waves propagating in fluid‐saturated porous rocks , 2001 .

[25]  A. Revil,et al.  Tomography of self‐potential anomalies of electrochemical nature , 2001 .

[26]  Claude Fournier,et al.  Spontaneous potentials and resistivity surveys applied to hydrogeology in a volcanic area: case history of the Chaîne des Puys (Puy-de-Dôme, France) , 1989 .

[27]  N. Matsumoto,et al.  Hydrological anomalies associated with crustal deformation before the 2000 eruption of Usu volcano, Japan , 2002 .

[28]  J. Lenat,et al.  Cartographie et surveillance temporelle des anomalies de polarisation spontanee (PS) sur le Piton de la Fournaise , 1994 .

[29]  André Revil,et al.  Self‐potential signals associated with variations of the hydraulic head during an infiltration experiment , 2002 .

[30]  J. Avouac,et al.  Radon emanation and electric potential variations associated with transient deformation near reservoir lakes , 1999, Nature.

[31]  M. Johnston,et al.  Rapid fluid disruption: A source for self‐potential anomalies on volcanoes , 2001 .

[32]  T. Ishido,et al.  Experimental and theoretical basis of electrokinetic phenomena in rock‐water systems and its applications to geophysics , 1981 .

[33]  A. Revil,et al.  Electrical properties of zeolitized volcaniclastic materials , 2002 .

[34]  D. F. McTigue,et al.  Thermoelastic response of fluid‐saturated porous rock , 1986 .

[35]  G. Natale,et al.  Subsurface propagation of thermomechanical kinks through hydrothermal fluid-saturated porous horizons , 1999 .

[36]  A. Revil.  Genesis of mud volcanoes in sedimentary basins: A solitary wave‐based mechanism , 2002 .

[37]  Pride,et al.  Governing equations for the coupled electromagnetics and acoustics of porous media. , 1994, Physical review. B, Condensed matter.

[38]  G. Natale.  The Effect of Fluid Thermal Expansivity on Thermo-mechanical Solitary Shock Waves in the Underground of Volcanic Domains , 1998 .

[39]  J. Lénat,et al.  Geoelectrical structure of the central zone of Piton de la Fournaise volcano (Réunion) , 2000 .

[40]  A. Revil.  Comment on ''Rapid fluid disruption: A source for self-potential anomalies on volcanoes'' by M. J. S. Johnston, J. D. Byerlee, , 2002 .

[41]  Schwartz,et al.  Fluid permeability in porous media: Comparison of electrical estimates with hydrodynamical calculations. , 1992, Physical review. B, Condensed matter.

[42]  Y. Bernabé.  Streaming potential in heterogeneous networks , 1998 .

[43]  M. Johnston,et al.  Volcano‐magnetic effect observed on Mt. Ruapehu, New Zealand , 1969 .

[44]  J. Zlotnicki,et al.  Self-potential and magnetic surveying of La Fournaise volcano (Réunion Island): Correlations with faulting, fluid circulation, and eruption , 1998 .

[45]  Bezalel C. Haimson,et al.  Hydrofracturing stress measurements in the Iceland Research Drilling Project drill hole at Reydarfjordur, Iceland , 1982 .