First laboratory measurements of seismo‐magnetic conversions in fluid‐filled Fontainebleau sand

[1] Seismic wave propagation in fluid-filled porous materials induces electromagnetic effects due to small relative pore-fluid motions. In order to detect the seismo-magnetic couplings theoretically predicted by Pride (1994), we have designed a small-scale experiment in a low-noise underground laboratory which presents exceptional electromagnetic shielding conditions. Our experiment included accelerometers, electric dipoles and induction magnetometers to characterize the seismo-electromagnetic propagation phenomena. To assess the electrokinetic origin of the measured electric and magnetic fields, we compared records obtained in dry and fluid-filled sand. Extra care has been taken to ensure the mechanical decoupling between the sand column and the magnetometers to avoid spurious vibrations of the magnetometers and misinterpretations of the recorded signals. Our results show that seismo-electric and seismo-magnetic signals are associated with different wave propagation modes, thus emphasizing the electrokinetic origin of these effects.

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

[2]  Rosemary Knight,et al.  A laboratory study of the dependence of elastic wave velocities on pore scale fluid distribution , 1990 .

[3]  M. Nafi Toksöz,et al.  Seismoelectric and seismomagnetic measurements in fractured borehole models , 2005 .

[4]  Stéphane Garambois,et al.  Full waveform numerical simulations of seismoelectromagnetic wave conversions in fluid‐saturated stratified porous media , 2002 .

[5]  Laurence Jouniaux,et al.  Streaming potential of a sand column in partial saturation conditions , 2003 .

[6]  A. H. Thompson,et al.  Geophysical applications of electrokinetic conversion , 1993 .

[7]  M. Nafi Toksöz,et al.  Using borehole electroseismic measurements to detect and characterize fractured (permeable) zones , 2000 .

[8]  Steven R. Pride,et al.  Electroseismic wave properties , 1996 .

[9]  Nobunao Takeuchi,et al.  Observations of earthquake waves by the vertical earth potential difference method , 1997 .

[10]  Stéphane Garambois,et al.  Seismoelectric wave conversions in porous media: Field measurements and transfer function analysis , 2001 .

[11]  Steven R. Pride,et al.  Electroseismic waves from point sources in layered media , 1997 .

[12]  S. Kelly,et al.  Theory of Propagation of Elastic Waves in a Fluid-Saturated Porous Solid , 1956 .

[13]  Benjamin S. White,et al.  Asymptotic Theory of Electroseismic Prospecting , 2005, SIAM J. Appl. Math..

[14]  M. Nafi Toksöz,et al.  Seismoelectric and seismomagnetic measurements in fractured borehole models , 2005 .

[15]  M. N. Toksöz,et al.  Experimental studies of seismoelectric conversions in fluid-saturated porous media , 2000 .

[16]  S. T. Martner,et al.  THE ELECTROSEISMIC EFFECT , 1959 .

[17]  Jean Virieux,et al.  Simultaneous seismic and magnetic measurements in the Low-Noise Underground Laboratory (LSBB) of Rustrel, France, during the 2001 January 26 Indian earthquake , 2003 .