Four sandbox experiments were performed to understand the self-potential
response to hydro-mechanical disturbances in a water-infiltrated
controlled sandbox. In the first two experiments, similar to 0.5 mL of
water was abruptly injected through a small capillary at a depth of 15
cm using a syringe impacted by a hammer stroke. In the second series of
experiments, similar to 0.5 mL of pore water was quickly pumped out of
the tank, at the same depth, using a syringe. In both type of
experiments, the resulting self-potential signals were measured using 32
sintered Ag/AgCl medical electrodes. In two experiments, these
electrodes were located 3 cm below the top surface of the tank. In two
other experiments, they were placed along a vertical section crossing
the position of the capillary. These electrodes were connected to a
voltmeter with a sensitivity of 0.1 mu V and an acquisition frequency of
1.024 kHz. The injected/pumped volumes of water produced
hydro-mechanical disturbances in the sandbox. In turn, these
disturbances generated dipolar electrical anomalies of electrokinetic
nature with an amplitude of few microvolts. The source function is the
product of the dipolar Green's function by a source intensity function
that depends solely on the product of the streaming potential coupling
coefficient of the sand to the pore fluid overpressure with respect to
the hydrostatic pressure. Numerical modeling using a finite element code
was performed to solve the coupled hydro-mechanical problem and to
determine the distribution of the resulting self-potential during the
course of these experiments. We use 2D and 3D algorithms based on the
cross-correlation method and wavelet analysis of potential fields to
show that the source was a vertical dipole. These methods were also used
to localize the position of the source of the hydromechanical
disturbance from the self-potential signals recorded at the top surface
of the tank. The position of the source agrees with the position of the
inlet/outlet of the capillary showing the usefulness of these methods
for application to active volcanoes.