SP Coseismic Signals observed on an electrodes array in an underground quarry

Electric self-potentials (SP) and strains were measured on the surface of a pillar of the abandoned underground Meriel limestone quarry (France). The time variations of strains and SP are interpreted in terms of crack instabi lity. The dynamic mapping technique shows that the most intensive SP variat ions, corresponding to maximum stress variations estimated from strain data , occur in the vicinity of active crack tips or crack intersections. The lo cation of these maxims changes with the stress distribution variations. The synchronous stacking technique allows to detect:significant pressure varia tions through electrodes installed in the fractured zone as well as through outside electrodes close to the medium discontinuities (petrological bound aries and pillar edges).