Improvements in Seismoelectric Acquisitions at Field and Lab Scales and Records Interpretation

Tackling the subject of seismoelectric investigations first at field then at lab scale, we have repeatedly been confronted with the pervasive and challenging issue of noise reduction. In our case, noise can take different forms, being either environmental or internal, last being not least. Thus, we developed our laboratory setup introducing five levels of shielding at the seismic source and choosing differential over single-ended transmission. On this basis, we were eventually capable to reduce the internal noise due to the operating seismic source by 4 orders of magnitudes. This enabled a clear record of the coseismic electric field as well as the observation of flat events distinct from the source pulse not yet totally removed, which amplitudes and arrival times proved consistent with an interfacial converted response. In the field, after having forced us to trigger manually, triggering noise was finally remedied by using optical fiber as triggering cable, thus reducing the pre-processing time tremendously. Being ridden of plaguing noise sources, we are now free to conduct systematic studies in both field and lab as well as to address the issue of environmental noise reduction using numerical filtering.