A micro-seismic survey was carried out in concurrence with reservoir interference tests around Olkaria well 719, which has a mass output of 140-160 ton/h. The correlation between output and micro-seismicity shows that the seismic intensity peaks have a time lag of 6 to 11 days behind the mass output peaks. Seismicity spreads from the well bore in two major directions, a faster NE-SW trend at about 0.6 m/h and a slow NW-SE trend at about 0.4 m/h. These rates are comparable to those obtained by injecting organic tracers and monitoring in adjacent wells. Fluid feeder zones are at 1300-1400 m and 1600-1800 m depth and are coincident with contacts between different lithologies that provide capping and horizontal permeability. A possible NNE-SSW trending barrier to fluid flow has been observed between OW-719 and OW-718 wells.