Subsurface injection of fluids inside tectonically active areas is in some cases followed by a seismic response. This paper examines an example of seismic activation on the northeast coast of Sakhalin Island (in the area of the North American tectonic plate) in 2013–2014, which coincides with the start of the pilot operation of injection wells designated for the disposal of drilling fluids and co-produced and domestic wastewater from nearby oil and gas operations. Hypothesizing that the recorded seismicity is entirely induced by the fluid disposal, and considering injection rates of 10 5 m 3 /year, we estimate a seismogenic index of Σ =  −3.98 ± 0.06. Assuming a total injection volume of V C  = 10 7 m 3 until 2041, the probability of occurrence of at least one earthquake with a magnitude M 5.5 was calculated to be P E  = 0.99. The obtained results are of practical interest for developing seismic risk management strategies and using numerical tools to quantify seismic hazards.