The presence of residual subduction zone under Kuril island arc makes a region of Kuril ridge islands be potential seismic-danger since underwater earthquakes in subduction zone with magnitude М > 6 are usually tsunamigenic. Potential strong earthquakes near the Kuril-Kamchatka trench passes along Kuril island, and tsunami generated by them carry a greater risk while passing through Bussol and Krusenstern straits for all Okhotsk seashore including the Sakhalin coast where now taking place a rising of infrastructure development connected with development an oil and gas industry. In the history, a few occasions of tsunami generation near the Sakhalin coast, caused by earthquakes in Kuril ridge region had been recorded (see, e.g. [1]). Such occasion taken place while strongest earthquake occurs recently near the Simushir island (15 November 2006). This earthquake and tsunami were predicted half of year before the event: while marine expedition clarified structure and size of possible undersea source in the area of seismic gap in Middle Kuril region. Then, the numericalsimulation of tsunami generation and propagation was performed using keyboard model of an earthquake. Since not all seismic gap area was activated, it’s interesting to perform a numerical modeling of potential catastrophic earthquake and tsunami in residual seismic gap of Middle Kuril and compare results with similar scenario of earthquake and tsunami for hypothetical source placed in inactive part of seismic gap. In this paper, such modeling was performed based on keyboard model of tsunamigenic earthquakes [2]. Calculation was performed using nonlinear shallow water equations and considering bottom dissipation. Spectral analysis of tsunami wave field in this model gives new possibilities for determination of energy characteristics of tsunami in the whole modeling area.