The dynamics of the velocity field beneath the North group of volcanoes,Kamchatka, and its relationship to the evolution of volcanic activity

P- and S-wave travel times from local volcanic earthquakes recorded in the North group of volcanoes area during the 2005–2009 period were treated by the “reverse wave” method to calculate the V _P velocity field and the TAU parameter, which is an analogue of the P- to S-wave velocity ratio. We constructed 3D velocity distributions along the line traversing the volcanic group along the direction from Ploskii Tolbachik Volcano in the southwest toward Shiveluch Volcano in the northeast. Dynamic changes in the velocity field were identified, both over time and depth. We examine the relationships of these dynamic changes to the evolution of volcanic activity during the period indicated.