Abstract: An intra-crustal M_W8.8 strong earthquake occurred off the eastern coast of Kamchatka, triggering a tsunami and attracting global attention. Some researchers have analyzed the mechanical mechanism of this strong earthquake from the stress field. We utilizes our previous results via seismic tomography to analyze the relationship between the velocity structure and this strong earthquake according to the seismic wave velocity, and compares it with the 2011 Japan earthquake to discuss the triggering effect of deep fluids on the M_W 8.8 earthquake.