Well seabed pressure(?)/hydrostatic pressure/atmospheric pressure have always been with us. In the overall scheme of things, any effect of variations in them that might impact on the earth's crust, in which severe earthquakes usually happen at great depths, is minuscule. So the null hypothesis is that, as there is no evidence for those phenomena being causes for major earthquakes, they have little or no effect on seismic phenomena. Science can go no further without your evidence to the contrary. You have precious little such evidence, and just a reminder that speculation and flights of the imagination are not evidence.