How “big” or “huge” the effects of a 7.0 are is depends on more than just the original energy released. Depth of the quake has already been mentioned, and duration also counts. Other major factors are how efficiently the shock waves are transmitted (the largest of the New Madrid quakes in 1811-1812 reputedly rang church bells in New England!), and whether the soil(s) liquify (which was also devastating in the New Madrid quakes.) The New Madrid quakes of 1811-12 were much larger, of course, but even a 7.0 there any time in the near future could largely destroy some of the nearby towns.
How “big” or “huge” the effects of a 7.0 are depends on...
(So much for my initial proofread!)