Even that doesn't tell the "whole story." The largest effect ring was the "thermal radiation" one. This would be the effect of direct radiant heat, but the "dirty" effect of ionizing radiation, which can cause delayed radiation effects such as cancer, etc., goes much further, depending on the prevailing wind patterns, etc. Though the blast range may not reach Oxford from a 100 MT blast in Memphis, depending on the wind patterns, a far larger area could be contaminated, and potentially evacuated--possibly for years. Fortunately, the "dirty" yield of hydrogen bombs (fusion) is far less than that of large fission nukes, because it is only the nuclear fission "trigger" that yields the radiation effect. The fusion blast is far more powerful, but "cleaner." A neutron bomb, has very little (relative) blast effect, but kills by penetrating radiation, sparing the buildings, but frying organic matter.
