The following four drawings show what level of blast damage (at different psi overpressure) and fire ignition from the thermal pulse might be expected for different strength nuclear explosions (both ground and air bursts) at different distances from ground zero. Take note of the damage range distances from GZ - ground zero. (Courtesy of Nuclear Attack Environment Handbook, FEMA - August, 1990)
Obviously, the bigger the weapon yield the larger the area of overpressure damage from the blast wave. But, notice that the damage range does not increase in a linear fashion with the more powerful explosions. For instance, comparing the 200 KT air burst with the five times more powerful 1 MT air burst, the range of moderate damage and initial fires increased from only 4.3 miles to 7.3 miles. This is because the reach of blast and fire effects varies as the cube root of the weapon yield ratio and the cube root of 5 is 1.71. So, instead of a five-fold increase or 500% we have only about a 70% increase in this comparison.
A readily portable terrorist nuclear bomb would likely be only a fraction as powerful as the examples above, but for reference, the Hiroshima nuclear bomb was only a 15KT air burst. (The RA-115 backpack nukes reported missing from Russian stockpiles are one kiloton yield each, and they would most likely be surface exploded.)
I should probably keep my mouth shut because everybody needs a reason to try to survive, and most people will survive the initial attack. However, if youre within a short distance of a large body of water like Chicago and Lake Michigan or cities around the Gulf of Mexico (or New York or LA), you can forget it.
The terrorists dont need to place a bomb on the top of the Sears Tower (which is well guarded), but instead place it on the bottom of the lake (or Gulf or whatever) which cant be guarded. Draining the lake (or whatever) insures a much higher kill ratio than a ground or air burst and bomb shelters only make it convenient to find the bodies once the water recedes.
Citizens of Chicago, LA, New York, go ahead and vote for appeasers, it takes about 4-5 minutes to drown, you can repent your sins during that time.
If anybody thinks that Im giving the enemy ideas, my dad (a certified nuclear shelter inspector) told me about this in the early 60s. Thats the reason our family never lived near a large body of water.
When I talk to people about this subject they invariably ask me what provisions that I have to survive. I tell them that I have a good battle rifle. They always say that thats nice but what will I eat? I just ask them what do you have? It takes a minute or two, but you can tell when they understand.