North Korea's Nuclear Tests 2006 to present

2006 less than one kiloton detonated underground
2009 2 kilotons detonated underground
2013 6-7 kilotons detonated underground
January 2016 4-6 kilotons detonated underground
September 2016-  10 kilotons detonated underground

These facts are from CNN Wolf Program at 10 am pacific time January 2nd 2017

So, my question might be: "What kind of damage would 10 kilotons do if strapped to a North Korean ICBM?

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1. Nuclear weapon - Wikipedia

   www.wikipedia.org/search-redirect.php?family=...

   Nuclear weapons delivery—the technology and systems used to bring a nuclear weapon to its target—is an important aspect of nuclear weapons relating both to ...

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion (thermonuclear weapon). Both reactions release vast quantities of energy from relatively small amounts of matter. The first test of a fission ("atomic") bomb released the same amount of energy as approximately 20,000 tons of TNT (84 TJ). The first thermonuclear ("hydrogen") bomb test released the same amount of energy as approximately 10 million tons of TNT (42 PJ).
A thermonuclear weapon weighing little more than 2,400 pounds (1,100 kg) can produce an explosive force comparable to the detonation of more than 1.2 million tons of TNT (5.0 PJ).^[1] A nuclear device no larger than traditional bombs can devastate an entire city by blast, fire, and radiation. Nuclear weapons are considered weapons of mass destruction, and their use and control have been a major focus of international relations policy since their debut.

Therefore 20,000 tons of TNT I suppose would be a 20 kiloton weapon? So, 2,400 pounds or 1,100 kg produces the same as 1.2 milion tons of TNT.

Also, the only presently known detonations of nuclear weapons on cities with people in them is Hiroshima and Nagasaki. here is what wikipedia says about this:

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atomic bombings of Hiroshima and Nagasaki
 
By August 1945, the Allies' Manhattan Project had produced two types of atomic bombs, and the 509th Composite Group of the United States Army Air Forces (USAAF) was equipped with the specialized Silverplate version of the Boeing B-29 Superfortress that could deliver them from Tinian in the Mariana Islands. Orders for atomic bombs to be used on four Japanese cities were issued on July 25. On August 6, the U.S. dropped a uranium gun-type (Little Boy) bomb on Hiroshima, and American President Harry S. Truman called for Japan's surrender, warning it to "expect a rain of ruin from the air, the like of which has never been seen on this earth." Three days later, on August 9, a plutonium implosion-type (Fat Man) bomb was dropped on Nagasaki. Within the first two to four months of the bombings, the acute effects of the atomic bombings killed 90,000–146,000 people in Hiroshima and 39,000–80,000 in Nagasaki; roughly half of the deaths in each city occurred on the first day. During the following months, large numbers died from the effect of burns, radiation sickness, and other injuries, compounded by illness and malnutrition. In both cities, most of the dead were civilians, although Hiroshima had a sizable military garrison.

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So, if I were to estimate what kind of damage a 10 kiloton bomb strapped to a North Korean ICBM would create it would be likely a minimum of 80,000 to 146,000 people in any city that North Korea hit with a 10 kiloton weapon.

The most likely cities that North Korea might strike would be Seoul, South Korea or Tokyo, Japan or Honolulu like in world war II or if they could get to the U.S. mainland without their ICBM being shot down into the ocean by anti-missile missiles, San Francisco, Los Angeles, San Diego, California or Portland Oregon or Seattle, Washington.

So, if North Korea did this for any reason Pyongyang at a minimum would simply cease to exist. This is likely the biggest deterrent to them doing this in the first place because their government and country would simply be gone along with many millions of people.

But, that doesn't mean this scenario won't happen at some point in the near or far future.

Also, since there doesn't appear to be any "USEFUL" communication between China and North Korea or South Korea and NOrth Korea, or Japan and North Korea or the U.S. and North Korea, there is nothing really to stop this happening much that I can see with the present leader in place in North Korea.