I’ve heard many guestimates of the size of the recent explosion in the Chinese city of Tianjin. One commentator measured the size of the fireball and claimed it was 21 kilotons - which would make it bigger than the 16kt atomic explosion at Hiroshima. I found that difficult to believe at first because of the destructive force of that bomb and the numbers of casualties - but that was an air burst in a populated city centre with cheap buildings.
Anyway, the question I have is multifold - how does one calculate the size of such an explosion? Can it be done using the size of the fireball or is it much more complex? And just how big was the Tianjin explosion?
The USGS is reporting seismological readings of a magnitude 2 or 3 earthquake. It’s difficult to pin that down because the Chinese seismographs are considered suspect and the explosions occurred on the surface (water? boat? land?). The seismographs used to determine magnitude are outside of China. Another unidentified source was claiming/interpreting the force of the blast was equivalent to 3 to 21 tons of TNT.
Which is almost certainly underestimating the magnitude by a very wide margin. Remember, he said “tons” not “kilotons”, which is 1,000x larger.
For comparison’s sake, the Texas City disaster, which killed 581 people and leveled two square miles of the city, is estimated at nearly 3.2 kilotons equivalent.
The China Earthquake Networks Centre said the magnitude of the first explosion was the equivalent of detonating three tons of TNT, while the second was the equivalent of 21 tonnes of the explosive.
My guess is that your commentator either said 21 tons, not 21 kilotons, and you misheard, or else he misspoke. Seems likelier than being off by a factor of 1,000.
Wiki says the OK City blast was equal to 5,000 pounds of TNT, or 2.5 tons (not kilotons). But it should be noted that most of the fatalities were caused by the building’s collapse, not the explosion itself.
Watching videos online of the explosion, it is formidable to think that the bombs dropped on Japan were about 1000 more powerful assuming the explosion in China was about 15-20 tons.
The upper estimate of the 2013 West, Texas fertilizer explosion was 20,000 lbs of TNT (10 tons). The videos of the 2nd Tianjin explosion reminded me of the West explosion videos. Sounds like Tianjin was about twice as big then.
Has anyone yet identified the explosives involved?
I am curious because my personal experience with explosives is that they require a shock to detonate; ie: they require a detonator, and they do not explode when exposed to fire.
In fact in a previous career, we commonly burned C4 to heat our meals.
So what was the “explosive” in China that was detonated by flame?
I was at home in Las Vegas when this PEPCON disaster - Wikipedia happened. The reports in Wiki seem to be saying about 1.0 kilotons.
From Pepcon to my house was about 18 miles. I was sitting inside eating lunch facing my rear sliding glass door. Which was on the side of my house facing away from the plant. I was astonished to see the glass suddenly flex inwards enough that I was sure it was going to shatter in on me. But it held.
The noise was quite loud, but more of a lengthy boooom than the quick bang of a firecracker, gunshot or nearby artillery. I quickly climbed the roof and was amazed to see the blast cloud growing on the far side of the valley. I’d assumed it was a lot closer from the intensity of the blast. By that point in my career I’d dropped a lot of bombs and witnessed a lot of bombs and artillery from the ground. This was definitely the biggest explosion I’d ever seen or felt.
Again, my experience with nitrates is that they require a detonator to blast. Don’t know about calcium carbide, except if you mix it with water it makes a nice fizz.
There is some speculation that the first explosion was caused by some chemical reaction that released an explosive gas, which I imagine would be more likely triggered by, say, an open flame.
