if it was a real bomb-I am not convinced-than it works just like the claymore antipersonnel mines.
Claymore mine is about a 3/4 kilogram Semtex plus the iron shrapnel, total wight is about 2 kilograms.
Now from the news, the first report was 2 kg Semtex was used, and it was shrapnelled, but we do not know if 2kg is the Semtex only, or the explosive plus iron shrapnel combined weight.
But if we assume the 2kg was the bomb zusammen, then we can have the claymore blast radius as a starting point.
The following picture shows how it works:
But let us not forget, the blast of claymore is directed, because it is used as perimeter defence, or as ambush: you are standing behind and have to avoid the good news zapping towards you. But no need to play about if you are suicide bomber*, you want everybody around blasted, and you do not have to worry about yourself. So, your suicide bomb is not directed as the claymores are. So the blast is not in a small degree arch, but a 3D 360 degrees blast. The later news of 5kg bomb (I even heard 7kg today), does not mean necessary it is more lethal than the directed claymore would be. Why? Because of the 360 degree. That means shrapnel zapping into the ceiling, into the floor, into yourself, too-and the remaining into the people around you. So we can say 30 meters around the bomber is the first, lethal killing zone.
What is happening to the people in the killing zone? Shrapnel cut you to peaces-not just falling down like the people of the blast video. Yes legs and arms flying-none of it seen on the aftermath video-and, if you are not close enough for the blast heat to cauterize your veins, you will bleed like a sucking piglet-and no blood seen on the aftermath video.
And there is no screaming on the aftermath video: maybe all victims were in shock, but those who were not should scream their heads off from the pain. So I am not at all convinced what we see is reality.
*About the suicide bomber (warning: I will speculate here a bit, too, and his head will be on the picture)
First it was a supposed chechen widow ( I am happy it was not, imagine the poor woman arriving to Allah's paradise, all excited, and she gets her 72 virgins! Now 72 virgin boys gangbanging you, even if you are a muslim woman, is not as much fun I think as she may imagine...)
Now they say it was him, I am sure the Russian CSI uses all black-and-white photomachines, yeah.
They say not chechen, but maybe Arabic (my speculation he will be "Iranian Al-Quaeda" or "iranian intelligence"), and this have to turn out within the week if we consider the 9/11 timeline.
The interesting will be if they will claim he was muslim.
Because his last shout was "I will kill you all!"
If you are a muslim, and you are before your death, in order to meet Allah and your sins to be forgiven (suicide bombing is sin all right), you have to recite the Shahada! "La illah il Allah, la Muhammad ras ullah", meaning "there is no God but God, and Mohamed is His Prophet".
So if any suicide-bomber muslim's last words are "Allah Akbar!" (like Atta on the plane before zapping into WTC), or "I will kill you all!", or even "Luke, I am your father!", do not buy it. Just the Shahada.