Effect of black hole mergers on life Would the gravitational energy released in the explosion affect life in any way if it were on a planet close by?
 A: You would not want to be very close to a black hole merger. Suppose you have two black holes of the same mass $M$ and $m = GM/c^2$. The radius of each black hole is then $r = 2m$, and the horizon area is $A = 4\pi r^2$ $ = 16\pi m^2$. Two constraints are imposed. The first is that the type-D solutions have timelike Killing vectors, which are isometries that conserve mass-energy, and with the merger the gravitational radiation is in an asymptotically flat region where we can again localize mass-energy. So the initial mass $2M$ is the total energy. The entropy of the two black holes is a measure of the information they contain and that too is constant. So the horizon area of the resulting black hole is the sum of the two horizon areas, $A_f = 2A$ $ = 32\pi m^2$, that has $\sqrt{2}M$ the mass of the two initial black holes. Now with mass-energy conservation
$$
E_t = 2M = \sqrt{2}M + E_{g-wave}
$$
and the mass-energy of the gravitational radiation is $.59M$. That is a lot of mass-energy!
Does this mass-energy in the gravity wave demolish planets? The Einstein field equation is $G_{ab} = (16\pi G/c^4)T_{ab}$, where I am going to as a back of envelope calculation consider the gravitational wave's matter interaction as just its energy density. The $T_{ab}$ then pertains to the interaction of the gravitational wave with a set of masses, and the mass-energy of the gravitational radiation is absorbed by these masses. Let us focus in on the $T^{00} = \rho$ or the mass-energy density. To get this density was consider this mass-energy in the form of a gravity wave in a volume $V = (4\pi/3)r^3$. The $G_{00}$ curvature term is then
$$
G_{00} = \frac{16\pi G}{c^4}Mc^2/V = 4.1\times 10^{-43}N^{-1}\times .59M\times 9.0\times 10^{16}m^2/s^2/V,
$$
where I am now going to assume $M = 10M_{sol}$ $ = 2\times 10^{30}kg$
$$
G_{00} = 4.4\times 10^{6}m/V
$$
Now assume you are $1\times 10^{9}$m away. The curvature is then about $1\times 10^{-21}m^{-2}$.
How much gravity would I expect form this? The Riemann curvature for gravitation at the surface of the Earth is $R = GM/c^2r^3$ or 
$$
R = \frac{6.7\times 10^{-11}Nm^2/kg^2\times 6\times 10^{24}kg}{9\times 10^{16}m^2/s^2\times (6.4\times 10^{6}m)^3} = 1.7\times 10^{-23}m^{-2}.
$$
Thus if you were about a million kilometers from the coalescence of two black holes the curvature induced would be comparable to the gravitational curvature here on Earth.
This sounds a bit surprising, for if $.59M$ amount of mass energy is generated by the collision of two black holes, then that would seem to imply a huge amount of local violence. It is that coupling term $\frac{16\pi G}{c^4}$ being so small that makes the gravitational effect so small. It is why detecting gravitational radiation from many light years away is so difficult.
A: Your question differs from the title, in that an "exploding" black hole happens when the the mass is very tiny and thus the Hawking effect causes an almost instantaneous release of all the remaining mass as energy.  This would not have much effect on anything, although if it happened right inside your body the total ionizing radiation would be enough to cause cancer with a fairly high probability.
So assume we are talking about black hole mergers, as in the title of the question.
Let's make some further assumptions:" 


*

*The life in question is on a planet which before and after the merger was not inside the event horizon or either black hole.

*The planet in question was orbiting an active star rather than one of the  black holes (although the star/planet system could have been orbiting a black hole).  Without such a star, the life would not be able to exist.

*The planet is made of ordinary planet material (rocks, iron core, or whatever) and was not long ago pulled apart by tidal forces associated with being near to a black hole.  (The gravity gradient near the event horizon of a massive black hole overcomes any molecular adhesion forces. and would shatter the planet.)

*The black holes are of the size of a few to a few hundred stellar masses, rather than having the mass comparable to that of a galaxy.   
So when the two black holes merge, there is a considerable gravitational wave pulse, which (depending on the net angular momentum) is dominated by quadrapole radiation (meaning it falls off as r^4) but the angular momentum can contribute dipole radiation terms and gravity waves.  
When we consider the effect on the life itself, these gravity waves would not be strong enough to disrupt the molecular forces locally, so they would not immediately kill off the life.
When we consider the effect on the life itself, these gravity waves would not be strong enough (even integrated over the planetary mass) to disrupt the structure of the planet.
So on first thought, the life survives.
But the star is a MUCH larger "test mass" and will be  affected by the waves, enough to change the distribution of densities enough to casue a temporary (thousands of years) profound change in its energy output.  This might well slowly destroy the life on the planet, by cold or excessive heat.
