Since Gravity is the force that defines the limits of a black hole, gravity does not escape a black hole; it is the cause of the black hole. Since a black hole is a "Quantum Singularity" in which the "Quantum Force" is Gravity, Gravity in and of itself is not affected by the gravitational force produced by the Singularity. Very small particles and energy radiation associated with those particles that are not affected by gravity (neutrinos etc.) pass through the event horizon with ease. Light wave particles (photons) and larger particles (electrons etc.) that are affected by gravity’s pull cannot penetrate the event horizon. At this point no one has ever measured the speed of gravity. There is no evidence to say that the speed at which gravity particles (waves) spread has to match that of the photon. There are some who calculate the speed of Gravity may be up to 4 times that of the speed of light.

: Here is something I found very interresting and exactly : what was concerning me about gravity... read on... :)

: http://www.ldolphin.org/vanFlandern/gravityspeed.html

: "When the subject of "black holes" first comes up in physics : classes, a frequently asked question is "If nothing can escape the event horizon because nothing can propagate faster than light, how : does gravity get out of a black hole?" The answer usually provided is that the field around a black hole was frozen into the : surrounding space-time prior to the collapse of the parent star behind an event horizon, and has remained in that state ever since. By : implication, there is no need for continual regeneration of the external field by causal agents from the source.

: However, let us suppose we have a binary black hole, with the two collapsed stars in elliptical orbits around one another. Then each : field must be continually updated by a changing contribution from the orbiting field of the other. How does each field know what it is : supposed to do if it is no longer communication with its source mass hidden behind an event horizon? If the curvature of space-time : at a point near black hole A becomes zero because black hole B is equally distant, what makes it non-zero again once black hole B : recedes?"