  Recent numerical relativity simulations of mergers of binary black holes
suggest that the maximum final value of $a/M$ is $\sim 0.95$ for the
coalescence of two equal mass black holes with aligned spins of the same
magnitude $a/M=0.994$ which is close to the upper limit $a/M=0.998$ of
accretion spin-up shown by Thorne. Using the WKB method, we suggest that if
quasinormal modes with $a/M \sim 0.95$ are detected by the second generation
gravitational wave detectors, we could confirm the strong gravity space-time
based on Einstein's general relativity up to $1.33M$ which is only $\sim 1.014$
times the event horizon radius and within the ergoregion. One more message
about black hole geometry is expected here. If the quasinormal mode is
different from that of general relativity, we need to find the true theory of
gravity which deviates from general relativity only near the black hole
horizon.
