  We show that the higher order curvature corrections to general relativity in
the strong gravity regime of near horizon scales produce a rapidly oscillating
and infalling Ricci scalar fireball just outside the horizon. This can generate
the ringdown modes of gravitational waves having the same natural frequency as
those which are generated by the black hole mergers. Our analysis provides a
viable explanation to the echoes in the ringdown modes recently detected from
the LIGO data, without invoking the existence of any exotic structures at the
horizon.
