Multi Black Holes and Earthquakes on Riemann surfaces with boundaries

29 pages, several figures. v2: corrections, more detailed arguments, etc. Update to v3 was an error while trying to update another preprint, v3 is not the right file. v4 reverts to v2. v5: streamlined introduction, various improvments in the expositionWe prove an "Earthquake Theorem" for hyperbolic metrics with geodesic boundary on a compact surfaces $S$ with boundary: given two hyperbolic metrics with geodesic boundary on a surface with $k$ boundary components, there are $2^k$ right earthquakes transforming the first in the second. An alternative formulation arises by introducing the enhanced Teichmueller space of S: We prove that any two points of the latter are related by a unique right earthquake. The proof rests on the geometry of ''multi-black holes'', which are 3-dimensional anti-de Sitter manifolds, topologically the product of a surface with boundary by an interval