why did the tsunami affect the west side of Sri Lanka and India?

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Clarification of Question by payamp-ga on 17 Jan 2006 20:12 PST

Thank you for the answers however what explains certain parts of the
Sri Lankan west coast being devastated while nearby shoreline was
untouched? Any ideas.

Check out this animation: http://staff.aist.go.jp/kenji.satake/animation.gif

Indeed. The animation illustrates that the culprit is basic wave
diffraction. The wave front tends to follow the contour of the
obstacles, which in this case are Sri-Lanka & India. The longer the
length of the waves, the better they can wrap around the far side of
the obstacle. In the case of the tsunami, the wavelength was enormous.