From Don Miller
From past experience with this magnitude of earthquake I would suspect many ridge tops in Haiti will have been affected by topographic enhancement of the seismic energy (The ridges act like concentrating lenses). The attached photo shows how the increased shaking cracks open and spreads the ridges. Heavy rain can then have a much more destructive impact, with increased infiltration, as happened only a month later in this example in Vanuatu (M7.1 at about 5 km depth).
I noted that the terraced gardens lower on the 35 degree slopes, which were all reinforced with perimeter tree planting, were virtually undamaged, even after the extreme rainfall experienced later. Vetiver would offer the same degree of resilience to seismic damage on sloping ground I am sure.