13 January 2010
Over the last few years a number of studies have examined the level of damage associated with the intensity of shaking in earthquakes. The table below shows the relationship between shaking intensity (MMI) across the top and different types of building down the side. The number is the percentage of buildings damaged or collapsed:
This should then be compared with the USGS data on the exposed population (MMI=7 and above only):
This GoogleEarth image shows some of the urban slums on the edge of Carrefour, in the MMI=IX zone, before the earthquake. As most of the buildings here are likely to be unreinforced masonry, the building collapse rate is probably 80% or more. This could be higher due to the effects of the slopes, which both increase the intensity of shaking and make the foundations less secure.