13 January 2010

The Haiti earthquake – likely shaking damage to structures

Posted by Dave Petley

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:

Click on the table for a better view in a new window.

This is then helpful for examining the likely level of damage in Haiti, which can be estimated from the USGS shake map:

This should then be compared with the USGS data on the exposed population (MMI=7 and above only):

The USGS suggest that 137,000 people live in the MMI=X zone and a further 710 in the MMI=IX zone. Note that almost all of the news at the moment is from Port-au-Prince, which is in the MMI=VIII zone.

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.