Port au Prince is constructed partly on fluvial deposits (near the airport), and partly on rolling foothills of colluvium and conglomerate.
Structural damage was negligible on the hillside and in the valleys on nodular limestone rising south of the city towards the causal fault. Several embassies are located on these elevated rock regions, and although it is possible that the structural quality of these buildings is superior, many makeshift dwellings were obviously undamaged.
Damage varies from total destruction of city blocks (rare) to large areas of damage with one-house-in-ten, to one-house-in-three, totally destroyed.
Numerous underground utility fractures have occurred as suggested by the flow of water down some streets near the city center. A flow of about 5 liters/minute was observed 23 January from the west side of the destroyed cathedral. The city sewer system is largely unusable.
Many collapsed buildings partially obstructed streets on 23 January. Survivors were seen scavenging materials useful for temporary shelter - corrugated steel and timber.
Garbage trucks were seen 23 Jan moving debris (concrete and steel) from the roads at night. It is not yet clear whether an area has been designated to dump the ruins of the city, the volume of which will be considerable.Enterprising scavengers are breaking up concrete blocks where these have been dumped on the roadside, to sell the concrete and steel fragments as fill.
Electrical cables that were festooned from buildings before the 'quake lay severed or crushed by collapsed buildings and have been draped parallel-to, or across the street, whee rgthey are driven over by cars and trucks. Others dangle from damaged concrete poles. The city is without power.
It is probable that most of Port au Prince was subjected to about of Intensity VII shaking, amplified in the flat and undulating areas of low ground to intensity VIII.
There are no surprises here - damage to buildings is identical to collapsed structures described in a dozen recent earthquakes. The failures are typically caused by ignorance in assembly - thin, unwrapped, or insufficient stirrups in columns, and brittle reinforcing steel terminating at joints without going through them. The aggregate in the concrete was usually local limestone fragments and in a few cases it was clear that the cement mix was weak - the concrete crumbled to scraping with a penknife.
The tank farms near the port survived the shaking as did several water towers, indicating that engineered foundations and structures, properly assembled, survived. Part of the port still functions but two cranes are out of action (see liquefaction report)
The passenger airport buildings were lightly damaged and could still function except they are without public-service power. Water pipes have broken and celing tiles collapsed resulting on cosmetic damage. Numerous X fractures are present on the ground floor between window openings, with some smashed glass doors. The FAA has set up a temporary control tower on the runway.
The photo right is the green swath from the center of the above view of NW Port au Prince. Click on the small photo for a 20 Mb image.
Updated report 27 January 2010.
Most of the structural damage has occurred in poorly assembled concrete frame structures. Well constructed buildings survived largely undamaged. For example, the hospital adjacent the damaged cathedral suffered no damage whatsover.
The number buried as of 24 Jan is 150,000. Many bodies have yet to be removed from pancaked structures.
