On 13 January 2010, I wake up to emails and radio news about a magnitude 7.0 earthquake in Haiti, and a missed phone message left just before midnight inviting me to be interviewed on the couch for breakfast TV. Too late for that now, but I go straight to the United States Geological Survey earthquake hazards program website to find out what has happened.
The motion was sideways slip on one of the major faults where the Caribbean plate grinds eastwards against the North American plate. A magnitude 7 quake is not necessarily a disaster; there are about twenty of these somewhere in the world in an average year, but I see that in this case the initial rupture occurred at a shallow depth of about 10 kilometres.
This would make the ground shaking much more severe than if the quake had been deeper, moreover the epicentre lay close to Haiti’s sprawling capital city of Port au Prince.
An earthquake is the last thing the desperately poor nation of Haiti needs, coming so soon after hurricanes and flooding in 2004 and 2008. Hundreds feared dead, runs the preliminary report, but as the day wears on estimates of the death toll rise into thousands and then several tens of thousands.
Pictures on news websites show concrete-framed buildings in a state of collapse, with their masonry infill fallen onto the streets below. It is well known how to make comparable buildings earthquake resistant, but it seems that the authorities in Haiti are in no position to enforce building regulations, or maybe they are simply ignorant of the risk. This was the biggest quake in Haiti for at least a century, but any geologist could have pointed out that a significant quake was inevitable at some time.
I wonder about the state of earthquake awareness among the local population, and also among foreign visitors to Haiti, as I listen to their accounts of running in panic from buildings as bricks cascade into the streets. What you should do if you are inside when an earthquake strikes, as school children in Japan, California and China are aware, is to dive under a table and stay there until the shaking has finished. The table will offer you some protection if the roof collapses, but if you panic and run outside you are likely to be hit by falling masonry or glass.
The priority right now, of course, is for material aid, rather than education (donations can be made via DEC.org.uk) - but awareness of earthquake hazards and ways to reduce the risks should become part of the longer term strategy. The next big one could be next week, next year, or not for a hundred years. It could strike Haiti, or Jamaica or southern Cuba.
The maps here show how the pattern of seismicity, as reported by the USGS, developed in the first two days after the initial quake. The squares are proportional to the magnitude of each quake (on the Richter scale), and the colour distinguishes quakes in the last hour, last day and last week prior to the time when the map was compiled. The biggest square is of course the main magnitude 7.0 earthquake, but you can see a whole series of aftershocks (some as large as magnitude 5) happening nearby.
The Presidential Palace in Haiti's capital, Port-Au-Prince, after the earthquake
UK Fire Service Urban Search and Rescue specialists wait to board a DFID-chartered flight to Haiti
Survivors gather in the street
A collapsed building
Damage at Port-Au-Prince docks
Aerial view of survivors gathering in a sports stadium the morning after the quake hit