Written by Stefan Hansen   

Based on data from U.S. Geological Survey (USGS) a magnitude 7.6 earthquake will hit New York, with a 90-100 per cent probability. When exactly the earthquake will strike isn't known with certainty, but it could happen in the next few weeks.

Using USGS's Earthquake Probability Mapping, it has been calculated that a magnitude 7.6 (or higher) earthquake is to hit New York once every 4 million years. That is indeed a rare event. However, modern instrumental recordings began just 130 years ago (according to USGS), so although a once-in-4-million-year-event is a rare event, we currently have no way of knowing if the 7.6 magnitude earthquake will hit New York City in 4 days, or in 4 million years, for now. As earthquake expert Ronald Hamburger, senior principal at Simpson Gumpertz & Heger, puts it: "the [once in] 10,000 year earthquake is as likely to occur today or tomorrow, as it is 1,000 years from now." The same is true for the once-in-4-million-year-earthquake that - according to the map shown at http://bit.ly/fCZRRt - is expected to hit New York City.

Ronald Hamburger further explains how stress is relieved in the tectonic plates after a large-magnitude earthquake, which makes it less likely for a large-magnitude earthquake to happen in the same location again. So, if we know when the last magnitude 7.6 hit New York, we could count forward 3-4 million years, until the point in time when an earthquake of the same magnitude is most likely to occur again. But we don't have data more than 130 years back, so not expecting such an earthquake in the next couple of weeks is unfortunately based on nothing but a misunderstanding of probability.

If someone proposed to build a nuclear power plant somewhere and said the plant would be able to withstand a once-in-100-year-earthquake, people would object. But if people where told the plant would be able to withstand a once-in-10,000-year-earthquake, they would be much easier to convince. However, in reality - although one sounds better than the other - both power plants could be compromised by a large-magnitude earthquake on the first day of operation. So, what sounds better in a black-on-write safety report, doesn't help us in our colorful everyday life.

In conclusion, people in New York City have good reasons to prepare for a magnitude 7.6 earthquake, and - maybe more importantly - demand city planning that is robust, even to highly unpredictable, but highly consequential, events. Such events are sometimes referred to as Black Swans (a term coined by Nassim Taleb), and even if it seems counter-intuitive to prepare for such rare events, it makes perfect sense, when the veil of ignorance about probabilities is removed from ones eyes.

When it comes to earthquakes, there might be only one way to prevent severe consequences in New York City (and elsewhere), and that is to build cities able to withstand an earthquake similar in strength to the one near Temuco, Chile, on 22 May 1960. This was the strongest earthquake ever registered, at magnitude 9.5, leaving 2 million people homeless. Building cities to withstand a magnitude 9.5 earthquake is a smart solution - not because magnitude 9.5 is the highest ever registered, but because magnitude 9.5 is believed to be the theoretical maximum, as stated by Natural Resources Canada: "Since the tectonic plates have finite dimensions, the magnitude must therefore also reach a maximum. It is believed that the greatest earthquakes can reach magnitude 9.5, which corresponds to the magnitude of the Chilean earthquake." Only by building to withstand the theoretical maximum can we prevent a catastrophe, like the one currently killing the people of Japan, from happening in New York City - tomorrow or whenever it might hit.