Why Earthquakes have Doubled this Year

If you think there have been more earthquakes than usual this year, you may be right. A new study recently found there were more than twice as many big earthquakes, worldwide in the first quarter of 2014 as compared with the average since 1979. So should we be worried?

After living in Turkey for a few years there are certain things you do almost without thinking about it: You never drink the tap water, you always, always check your restaurant bill and you notice every once in a while, the odd shake of the ground or just occasionally feel a jolt that can make you uneasy on your feet. These are of course earth tremors from deep underground or they are the reduced energy of a more distant bigger earthquake. On the whole people don’t tend to dwell on them too much and just accept that earthquakes will always be an issue in this region, and so you get on with your lives hoping that the next ‘Big One’ will be far, far away from you and yours. However, this head in the sand approach has been a little harder to achieve these past months after several TV news items about earthquakes, one after the other, have filled our TV screens.

Photo by Leonardo Hendler

Tom Parsons, a research geophysicist with the U.S. Geological Survey (USGS) in Menlo Park, California, and co-author of the study with Eric Geist, told us last week that we have recently experienced a period that has had one of the highest rates of great earthquakes ever recorded.
But even though the global earthquake rate appears to be on the rise, he said the number of quakes can still be explained by random chance. With so many earthquakes rattling the planet in 2014, Parsons actually hoped his study might find the opposite — that the increase in big earthquakes comes from one large quake setting off another huge shaker. Earlier research had shown that seismic waves from one earthquake can travel around the world and trigger tiny temblors or aftershocks elsewhere and must admit that this was also my own pretty set view until now.

When I first moved to Turkey, many years ago, I was very aware that it was a higher than normal earthquake risk area. The reason for my awareness was because the fringes of Istanbul, the city I initially moved to, where rattled by two large earthquakes within weeks of each other in 1999. The first quake that hit with a magnitude 7.4 on the 17th August was centred close to the nearby city of Izmit. It caused extensive damage, and it was estimated that up to 17,000 people were killed, with a further half a million made homeless. The second quake struck less than 3 months later with a magnitude 7.2 shake near the city of Duzce, which lies about 100km further east from Izmit. This time the death toll was less than a thousand but the affect of two large earthquakes, so close together understandably made people believe that one must have set of the other. And so it created a climate of fear for quite a while after the events. Indeed, I often saw people testing walls with their hands, or perhaps after a heavy lorry drove by rattling windows, some people would actually run out into the open, if only to confirm that the shake had nothing to do with the Great Anatolian fault, which cuts right through Istanbul.

Photo by Yelingyang

In the days that followed the Duzce quake I remember many world seismology experts coming and going and making various predictions. The one I remember most of all was an assessment that Istanbul itself would suffer a similar if not more devastating earthquake within the next 25 years. That expert, whose name I have long forgotten dramatically told us that because of the unpredictability of earthquakes, it could be in 25 years time or it could happen the day after tomorrow. That was in 1999, so by his estimation, the next big quake must hit Istanbul sometime in the next 10 years. The other thing that sticks in my mind from all of those news items back then was learning just how difficult it was to make any prediction at all, other than those based on historical records of earthquakes past. While some still declared that the Duzce earthquake must have been triggered by the Izmit earthquake, that seemed to be based on nothing but supposition.

Anyway, fifteen years on few people seem to be as bothered as much as they were in 1999 and a certain fatalism has taken over. If it happens it happens – what can I do?’ or from the more religious minded ‘If it kills me, then of course it is simply Allah’s will.’ Although that later statement has been used for as long as I can remember as an excuse for many different things and is often put forward as a big factor in the way many people drive so badly here, with little care and attention to the road to the point that the death rate on the roads is so many times higher than in most other countries.

As I said earlier I had gradually leaned towards the belief that some earthquakes do set each other off, but according to the study I seem to be wrong. Despite the recent earthquake storm, they concluded that the world’s great earthquakes still strike at random. The average rate of big earthquakes — those larger than magnitude 7 — has been 10 per year since 1979, the study reports. That rate rose to 12.5 per year starting in 1992, and then jumped to 16.7 per year starting in 2010 — a 65 percent increase compared to the rate since 1979. This increase accelerated in the first three months of 2014 to more than double the average since 1979, the researchers report.

“The rise in earthquakes is statistically similar to the results of flipping a coin,” Parsons finally declared, “sometimes heads or tails will repeat several times in a row, even though the process is random. Basically, we can’t prove that what we saw during the first part of 2014, or since 2010, isn’t simply a similar thing to getting six tails in a row.”