I’m not sure how long I’ve been writing a weekly digest for Decoded Science, but it’s a matter of years rather than months — long enough to learn, as any regular readers will have seen for themselves, that after a while earthquake patterns repeat themselves.
That means the earthquake digest must, too. And while every event is unique and most of them are interesting (to me, at least) there’s no escaping the fact that I’ve found myself typing the same thing, over and over again. If anything says it’s time for a revamp, then that’s it.
From here on, then, the weekly earthquake digest is reborn as a more wide-ranging, and much more loosely-defined, round-up of what’s been going on in the Earth system over the past week (or sometimes, if the news is interesting, a bit longer). Some weeks there might be no earthquakes, other weeks, nothing but. We’ll see how it goes, and hope you find it fresh and interesting.
The Year Just Passed: 2017 in Earthquakes
The United States Geological Survey’s real time earthquake archive is a truly wonderful thing. Not only does it allow you to search for earthquakes but it allows you to download them into a spreadsheet and play with them. And I can’t resist a spreadsheet.
Unfortunately I don’t have the computer power to download all the recorded earthquakes on the database over the last year, or the time to manipulate the data, so that my summary of the year’s seismic activity is necessarily limited. But I hope, nevertheless, that it’s interesting.
So how many were there? Looking only at those of at least magnitude 4 (which is about as much as my computer can handle) gives a total of 12,960 earthquakes. The largest of these was M8 off Mexico in September, and there were a further seven of between M7.0 and M7.9.
As a rule of thumb, the number of earthquakes of each magnitude increases by a factor of ten, so that for every tremor of at least M7 we might expect ten of M6. Interestingly, when we look at the total figures, this broadly holds true for the intermediate magnitudes in 2017 on the basis of the available data (which may be incomplete). There was one earthquake in the category of M8+, seven of M7+, 104 of M6+, 1,453 of M5+ and 11395 of M4+.
The geographical pattern of these earthquakes also gives a more complete picture over a year than over a week. The map clearly shows the relationship between major plate boundaries and significant earthquake activities.
More Earthquakes to Come?
Earthquakes are dangerous, though the key factor isn’t the magnitude but the vulnerability of the population. Mercifully, 2017 didn’t produce anything remotely as disastrous as previous years have done. But what about 2018?
Earthquake prediction is the seismologists’ Holy Grail: being able to say when and where an earthquake will strike and how big it will be would certainly save tens of thousands, if not hundreds of thousands, of lives. We’re a long way from that, though we do know the areas where major earthquakes are likely to occur.
At the moment we deal in probability rather than more detailed prediction. One very worrying development that caught my eye this week is that seismologists in Japan have increased their forecasts of the probability of a major — i.e. at least M9.0 — earthquake off Japan and, more specifically, off the eastern coast of the island of Hokkaido.
The possibility is considered ‘very high’ which, in layman’s terms, is a 40% chance within 30 years. So it’s unlikely, perhaps, in 2018 — but certainly something not watch for.
A Flutter on Social Media
Twitter is my favourite social medium. I use it as an information source, keeping facts flying across my computer screen and keeping me updated. Much of it is either duplicate or irrelevant; some of it is fascinating; and, just occasionally, you come across something that’s fun.
If you follow the trivialities of Twitter, you may have seen a bit of a trend for the knock-out cups, where people vote for their favourite biscuit/Christmas song/breed of dog or whatever. I don’t have much time for these, but it’s recently extended into an area where Earth science geeks can get just as involved.
It began with the mineral cup (search Twitter for #mineralcup) where mineralogist got all angsty about the relative merit of their favourites and where olivine defeated zircon in the final. Then it went on to the dinosaur cup (#dinocup), which didn’t catch my attention in quite the same way. (For information, triceratops came out champion.)
I did get very engaged with the most recent, the fault cup (#faultcup) in which major crustal fractures in the Earth’s surface — those very ones which are represented on the map by earthquakes — fought it out (or rather, their adherents fought it out on their behalf).
As is so often the case, the big beasts ended up fighting it out and, if I was disappointed that Scotland’s own Moine Thrust didn’t make it past the semi-final stage, the East African Rift was a worthy eventual winner.
Okay, so this last item is a bit flippant, but it’s an illustration of how science education and information is changing. If you’d followed any of those threads, with contributions from expert and and interested laymen alike, you’ll have learned a lot about seismology, palaeontology or mineralogy without even realising it.
Learning about science can be fun.