Earthquake prediction: if only

Posted on April 7, 2009 by Chris Rowan

Because both Ole and Kim have already provided astute and insightful commentary, there’s no real need for me to spend much time on the media storm surrounding Giampaolo Giuliani, who has been loudly claiming vindication after his warnings about an imminent earthquake in the region were shut down by the Italian authorities at the end of March. Suffice to say, one successful “prediction” (if you count within a week and 30 km as successful) does not a robust warning system make: making the leap from elevated radon levels – or any of the other proposed precursors, like low frequency EM radiation – to a useful prediction is fraught with as-yet-unsolved problems. Chief among these are distinguishing false positives (you get the precursor, but no big earthquake) and understanding what, exactly, these signals are telling us about the stress state of the crust, so we can pin down potential magnitudes and timescales beyond “somewhere around here, maybe sometime soon.”
Any geologist would be celebrating a genuine, proven, method of earthquake prediction: but we’re clearly not there yet. Right now, the best we can get is a hazy view of tectonic storm clouds building on the horizon, and we lack even the equivalent of a barometer, let alone advanced tools like weather satellites, to give us a more specific forecast. It would be irresponsible to claim otherwise.

Categories: earthquakes, geohazards, geology

Tectonics of the L’Aquila Earthquake

Posted on April 6, 2009 by Chris Rowan

Early this morning a magnitude 6.3 earthquake struck Italy, centred on the city of L’Aquila to the north-east of Rome. The BBC reports that at least 150 people have been killed, and tens of thousands may have been made homeless.
Earthquakes in this region are not unusual: this map of seismicity between 1981 and 2002 from the INGV shows, Italy experiences frequent shallow earthquakes, mainly distributed along the Apennine mountain range that runs along the northeast coast (sorry for the squint-inducing nature of this – you could also have a look at this rather crowded USGS version). Typically these earthquakes are smaller, a high magnitude 5 at most, but nine of magnitude 6 or greater have occurred in the last hundred years or so.

recent Italian seismicity

All this activity is the result of Italy being right in the thick of the slow collision between the African and Eurasian plates that has, amongst other things, resulted in the uplift of the Alps. At first glance, it is therefore quite surprising to see that the focal mechanism for this earthquake is characteristic of an extensional earthquake, due to stretching of the earth’s crust, not a compressional one. The extension is oriented in a northeast-southwest direction, at right angles to the Apennine range:

focal.png

So why is extension occurring in a mountain range? The tectonic history of the western Mediterranean is actually quite complicated; rather than being the last remnants of a large ocean that has been mostly destroyed by subduction as Africa and Europe move together, the oceanic crust here has actually all been created by back-arc spreading in the last 40 million years or so, as the collision zone (marked by the red line which runs around the east and south-east coast of Italy and Sicily and into North Africa), has migrated south and east away from Europe, stretching out the crust in the over-riding plate as it does so.

simple tectonic map of the W Med

So although at a broad regional scale two plates are colliding, at a more local level the current back-arc spreading in the Tyrrhenian Sea to the southwest appears to be a major driver of tectonics in Italy, to the extent that thrust faults that built up the Apennines are now being reactivated as extensional normal faults. Unfortunately, this switch doesn’t make the earthquakes themselves any less damaging when they do occur.

Categories: earthquakes, geohazards, geology, tectonics

New Precambrian macrofossil discovered

Posted on April 1, 2009 by Chris Rowan

[Update: It should come as no surprise that W. Haldanei comes not from southern China but some rather extreme photoshopping of a picture of a cute (and very much alive) bunny rabbit. The ‘biomarkers’ are all found in chocolate. And Rolf Harris is not a paleontologist (though I’m sure he could draw a mean dinosaur).]
China has been the location of many of the more spectacular fossil discoveries of recent years – from feathered dinosaurs to claimed Precambrian embryos – but the latest may well be the most spectacular, and paradigm shattering, yet.

Do you know what it is yet?

When fossil hunter Rolf Harris came across a weird looking smudge in 650 million-year old shales in the Heifuldya region of southern China, he was convinced that he had discovered something very important. One high resolution laser scan later, and this intuition is confirmed: this is by far the most complex Precambrian fossil ever discovered. Unlike other Ediacaran species, which generally appear to be nothing more than multicellular airbags, this specimen appears to be possess something like a head (on the right), with curious floppy projections on either side; the slightly lighter pit could even be some form of primitive eye. A bulky body is somewhat lacking in internal details, but there are some suggestions of numerous small keratinous projections of unknown function, and stumpy limbs of some sort project from the left side.
Organic biomarker evidence from the shales is also extremely interesting, and suggestive of complex biochemistry at work in the environment that this critter moved about in: phenylethylamine, theobromine, and alpha-D-glucopyranosyl-(1-2)-beta-D-fructofuranoside have all been identified, and are, Harris says, just like the fossil itself, a little “out of their time”. “We find these things all over the place in the modern world,” he said, “but finding them in abundance so long ago – well, it’s really shaken things up from an evolutionary perspective.”
Harris has named the new species Wassahpdug Haldanei, with the specific name coined in honour of the man who rather prophetically discussed the evolutionary significance of a find such as this, way back in 1950s.

Categories: bloggery

Death to the outline slide

Posted on March 26, 2009 by Chris Rowan

Has anyone else come to the conclusion that opening your talk with this slide is utterly worthless?

slide1.png

What, you’re describing your results after your methods? That’s so… like every other conference presentation I’ve ever been to.
What makes this even more annoying is that your opening slide could be put to a far better use. I’ve lost count of the number of talks I’ve been to where the speaker dives straight into the nitty gritty technicalities of their study – and therefore loses virtually everyone who doesn’t occupy their particular sub-sub-field within the first three minutes. Rather than wasting a minute describing the order you’re going to present things in the following 15, you could spend it explaining why people should stay awake to hear what you have to say.
For example:

slide2.png

Or:

slide3.png

Or even:

slide4.png

I fully admit that it’s taken me a while to come to this conclusion – which is why I’ve been encouraged by what I’ve seen in the last couple of days here in Edinburgh. The School of Geosciences were having their annual post-graduate conference, and virtually every presenting student had dumped their outline slide in favour of telling their audience why they should care about their research. It was really heartening to see – and it made the sessions far more engaging. Hopefully it’s a habit that will stick – and spread upwards.

Categories: academic life

It’s official: we really have saved the ozone layer

Posted on March 23, 2009 by Chris Rowan

ResearchBlogging.org During our little climatic digression in this week’s podclast, Chris brought up a study that I hadn’t heard about, in which Paul Newman (no, not that one) of NASA’s Goddard Centre (who have a nice write-up) and his colleagues play a game of climatic what if: what if the discovery that chlorofluorocarbons (CFCs) destroyed stratospheric ozone had been ignored, and were not phased out in the decade following the signing of the Montreal Protocol in 1987? Do our more sophisticated climate models, which can more accurately simulate atmospheric chemistry and wind patterns, confirm the hypothesis that if we had continued to emit CFCs and other ozone destroying chemicals, the ozone layer would have been severely damaged?
To answer this question, Newman et al. ran two scenarios in the same climate model, and charted the evolution of stratospheric ozone in each. The first model was based on the current (low) emissions of ozone-destroying chemicals resulting from the implementation of the Montreal Protocol; in the second, rather poetically named “world avoided” model, CFC emissions increase by 3% a year (“business as usual”) after 1974, when the ozone alarm was first sounded (and was presumably ignored in this parallel universe).
Animations fully depicting the results of both scenarios between 1974 and 2065, are available, and are well worth a watch. Below I show some edited highlights: side-by-side comparisons of the two models during September/October (southern hemisphere spring, when the Antarctic ozone hole reaches it’s maximum extent) in 2008, 2020, 2040 and 2060.

2008.png
ozone_scale.png

Continue reading →

Categories: climate science, environment, paper reviews