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What’s with all the earthquakes lately?

What is going on?

A magnitude 8.3 earthquake strikes the south of Samoa on Tuesday, triggering a tsunami. Then, 16 hours later, a magnitude 7.6 quake occurs 30 miles off the east coast of the Indonesian island of Sumatra.

Why has there been a large amount of seismic activity in the Asia-Pacific region over the past few weeks? Clive Collins, Senior Seismologist for GeoScience Australia, gives us some answers:

Samoa and Indonesia are just over 6,000km apart. Are these earthquakes, only 16 hours apart, linked?

The short answer, says Collins is that “we don’t know, we don’t think they are linked directly”. Although there is “some evidence that sometimes large earthquakes can cause distant earthquakes to occur some time later”, Collins says that there is “no proved cause and effect”.

While it is unlikely that the earthquake near Samoa caused the earthquake in Indonesia, “in the big picture they are linked as they are both on same tectonic plate”. In layman’s terms, both earthquakes are ”due to the movement of the Australian plate”.

Over the last few weeks there has been considerable activity around the Australian plate, in Java, Maluku and even the south-eastern suburbs of Melbourne. What’s going on?

The earth’s plates are always moving,” says Collins. “The Australian plate is drifting north whilst the South Pacific plate is moving westwards” and when these plates meet, seismic activity is triggered.

More specifically, in the case of the earthquake in Samoa, “the Pacific plate is being pushed underneath the Australian plate” and this activity causes “breakages and build-up of pressure which causes earthquakes”.

Is it possible that this seismic activity could cause any volcanic activity?

Yes. As the plates meet and crash, says Collins, “debris from the crash heats up and melts”. Then, as it moves down deeper under the plate “it eventually has nowhere to go and gets pushed upwards”. The result: a volcanic eruption.

Are more earthquakes expected?

Lots of aftershocks and small earthquakes are expected, says Collins. However, “we don’t know if there will be another large one in the same place in the near future. [However] areas to the south and the north of the breakages may break and cause more earthquakes.” [After this interview was conducted reports started coming in that another major earthquake had hit Sumatra]

There has been an increase in seismic activity in the Indonesian fault line since the 2004 Asian tsunami. What causes such an upswing in earthquakes?

According to Collins, “this was such a big event and caused a whole lot of the boundary to break which puts pressure and stress on the rocks and surrounding areas”. Yet, while “earthquakes occur in clusters, if you look at a long enough time span, on average, the rate of earthquakes doesn’t change”.

Could this be at all related to the effects of climate change?

Not directly, not these ones, this will happen regardless,” assures Collins. Other earthquakes though “may be related [to climate change]. If, for example, the polar ice caps melt you get more water in oceans or more weight in some places or pressure released in some places” which can cause plates to shift and earthquakes to occur.

Can Will Smith really save us?

Who knows, he can have a try. It’s a bit of an uphill battle.”

View our Crikey Clarifier archive

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  • 1
    Robert Barwick
    Posted Thursday, 1 October 2009 at 2:01 pm | Permalink

    What the?!!!!! I know you’re an intern and all so I’m sorry for this but what an absolutely goddamn moronic thing to ask. “Could this at all be related to the effects of climate change?” Wake up! How brainwashed are you people? Climate change is happening, it’s always happened and it always will happen. Tectonic plate shifts too have always happened and always will happen. It’s nature, and nature can kill. If the climate change propagandists have been so effective that a wanna-be reputable organ like Crikey can query a “link” between an earthquake and climate change, now I do fear for the future. And fyi, if ice caps melt there will be enormous earthquakes, it’s called isostatic rebound, and it too is 100% natural. You should have been around in 16,000 BC and 11,000 BC when there were rapid ice melts and the oceans rose quickly. The climate change alarmists back then made sacrifices to the gods to stop it.

  • 2
    meski
    Posted Thursday, 1 October 2009 at 2:08 pm | Permalink

    ”due to the movement of the Australian plate” - Shhh! Don’t say that, those pesky Indonesians will blame us for it! :^)

  • 3
    jungarrayi
    Posted Thursday, 1 October 2009 at 2:09 pm | Permalink

    Erratum (Moot point): The Sumatran earthquake struck off the west coast of Sumatra not the east coast.

  • 4
    Most Peculiar Mama
    Posted Thursday, 1 October 2009 at 3:18 pm | Permalink

    …Could this be at all related to the effects of climate change?

    “Not directly, not these ones, this will happen regardless,” assures Collins. Other earthquakes though “may be related [to climate change]. If, for example, the polar ice caps melt you get more water in oceans or more weight in some places or pressure released in some places” which can cause plates to shift and earthquakes to occur…”

    24K Comedy GOLD!!

    Using Collins’ rationale, if the entire population stood at either of the poles we could flood the globe.

    Great stuff…thanks for the laugh, Mel.

  • 5
    stephen martin
    Posted Thursday, 1 October 2009 at 3:22 pm | Permalink

    There was a brief mention of another earthquake on the ABC news this morning, but I have heard no follow up, apparently there was a 6.3 quake near La Paz, in Peru.

  • 6
    Mark Duffett
    Posted Thursday, 1 October 2009 at 3:26 pm | Permalink

    I’m pretty sure Clive meant the 2004 quake caused a large section of the plate boundary near Indonesia to break, not brake.

    It needs emphasising that the seismic activity — >volcanic activity connection generally only holds for the broadest scales in both time and space. I wouldn’t be expecting new eruptions in the vicinity of this week’s quakes any time this millennium. Note however that the reverse does actually operate, i.e. volcanic activity is generally accompanied by seismic activity associated with magma and other fluid movement. But these types of seismic events are generally orders of magnitude smaller than the 7s and 8s that hit Sumatra and Samoa.

    It may help to think of earthquake events around a plate as a bunch of lights set to flash on for a second at random intervals, with each flash representing a seismic event. Every so often, you’re going to get two or three lights flashing on simultaneously, even though they’re independent of each other.

    Robert Barwick, I have some sympathy with what you’re saying (it was a silly question, betraying a troubling general ignorance of how our planet works), but it’s not true to say that melting ice caps will result in ‘enormous’ earthquakes. Small earthquakes, yes, in fact there has already been a measurable upswing in seismic activity around the coast of Greenland associated with ice unloading. But these are, again, literally orders of magnitude smaller than the Samoan and Sumatran events. The lithosphere is able to take up the broadly distributed vertical stresses of isostatic loads by bending and flexing, with only minimal brittle failure (i.e. earthquakes). Remember Scandinavia is still rebounding at a fair clip from the last ice age, and there’s not a lot going on there seismically.

  • 7
    stephen martin
    Posted Thursday, 1 October 2009 at 3:33 pm | Permalink

    Clive Collins, Senior Seismologist for GeoScience Australia, gives us some answers. I would think that a senior professional would know more about his profession than a couple of the commentators above. It is a perfectly reasonable hypothesis that redistribution of mass due to melting of ice caps could have an effect on tectonic plates, particularly those that were unstable to begin with. After the last ice age I believe that there was, for example, a great rebound in land mass that had been covered with sheets of ice. Greenland and Antarctica have ice kilometers thick, if it were all to melt the sea level rise would be catastrophic.

  • 8
    Mark Duffett
    Posted Thursday, 1 October 2009 at 3:37 pm | Permalink

    Thanks for that, Stephen Martin, an excellent demonstration of how random independent events get erroneously linked in the public mind. The only true correlation of these events is with the level of media interest. I’ll wager the 6.3 in La Paz would not have gotten a mention if not for the temporal proximity to the Samoan event. This is how notions of ‘an upswing in earthquake activity reinforce themselves.

  • 9
    Mark Duffett
    Posted Thursday, 1 October 2009 at 3:40 pm | Permalink

    Hope you’re not looking at me, Stephen. I do actually have a PhD in geophysics.

  • 10
    Jim Reiher
    Posted Thursday, 1 October 2009 at 3:45 pm | Permalink

    Climate change deniers are a fascinating group. In response to Robert, a few comments:

    As I read the above article, and got to the climate change question, my first thought was: Melanie is asking this because this is a “Crikey Clarifier” and some people “out there” might just be wondering if there is any link between increase in earth quakes and climate change.

    That was my first thought. And of course the correct answer was given: no. They happen for other reasons.

    Not rocket science… but let’s not assume that the writer was assuming a link in asking a question that some people might need clarity on. Give her a break.

    Furthermore, even if Melanie is ignorant on these things, then as much as you might like to mock that, it does not discredit the science that identifies climate change. It just means that some people are trying to find evidence of it everywhere, including places where it is not. It does not mean that the places where the evidence is strong, is suddenly forgotten!

  • 11
    stephen martin
    Posted Thursday, 1 October 2009 at 3:46 pm | Permalink

    Mark no indeed, although your piece came just before mine I had not not seen it at the time. It is nice to hear from experts, particularly those as well qualified as yourself. It did answer a couple of points that I raised - thank you.

    As far as the La Paz quake was concerned I mentioned it only from interest, I certainly didn’t intend that that I thought there was a link.

  • 12
    Robert Barwick
    Posted Thursday, 1 October 2009 at 4:22 pm | Permalink

    Jim: Mark Duffett hit the mark when he said that there’s a “troubling general ignorance of how our planet works”. Whether it was Melanie Mahoney for herself, or on behalf of others, the question indicated exactly that. Climate change hysteria wouldn’t be so widespread if there wasn’t such a general ignorance, and I suspect the hysteria could be contributing to the general ignorance, by the way people are encouraged to look for the impact of climate change in everything that happens.

  • 13
    meski
    Posted Thursday, 1 October 2009 at 4:29 pm | Permalink

    The other thing, apart from the general ignorance, is that a lot of the arguments are of an appeal to authority nature. This is fine as far as it goes, but as Wiki notes:

    ” The fallacy only arises when it is claimed or implied that the authority is infallible in principle and can hence be exempted from criticism.”

  • 14
    Mark Duffett
    Posted Thursday, 1 October 2009 at 4:31 pm | Permalink

    FWIW, I meant ‘general’ as in ‘general public’.

  • 15
    Pete WN
    Posted Thursday, 1 October 2009 at 6:31 pm | Permalink

    Robert, I think you need to show a little more respect to Interns. Its a ‘Crikey Clarifier’, so it makes sense that any hint of a link between climate change and the Earthquakes is ‘clarified’; particularly given the number of extreme natural events that have been in the press recently, which do (arguably) have links to climate change.

    In this light, I thought it was a reasonable question (even though the answer seemed obvious). It certainly wasn’t “an absolutely goddamn moronic thing to ask”. Ouch, man.

  • 16
    Tamas Calderwood
    Posted Thursday, 1 October 2009 at 7:10 pm | Permalink

    Could this be at all related to the effects of climate change?

    Well, maybe. The planet has cooled by about 0.1C over the past 11 years so maybe this ‘climate change’ has effected plate tectonics and caused all those other “extreme natural events” Pete WN refers to.

    Or then again, maybe not.

    Also: “Other earthquakes though “may be related [to climate change]. If, for example, the polar ice caps melt you get more water in oceans or more weight in some places or pressure released in some places” which can cause plates to shift and earthquakes to occur.”

    Hmm… that’s a mighty big “”if” and I don’t see a skerrick of evidence for it. But we don’t need evidence in the climate change debate because we have hyperbolic dooms-day assertions instead.

  • 17
    Yuwalk
    Posted Thursday, 1 October 2009 at 9:29 pm | Permalink

    Its called google Tamas. Plenty of evidence.

    http://www.seis.com.au/Basics/Dams.html

  • 18
    Mark Duffett
    Posted Thursday, 1 October 2009 at 11:19 pm | Permalink

    Stephen, no worries. It was the media (the ABC in this instance) I was having a go at, not you.

  • 19
    Jim Reiher
    Posted Friday, 2 October 2009 at 1:25 pm | Permalink

    No evidence for climate change? Is that what you really believe Tamas? What are you NOT reading?

  • 20
    meski
    Posted Friday, 2 October 2009 at 2:13 pm | Permalink

    Could this be at all related to the effects of climate change?”

    It was humour.

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