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Watching Earth's convulsions from space

Jonathan Amos | 22:55 UK time, Friday, 24 September 2010

One of the most impressive applications of satellite technology is the now-routine observation made from space of earthquakes.

I've posted previously about the "damage maps" [4MB JPEG] that can be made from radar data.

Relief workers use them to guide their activities in a shattered city, such as in Haiti's Port-au-Prince at the beginning of the year. But radar satellites are also used to study the shifting geological faults that give rise to these catastrophic tremors.

One of the most fruitful areas of research in the past 20 years has come from the use of Sar Interferometry (InSar).

Interferogram of New Zealand

The 4 September quake in New Zealand had its epicentre about 55km north-west of Christchurch

It involves combining at least two radar images of the same location on the Earth's surface in such a way that very precise measurements can be made of any ground motion that has taken place between the acquisitions.

In the case of quakes, these will be "before" and "after" images.

Artist's impression of Envisat

The European Space Agency's Envisat is a huge Earth observation spacecraft 

It enables scientists to produce something called an interferogram. Somebody once described these maps to me as looking like the rainbow effect you see on the surface of bubbles. They're certainly very pretty.

The coloured bands, or fringes, represent ground movement relative to the spacecraft. This gives researchers a remarkable overview of how rocks have shifted, and allows them to see phenomena that no amount of leg work at the surface could achieve.

At volcanoes, likewise, interferograms can show the mountains "breathing" as surface rock is pushed from below by rising magma.

"Hot off the presses" is the interferogram I've included at the top of this page revealing ground deformation resulting from this month's Magnitude 7 earthquake in New Zealand.

Scientists have only just started to pick over the information, so there is not yet much to say, but interferograms for previous quakes have given important insights into the true causes of those events and the consequences for future seismic hazard. Professor Barry Parsons is affiliated to the Centre for the Observation and Modelling of Earthquakes and Tectonics (Comet) at Oxford University:

"If you take the Bam earthquake that occurred in 2003, there is a very well-mapped fault - the geologists had been there and known about it for a long time. And immediately after the earthquake, they all rushed out and had a look at it, and they couldn't see very much. It turned out that when we looked at the radar, the fault that had moved in the earthquake was not that fault - it was a completely unknown fault and it was buried; it was not visible at the surface before."

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InSar has become something of a European speciality. Although conceptually devised as a technique in the US, it was only really with the launch of the European Space Agency's ERS satellites in the 1990s that this branch of science really took off.

Today, the key spacecraft for InSar, certainly in a European context, is the mighty Envisat.

Bam interferogram

The Bam interferogram revealed the quake was caused by a previously unrecognised fault

This eight-tonne behemoth is responsible for producing many interferograms, including the Bam image you see on this page (the NZ image comes from Japan's Alos sat [update:25/09/10]), and its data supplies an army of geophysicists right across the Esa member states, and indeed the rest of the world.

But Envisat, launched in 2002, is entering its dotage. And to eke out its remaining thruster fuel to keep it operating until a replacement capability is launched in 2013, Envisat's orbit is going to be allowed to drift slightly from next month.

For all the applications derived from Envisat's 10 instruments this is no big deal, bar one - InSar [6Mb PDF].

To produce interferograms requires the orbit of the spacecraft to be very tightly controlled and unfortunately, that's heavy on fuel. But the Envisat operators have come up with a clever trick.

They can fix a point above the Earth in this more relaxed orbit where Envisat will always come back to, enabling radar images to be accurately overlaid and permitting InSar studies to continue albeit in a very narrow band centred on 38 degrees North. But as Dr Henri Laur, Envisat's mission manager, explained to me this week, 38 degrees North is an important line across the Earth:

"First we have to think to our continent, Europe, and here we have Italy and in particular central-south Italy. 38 degrees is exactly Etna, which is certainly one of the most studied volcanoes in the world; and Vesuvius is not far away. It also covers Greece and Turkey, which are the most tectonic places in Europe. Going to the east, we cover northern Iran, part of China and Japan. And then in North America, we can see the northern part of California and San Francisco.
"We will have an excursion of plus or minus four degrees over three years. So we will have an eight degree band which will be good for InSar."

For the future, InSar studies will get a big boost when Envisat's radar replacement mission, Sentinel-1 gets into orbit. And, in fact, there'll be two of them, Sentinel-1a and 1b, returning more data, more frequently than Envisat is capable of doing right now.

Envisat Asar antenna

Envisat's UK-supplied radar instrument has made a major contribution to InSar science

As impressive as all this is, there's a bit of a sad story here for British space enthusiasts.

You see, the UK played a leading role in the development and construction of Envisat.


Sentinel-1a is expected to get into space in late 2012 or in early 2013

Its magnificent radar instrument, Asar, which delivers all these interferograms was produced in England. But the UK will not be producing Sentinel-1 because the government decided not to put the required funds into the project -  though it has probably invested something like 750 million euros in the Envisat programme down the years.

So despite Britain having the heritage and the expertise, and despite UK engineers doing the early design work on Sentinel-1 - the job of building the new spacecraft has been handed to Italian and German industry.

Only the central radar electronics subsystem will come from the UK.

And it should be remembered that the Sentinels are a recurring series - as well as 1a and 1b, there will be a 1c, 1d, 1e, 1f, and so on.

Long-term, these contracts will be worth hundreds of millions of euros; and assuming there is no massive foul-up, all this work will continue to be given to Italy and Germany.


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  • 1. At 09:22am on 25 Sep 2010, studentforever wrote:

    Typical of arts educated politicians and civil servants.

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  • 2. At 11:36am on 25 Sep 2010, BobRocket wrote:

    Fascinating pictures Jonathon, given that they can 'see' northern California, does this mean that they can 'see' the so called Super Volcano at Yellowstone ?
    Perhaps the funding bods have already had access to those images and figure that there is not much point in investing in more satellites as they wouldn't be able to 'see' through the ash cloud :)

    Sadly I agree with #1, they spent a huge amount of money to prove the usefulness of the technology only to let it drift off abroad when it comes to actually exploiting that knowledge, led by monkeys we are.

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  • 3. At 1:39pm on 25 Sep 2010, Peter Dunn wrote:

    Very interesting, but I didn't think sound travels in space.
    How does Envisat "eek out its remaining thruster fuel"?
    Does it sound like a balloon being squeezed?

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  • 4. At 3:28pm on 25 Sep 2010, Aldebaranian wrote:

    #3: I am not sure what you think about when you mention sound: A radar uses electromagnetic waves, not sound waves (which is used by a sonar).

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  • 5. At 4:51pm on 25 Sep 2010, Reg Godfrey wrote:

    Do not forget that when the big submarines start to move,they will be visible to these radars as well.

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  • 6. At 5:24pm on 25 Sep 2010, BluesBerry wrote:

    Okay, I'm impressed with all these fancy gadgets.
    "One of the most impressive applications of satellite technology is the now-routine observation made from space of earthquakes."
    Great, does the routine observation separate man-made earthquakes from natural earthquakes?
    "Radar satellites are also used to study the shifting geological faults that give rise to these catastrophic tremors."
    Can these radar satellites study the geological implications of instruments like HAARP (High Frequency Active Auroral Research Program)?
    "It involves combining at least two radar images of the same location on the Earth's surface in such a way that very precise measurements can be made of any ground motion that has taken place between the acquisitions."
    Great, does the routine observation separate man-made earthquakes from natural earthquakes?
    In the case of quakes, these will be "before" and "after" images.
    Can these “before” and “after” images tell us whether the earthquake was man-made, as in HAARP?
    "It enables scientists to produce something called an interferogram."
    Can these interferograms detect HAARP behavior, tell you at which country the destruction is aimed?
    At volcanoes, likewise, interferograms can show the mountains "breathing" as surface rock is pushed from below by rising magma.
    Great, does the interferogram differentiate man-made volcanic activity vs HAARP?
    The Bam interferogram revealed the quake was caused by a previously unrecognised fault – previously unrecognized because it was not there until HAARP put it there?
    I’m really interested in an instrument that can detect (perhaps stop) man-made interference with the ionosphere.
    The individuals who are demanding answers about HAARP are scattered around the planet. They include: independent physicists in the United States.
    HAARP Boils the Upper Atmosphere. HAARP will zap the upper atmosphere with a focused electromagnetic beam. It is an advanced model of an "ionospheric heater." (The ionosphere is the electrically-charged sphere surrounding Earth's upper atmosphere. It ranges between 40 to 60 miles above the surface of the Earth.)
    The electromagnetic waves then bounce back onto earth and penetrate everything - living and dead.
    HAARP publicity gives the impression that the High-frequency Active Auroral Research Program is mainly an academic project with the goal of changing the ionosphere to improve communications FOR OUR OWN GOOD. BUT US military documents put it more clearly - HAARP aims to learn how to "exploit the ionosphere for Department of Defense purposes."
    HAARP can cause earthquakes, volcanoes, landslides, interfere with normal weather patterns…For the life of me, I don’t know why weather people, scientists, climate folk aren’t demanding more access and inspection of the HAARP facilities. HAARP is a weapon of mass destruction. E.g. Was HAARP involved in Haiti quake? Was HAARP involved in Pakistan floods?
    As far back as 1966, Professor Gordon J. F. MacDonald was associate director of the Institute of Geophysics and Planetary Physics at the University of California, Los Angeles, was a member of the President's Science Advisory Committee, and later a member of the President's Council on Environmental Quality. He published papers on the use of environmental-control technologies for military purposes.


    So, are we more interested in watching earth's convulsions from space, or ascertaining the cause(s)?

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  • 7. At 5:26pm on 25 Sep 2010, me wrote:

    These post-event results demonstrate the powerful method that is used.
    If however pre-event bulges could be detected, then we would have a
    chance to issue warnings, with sufficient lead-time to enable
    evacuation, and the saving of many lives.

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  • 8. At 6:01pm on 25 Sep 2010, peddytheviking wrote:

    #4: Can't you see the pun?

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  • 9. At 6:42pm on 25 Sep 2010, geoff hayton wrote:

    I thought that the Single market didn't allow contracts to be awarded to specific countries, so how come the satellite work will go to Italy and Germany?

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  • 10. At 6:48pm on 25 Sep 2010, dividebyzer0 wrote:

    Radar could also monitor changes in ice at Glacial, Arctic / Antarctic locations. (with Satellite in a polar orbit.) I'm surprised this was not put to use earlier as they have the same problem. Has any ice melted? or did it just move from point A to B?

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  • 11. At 7:47pm on 25 Sep 2010, pks wrote:

    #4 Seems you missed the spelling mistake which #3 picked up on. "eek" (in the article) is a squeaky noise. "eke" is when you make the most of the little that's left - which is the word that the article should have used.

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  • 12. At 8:10pm on 25 Sep 2010, Aldebaranian wrote:

    #8 & #11: (Sound of forehead being slapped forcefully) - ok, I'm now feeling pretty stupid :) Thanks for bringing a rather sheepish smile to my face! #3: Sorry!

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  • 13. At 8:14pm on 25 Sep 2010, The Toothbrush Man wrote:

    I used to work on the ERS-1 and ERS-2 programs, and my own speciality was indeed Interferometric SAR. I left the industry before ENVISAT came online. It broke my heart to do so.

    Monitoring of glaciers and ice fields with InSAR has been going on for decades. You can see glaciers slip into the sea and measure their speed. It's all very impressive.

    When engineering an orbit, true pole-to-pole orbits tend to be avoided. This is because an orbit slightly tilted over by a few degrees will precess, which is handy because you can get the rate of precession to match very closely the rate at which the Earth goes around the sun. Why ? because you can maintain a constant attitude of the satellite towards the sun which is useful if you need to charge batteries with solar cells. But tilting the orbit off a true pole-to-pole orbit means that a circular area close to the poles will never pass underneath the satellite and will never be imaged.

    InSAR has been used in all sorts of places. My favourite was to locate subsidence from mining in Eastern Europe - mines would collapse and houses fall into them. You could see the ground gradually shifting. It's the same principle for volcanoes.

    "Do not forget that when the big submarines start to move,they will be visible to these radars as well."

    Depends. SAR (not InSAR) in general is good for finding even small ship wakes, and from the geometry, the speed and direction of the ship can be determined. But a submarine far underneath the water is quite undetectable by SAR.

    I am surprised the article didn't mention the common problem with InSAR from satellites. You need at least three SAR images to compare - and the relative position of the satellite when the images are captured need to be only about 10 - 50 metres apart. You might need to wait a minimum of 24h before the satellite can do so (usually a few days), and during this
    time the ground MUST stay absolutely stationary. And I mean REALLY stationary - a leaf turning over, a large insect moving, anything will ruin the pixel in the interferogram. This is a tall order. Hence InSAR only works in areas that do not change - like deserts, dry rock and snow fields. This is why InSAR does not work over the sea, over grassland or forest.

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  • 14. At 9:17pm on 25 Sep 2010, stillalert wrote:

    Three questions:
    --- One of the interferograms in the article shows a 2-mirror symmetry --which of the two directions is the fault-line?
    --- Can slip-direction on the fault be inferred, whether steep or horizontal?
    --- How does the alignment and type of the 'new' fault compare with the known, mapped one?
    ...(and much more...)

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  • 15. At 9:17pm on 25 Sep 2010, HumbledByNature wrote:

    Thanks for this great (but very depressing) article Spaceman!

    When I started my career as a junior engineer in the space industry I was involved in the early work on Sentinel-1, it was fascinating. During this time, I was proud to be working alongside some of the guys that worked on the original Envisat and its ASAR.

    The funding disaster for Sentinel-1 was totally devastating; we were in prime position for this mission, the expertise and experience was there – then out of nowhere it all fell to pieces, it was taken from us. I don’t really know exactly what happened at the Govt. level, but what is certain is that WE (the UK) CANNOT ALLOW ANYTHING LIKE THIS HAPPEN AGAIN. EVER. I hope that people in the UK Space Agency confront this and think very carefully about how potentially fragile the space industry can be. It needs to be nurtured and allowed to blossom – then we shall reap the rewards a hundred-fold.

    But let’s not dwell on past mistakes. The UK space industry seems as strong as ever at the moment and, providing the govt doesn’t make any colossal mistakes like this again, it will be the future.

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  • 16. At 10:28pm on 25 Sep 2010, ghjklzxcvb wrote:

    It's not just SAR, the British designed & built ATSR series of instruments which has been monitoring sea surface temperature since the early 1990s will be replaced by an Italian and German instrument on Sentinel-3.

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  • 17. At 10:30pm on 25 Sep 2010, Hairy Dan wrote:

    #6: Maybe you should stop believing everything you read on paranoid conspiracy theory websites.

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  • 18. At 10:53pm on 25 Sep 2010, Jonathan Amos wrote:

    @Peter Dunn @Aldebaranian @pks: Thanks for picking up the spelling mistake - it's been corrected. I am indebted.
    @geoff hayton: In the European Space Agency, work tends to get handed out on a geo-return basis called "juste retour". What a country puts into a project financially, it gets back proportionately in industrial contracts. If you don't put in, you don't get back. It's as simple as that. The UK did finally turn up with a lot of cash for the Sentinels programme in 2008, but by then all the major jobs had already been given to other Esa member states. And because this is a part-funded EU programme, the UK will end up paying a lot of money towards these future spacecraft anyway. On the positive side, UK science is very strong in exploiting the data.
    @stillalert: The fault that caused the grief in Bam runs down the middle of the "butterfly". If you want more details, I'm pleased to see the original Geophysical Research Letters paper which detailed all this is now freely available online here. It explains how the Nayband-Gowk-Sabzevaran fault system to the west of Bam, which many suspected at the time was the culprit, was not in fact to blame.
    @HumbledByNature: This is now a key test for the new UK Space Agency. In the past, space policy in the UK was focused on the people (gov departments; research councils) who "used" it services, not on the industrial capability that "manufactured the infrastructure" which delivered those services. Can the UK Space Agency marry the two?

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  • 19. At 00:02am on 26 Sep 2010, nioc98 wrote:

    If studentforever has such a low opinion of arts education, perhaps rather than just sneering, it would be better to give us her analysis of why such an education is of such little worth...
    I am not convinced that science, which has gifted us the nuclear bomb, and some very doubtful research into race carried out in Auschwitz and Belsen, is above reproach.
    All academic endeavour is, at its best, a search for truth and excellence. If a project doesn't measure up, then it is right that it fail.
    This applies to politics as much as to academia. Obviously, if a country elects incompetents, whatever their educational background, to promote its scientific output, then it gets the result it deserves.

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  • 20. At 03:01am on 26 Sep 2010, Brad A wrote:

    As an American space enthusiast and aerospace engineer, I think it's great to have the UK and Europe in the game big-time. On the grand timeline, space exploration is still in its infancy. The UK can positively acquire as much of a leadership role as it wants. There is a lot to explore and plenty for everyone. The private sector is a whole new dimension. Exciting times!

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  • 21. At 05:00am on 26 Sep 2010, Robin_Sal wrote:

    I have a question. Is what is required for the system to work is a third known point in space? The US had left a corner prism on the moon. We can locate it's precise location from the earth. We may also have points in space from the GPS satellites. Could these be a reference point?

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  • 22. At 05:35am on 26 Sep 2010, onefeather wrote:

    I agree with BluesBerry

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  • 23. At 05:43am on 26 Sep 2010, GordonDR wrote:

    studentforever: on the contrary. The bean-counters care even less for supporting the arts than for supporting science.

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  • 24. At 4:48pm on 26 Sep 2010, Petroglyph wrote:

    The Toothbrush Man might be interested to know that the use of interferometric SAR isn't quite as restrictive as he suggests - it all depends on the radar's frequency and the dominant scattering process.

    For example, interferometric SAR can be used to estimate forest biomass as at long wavelengths (L- and P-band) a radar beam penetrates the canopy and the interacts with tree structures and the ground (whereas at X-band the energy is scattered by the leaves). The gap between the successive images needed to generate the interferogram and estimate tree height can be days or even weeks as trees don't grow that fast!

    Unfortunately, there are some atmospheric effects which affect SAR at long wavelengths, which means that it is necessary to transmit and receive in both horizontal and vertical polarisations. Nevertheless, P-band polarimetric InSAR is seriously being looked at as technique for measuring global biomass.

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  • 25. At 1:22pm on 27 Sep 2010, mark-dj wrote:

    @6 BluesBerry: Could you tell me exactly how ionospheric experiments can cause "earthquakes, volcanoes, landslides"...and "interfere with normal weather patterns"?

    As #17 says, you should probably stop believing everything you read on paranoid conspiracy theory websites, but you should probably also stop reading science blogs, seeing as you clearly aren't interested in science. I'd have recommended you stick to watching Doctor Who, but even that's probably a bit fact-heavy for you.

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  • 26. At 5:41pm on 27 Sep 2010, Greg Dance wrote:

    Amazing lot we British!

    We have some of the worlds brightest and most motivated scientists and engineers producing world class technology such as the radar for this satellite and many innovative technologies before it. We also invent the best leisure games (golf, cricket, football, tennis etc) then we just sit back and let the world make fame and fortune from our ideas.

    Anyone know why for certain, I'm stumped!

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