Skip to Content

Collaboratively Answering Australia’s Geoscience Questions.

Geodesist Gary Johnston on where maths and Earth meet

Recently, long-term AuScope collaborator, Gary Johnston of Geoscience Australia won a Queen’s Birthday award for outstanding public service in national and international satellite positioning and geodesy. We uncover this humble scientist’s passion for geodesy (where maths meets Earth), journey with AuScope from the start, and sizeable feats for positioning in Australia.

How did you become interested in Earth Science?

I grew up in a farming community in bushy Brogo, NSW and loved life in the great outdoors. At school, I discovered that I was good at mathematics and then became interested in surveying.

I studied at the University of Canberra and found work as a graduate with the Australian Surveying and Land Information Group (AUSLIG, now Geoscience Australia, GA) in Darwin. There I was involved in large-scale boundary surveys for Aboriginal land claims, and was struck by geodesy– the branch of mathematics which deals with the shape and measurements of the earth, or large portions of it.

In 1993, I transferred back to Canberra to work on the geocentric datum of Australia (GDA94)–
my introduction to the Global Positioning System (GPS) and geodesy, at the University of Canberra. Soon after I joined GA’s geodesy program. I went on to work in Global Navigation Satellite System (GNSS) and GPS analysis, Antarctic geodesy, and GPS network development, and eventually became section leader of the National Geospatial Reference System (NGRS) project.

Around that time, the National Collaborative Research Infrastructure Strategy (NCRIS) emerged as a possible way to fund research infrastructure. Together with Dr. Barry Drummond, Dr Phil McFadden, Prof. Kurt Lambeck and others, we identified the need for major infrastructure investment to achieve the high-powered national geospatial reference system to support Australian industries, and along came AuScope – the perfect vehicle.

What are you working on right now?

I’m currently head of the newly formed National Positioning Infrastructure (NPI) branch at GA.
Our team is tasked with implementing Australia’s national geodesy program, and the two new positioning budget measures: the first on a Satellite Based Augmentation System (SBAS) and second on enhancements to Australia’s NPI capability, which significantly extends the existing GNSS capability (including AuScope infrastructure).

I am also Chair of the international GNSS service, which Is a scientific service under the International Association of Geodesy (IAG), I also co-chair of United Nations Global Geospatial Information Management Sub-committee on Geodesy, which aims to enhance the accuracy and sustainability of the global geodetic reference frame for the betterment of society.

Can you share a happy accident or turning point in your work/research?

After 1994, I embarked on a dramatic career change from boundary surveying to geodesy,
which ultimately led me to become Australia’s chief geodesist, and chair of national and international committees which benefit our nation.

You recently won a Queen’s Birthday Public Service Award, congratulations!

Yes, I was very honoured to hear I’d been nominated, and very surprised, because I’m just doing my job! But it is very gratifying to be acknowledged by our community for the work I’ve done over an extended period.

Do you have an analogy that helps people understand what you do?

Well, everything happens somewhere. Geodesy is about establishing a reference frame with which we can measure where everything is, and more recently with advances in technology, it is about delivering that ‘where’ in real-time.

What is the biggest misconception about your work or field that those beyond it have?

That accuracy of positioning is not all that important. But as society continues to develop we see that needing to know where you are, with a higher and higher level of accuracy, becomes more and more important. Particularly where that knowledge is used to drive automation.

We also need to monitor our planetary system to far better understand how it is changing through time, and what impact we’re having on it. I.e. anthropogenic science. For example, we need to be able to monitor surface subsidence due to oil, gas and water extraction, and the effect that it can have on the stability of the Earth (faults and earthquakes). Often these are occuring all in the same area such as in Gippsland, Victoria, so it’s critical that we know where and how these factors affect the environment.

How is your current work important in the real world?

It is important for efficiencies, safety and environmental management in a whole suite of industry sectors (mining, shipping, agriculture, environmental monitoring, hazard monitoring etc.) which can be enhanced by accurate and high integrity positioning.

How, and to what extent does your work depend on AuScope?

AuScope has been a very effective mechanism for us to develop research infrastructure. The AuScope investment has demonstrated both the value of the geodetic infrastructure to Australia, and also the flow-on research programs that can come from such investment. Both are now starting to produce great value for our society.

What are you most passionate about in geodesy?

I love geodesy because of the strong connection to science, it’s about understanding the Earth as a whole and how it changes through time. I love the large sense of scale in the field.

But I’m most passionate about communicating the value of positioning capabilities to countries that are less well placed than Australia, so that they can enjoy the economic, safety and environmental benefits that can come from geodesy.

What inspires you outside of geodesy? What single question would you like answered in life?

I’m inspired by the life my parents lived. I’m not sure I could wrap all of my questions about life into a single question.

What are the big challenges and opportunities ahead in Australian geodesy?

As geodesy advances and accuracies improve, it becomes more complex for users – this is the challenge. But the opportunity lies with new ways of thinking and working, for instance the Internet of Things, with new mobile sensors: low cost positioning is becoming prevalent and will drive the mass uptake of advanced positioning in Australia.

Who would have thought that our phone positions will be accurate to within ten centimetres anywhere in Australia and its maritime zones? Within the foreseeable future you will be able to travel safely through downtown Melbourne or into the bush in a driverless car.

What’s it’s like to work in the Australian geoscience research community?

I like that geodesy is a global science, and that the Australian community is strongly integrated with the global community, take the International GNSS Service (IGS) for example, which contains over 500 people from over 200 global organisations. If there’s something missing domestically in terms of skills, then we can reach out globally. It’s also great that we have a young and actively developing geodetic community here.

Thank you so much for sharing your insights with us!

Is there anything we’ve missed?

Yes, my favourite colour is blue.

If you would like to know more about Gary’s work with AuScope, please visit our Geospatial Program page. If you would like to better understand geodesy, we recommend visiting Geoscience Australia’s geodesy section.

0 0 Continue Reading →

CEO’s Update 29/08/18

Dear AuScope community,

It seems that each time I write one of these I start out by saying what an exciting quarter it has been. That is once again the case! This time though, a quarter punctuated by appreciation of personal achievement, as well as the inclusion of some new faces in the AuScope family.

Let me start by congratulating AuScope collaborator and project leader, Gary Johnston on being awarded the Public Service Medal in this year’s Queens Birthday Honours List.  Secondly congratulations to AuScope board member and CEO of the DETCRC, Professor Richard Hillis on being named South Australian Scientist of the Year. What a fantastic and well-deserved achievement for both of these long-time leaders in the AuScope and broader geoscience communities.

I would also like to welcome Dr Meghan Miller to AuScope. Meghan has taken over from Professor Malcolm Sambridge as Component Leader for the Earth Imaging program based at ANU.  Meghan brings a wealth of international experience and knowledge in field-based seismology to our team and we look forward to working with her on future programs. I would also like to sincerely thank Malcolm for the incredible amount of work he has put into managing these programs over recent years. Malcolm will continue to be involved in some of the AuScope programs at ANU so we will still see him around.

Finally, I would like to take the opportunity to let you all know that we have been working very hard doing the groundwork for our future investment planning process. As part of this we are in the process of undertaking a series of reviews. Preparations are also well underway for the community planning workshop to be held after the AGCC in Adelaide. If you have not yet registered and wish to attend please do so as soon as you can as places are almost filled.

Cheers, Tim

0 0 Continue Reading →

AuScope Discovery Portal 5.0.0 Release

AuScope Grid’s Informatics Platforms team at CSIRO Mineral Resources are proud to announce the release of the completely redesigned, rebuilt and expanded AuScope Discovery Portal.

The AuScope Discovery provides a web based interface for searching and accessing data, information, imagery, services and applications connected to the Grid. It allows users to discover, browse, save, and process geospatial information from Earth science data sources around Australia. Hyperspectral, borehole, global navigation satellite, geodesy, mineral occurrence and geology data are all available through the portal.

In this upgrade the layout has been redesigned using standard web conventions to provide an aesthetically pleasing and familiar look.  The application workflow has also been revised to make selecting and filtering layers more logical and consistent.  The presentation of geoscience feature properties and products has been clarified to allow users to more easily identify the information that interests them.

The technology underlying the Portal has been updated to provide superior performance, reliability and consistency.  This upgrade allows the new portal to be fully responsive creating a productive experience on all devices from desktop PCs all the way down to phones.

In addition to the improvements above many new capabilities have also been added.   Some of the highlights include:

  • Direct integration with the 3D geological model website via the 3D Models data layer
  • The NVCL Analytics component allows users to delve into the content of borehole spectral mineralogical data to reveal details not previously accessible.  Users will now be able to make content based filters on the millions of data points contained within the down-hole data products.
  • Geological Province based spatial filtering.  Users can now target a particular geological province by selecting it and using it as a filter for other layers.

 

For more information on this project please contact Program Director – Dr. Rob Woodcock.

0 0 Continue Reading →

Welcoming ANU’s Associate Professor Meghan Miller to the AuScope team as our Earth Imaging program leader

Associate Professor Meghan Miller comes to AuScope with a wealth of knowledge in global seismology and plate tectonics research. Image: AuScope

AuScope is excited to have Associate Professor Meghan Miller leading our Earth Imaging program from 1 July 2018 as Professor Malcolm Sambridge transitions to managing our Seismometers In Schools national outreach program. Congratulations to you both!

Here, Meghan shares her story, from growing up in North America to studying in the US and Australia, with field studies in Morocco, Indonesia and Timor-Leste in between. We discover her passion for plate tectonics and deep Earth, swag of academic achievements, and ambitions for research innovation in Australia.

Tell us about you, in a nutshell.

There is no nutshell, but here goes!

I’m originally from Canada and grew up and studied an undergraduate and two masters degrees in the U.S.  I began my studies in the seismically active Southern California, but later moved to New York. I went on to work at the US Geological Survey and a software company for a few years, but soon, a research career beckoned.

So, I headed to Australia to pursue a PhD at ANU in Canberra. I then returned to Canada and the US to complete my post-doctoral studies. My PhD focused on the tectonic evolution of the western Pacific subduction zones, then my postdoc focused on seismic imaging of the Caribbean and South American plate boundaries.

In 2009, I became an assistant professor at the University of Southern California, and at the beginning of 2017, I returned as an associate professor in seismology & mathematical geophysics at ANU. Now, I split my time between teaching and research at ANU, and program leadership with AuScope!

What are you working on right now?

My research focuses on understanding the Earth’s tectonic evolution using seismology to understand it. Specifically, I’m interested in investigation into the evolution of plate boundaries, in particular active subduction zones, and cratonic structure which can provide a glimpse into ancient tectonic processes.

Right now, I’m planning a deployment in northern Western Australia and the Northern Territory which complements an ongoing experiment I am running in Timor-Leste and Indonesia.

These new data will greatly enhance the imaging capabilities and allow for resolution across the Timor Sea and further improve on a seismic catalogue for this unique tectonic environment.

Do you have an analogy that explains what you do?

Yes! Think of medical CAT-scans that give us an image of bones in our bodies. As seismologists (rather than radiologists), we use seismic waves (rather than X-rays) generated by earthquakes to image the Earth (rather than our bodies).

A series of cross-sections through the crust and upper mantle beneath Alaska (Miller et al., 2018).

Why is your current research important, and how does it translate to the real world?

I’m studying why and how both the continents and in fact the whole tectonic plates have evolved into their current state. I am particularly interested in plate boundaries where active processes are evidenced by volcanoes and earthquakes. These features affect our lives. If we can better understand why, where and when these Earth processes are most likely to occur, we can best inform the general public and protect lives.

How, and to what extent does your work depend on AuScope?

Without AuScope data, it would be impossible to attain the resolution that we need to produce images of the Earth’s interior that begin to bridge the gap between geological observations and geophysical observations.

What is the coolest thing about your job?

Being able to travel to remote locations and see the world from a different perspective, and also see the diversity in landscapes and geology and as well cultures and environment.

Exploring a volcanic landscape on the Aeolian Island of Vulcano in Italy, which is a research area of interest Meghan’s my studies of subduction zone evolution and links to volcanic processes. Image: Associate Professor Meghan Miller

Can you share a happy accident or turning point in your research?

One of the first field experiments I conducted was in Morocco and Spain, where I was investigating seismic activity along a subduction structure at the plate boundary. I laid out seismometers in the Atlas Mountains, south of the plate boundary, and found links to volcanism unrelated to subduction zone, rather, likely a mantle plume below the Canary Islands that had channelled up in my field area.

What’s it’s like to work in the Australian geoscience research community?

In the states and Canada, the seismology community is relatively large. Here, you get to know people quite well and have access to lots of resources for research, such as AuScope. Australia has a large influence on the global science community as it so far away, but is focussed on international collaboration, it’s nice to be a part of that.

How do you see your field developing in the future?

In order to gain greater insights into large-scale earth processes, our field needs masses of data at much finer geographical spacing than have been collected historically.

Right now, we have new capabilities in seismic instrumentation called ‘nodes’, which are soup can-sized, battery operated and cordless.They can be placed at just a few tens of metres apart, rather than hundreds of kilometres, allowing ‘large-N’ experiments to be conducted. With these new instruments and data handling capabilities, we can collect high density data that are no longer aliased spatially.

In my AuScope role, I look forward to further bridging the gap between geophysical and geological observations, alongside AuScope Earth Imaging collaborators at Australian National University, the University of Adelaide, The University of MelbourneGeoscience Australia and state geological surveys.

Learn more about our Earth Imaging Program

0 0 Continue Reading →

AuScope Strategy Workshop 2018

AuScope is excited to lead a Strategy Workshop on its current and future programs at the National Wine Centre of Australia in Adelaide between 18 – 19 October 2018. The event will include two parts, a Working Dinner on Thursday 18 October, and the Strategy Workshop on Friday 19 October. Community members and future collaborators, please join us in building the future of Australian geoscience research.

Overview

Here, we will provide current and future collaborators with an opportunity to:

  • Learn about AuScope’s charter, funding mechanism, and funding opportunities
  • Reflect on national geoscience priorities of the Decadal Plan for Australian Geoscience
  • Learn about AuScope’s current infrastructure (tools, data and analytics) programs and projects
  • Collectively ideate and discuss potential, collaborative AuScope programs and projects

With Australian research infrastructure faring well in the 2018 Federal Budget ($1.9B over 12 years), AuScope and our NCRIS peers are set to benefit enormously from both the sum and period of this funding, as are all Australians whose lives and environment are positively impacted by research innovation.

It is now critical that our Australian Earth and Geospatial research community responds to both known (and unknown) infrastructure funding opportunities (and limitations) with AuScope in the decade ahead, with consensus, and with Australia’s geoscience challenges front of mind.

Waiting List

This event is now at capacity. Please leave your details here and we will be in touch if a place becomes available.

Communications

If you cannot attend

If you cannot attend, but would like input into the process or to receive updates from us, please sign up here.

0 Continue Reading →

Australia races towards futuristic location-based services with high-precision positioning technology

There’s already been one revolution in navigation over the past couple of decades, with the change from printed maps to satellite navigation. Now there’s new technology on the way that will further transform the way we position ourselves on the globe.

In 2017, Western Australia’s growers harness precision agriculture in on-farm trails that use GPS technology. Soon positioning technology will become accurate to within ten centimetres or less nationally– a stepwise gain in agricultural optimisation. Image: Get Regional

With today’s satellite navigation technology we have the ability to access positioning information at the touch of a button, from in car navigation systems to smartphones and activity trackers on our wrists.

With help from AuScope, the next generation of positioning technology will accelerate new and innovative uses of positioning information – many of which are yet to be imagined.

A big leap in accuracy, availability, and reliability is being made available free across Australia, thanks to the Australian Government’s commitment in Budget 2018-19.  The investment of $224.9 million will allow Geoscience Australia to develop world-leading positioning capabilities that will help shape the future of industry and business in Australia.

Geoscience Australia will dedicate $160.9 million of that investment to develop an operational Satellite Based Augmentation System, commonly known as SBAS. An SBAS will deliver corrected positioning signals, such as that received from GPS, directly to the user through satellite technology, improving the accuracy, availability, and reliability along the way. An SBAS will ensure reliable positioning data accurate to 10 centimetres is available throughout Australia, including its maritime jurisdiction.

Schematic diagram of SBAS where positioning accuracies of 10 cm will be available across Australia, providing a world of possibilities for new technologies. Image: Geoscience Australia

The remaining $64 million is dedicated to upgrading Australia’s Global Navigation Satellite Systems, GNSS network through the National Positioning Infrastructure project. The project will establish the necessary ground infrastructure to enable data from global networks of satellites to be tracked, verified and optimised for precise positioning with an accuracy of three centimeters across Australia in areas with mobile coverage.

Together these projects aim to build an integrated and interoperable capability that will provide instant, accurate and reliable positioning information for all Australians anytime and anywhere across our nation.

The majority of Australians can only position to 5 metres accuracy with current technology. In the near future, the NPI will provide accuracy of 3cm in areas with mobile coverage, enabling emerging innovation such as semi-autonomous vehicles to enter existence. Image: Geoscience Australia

Breakthrough

Today, accurate positioning technology requires dedicated equipment with the right hardware, software and communication links – and this is expensive.

Australia stands to benefit significantly from building upon the hundreds of ground stations that have been installed across Australia by private industry, and federal, state, territory and local governments.

AuScope Geospatial played a key role in the development of this infrastructure, with a critical injection of funding and establishment of the framework under which Geoscience Australia has worked with state and territory governments to build world-class GNSS infrastructure. This includes a network of over 100 GNSS ground stations and the systems and tools to deliver data to the science and research community.

Dr. John Dawson at Geoscience Australia describes the critical nature of AuScope’s GNSS infrastructure for the positioning program, which government and industry have become really excited about:

“The AuScope GNSS network will be an integral part of the NPI project, contributing to an interoperable network of ground stations across Australia. This network will help enable centimetre accurate positioning which is essential for a wide range of applications, now and into the future”.

The AuScope GNSS network will be used to observe signals from the GNSS satellites for Geoscience Australia to analyse and compute corrections which can be utilised by the user.

“We knew there would huge benefits from positioning technology, but we didn’t realise how quickly we’d be in the position where, not only can we make corrections to achieve greater accuracy, but will be able to provide decimetre accuracy across the whole of Australia,” explains Dr. Dawson.

Using the accurate positioning data from Geoscience Australia, commercial providers will be able to value add and provide additional capabilities for their customers.

Impact on industry sectors

Improving Australia’s positioning capability is more than realising driverless car technology and improving location services on a smartphone, Dr. Dawson says:

“It’s about helping farmers reduce costs and waste, enabling the Royal Flying Doctor Service to land in adverse weather conditions, making it easy to dock a cruise ship in a busy port like Sydney Harbour, and improving safety on construction and mining sites.”

The future of driving was on show at the 2017 Melbourne Grand Prix Circuit, as VicRoads tested a highly automated driving (HAD) vehicle fitted with world-first satellite positioning technology. Image: Bosch via Business Insider Australia.

The technology will help grain growers to control sowing and harvesting along accurately guided tracks – maximising the cropping area and increasing yields.

In mining, positioning technology is already used extensively for activities right along the production chain, from surveying sites to extracting ore and transporting it.

‘In Perth, the mining company Rio Tinto has a central hub where the staff are operating trucks, trains, conveyor belts and transporting mining ore, all behind a computer screen using positioning technology,’ Dr. Dawson said.

Image: Alexandra Pugachevsky via Wikimedia Commons

In construction, this technology is used for site surveying and machine guidance.

And in research, highly accurate positioning allows geodesists to monitor changes in movement of the Earth’s crust, which tells us about the rate of plate motion, stress build up and even seasonal changes in the groundwater.

Location-based services is a market that is anticipated to grow significantly with accurate and reliable positioning technology. For example, positioning technology will transform the way we will locate underground utility services. In future, by standing with a smartphone or tablet at a building site, you could identify exactly where underground pipes or cables are located.

Background

There are six global navigation satellite positioning systems, operated by the United States, Russia, Japan, the European Union, China, and India. Together these systems have more than 80 satellites orbiting the Earth. Australia is one of few countries that can receive positioning signals from all six systems.

Schematic showing the six global satellite positioning systems, which together have more than 80 satellites orbiting the Earth. Image: Geoscience Australia

Each satellite transmits information about its position and the current time. The signals are picked up by your receiver, such as a smartphone or car navigator. The receiver calculates how far away each satellite is based on the time it took for the messages to arrive. Using the location of at least four satellites and their distance from you, the receiver pinpoints your location.

But small errors creep into the measurements made by the navigation receiver. There are several causes, including a slight slowing of radio waves through the ionosphere, variations in satellite timing and variations in satellite orbit.

Even accounting for these errors, existing systems identify a user’s location with an accuracy of five metres.

That is the system used today in car navigation systems and in smartphones.

By correcting these errors, Geoscience Australia will significantly improve the accuracy of satellite positioning in Australia.

It will achieve this through, two projects – SBAS and the NPI project.

This article was written by ProofPoint Advisory consultant, Robert Garran, and edited by AuScope communications and Geoscience Australia.

0 0 Continue Reading →

Endless volcanic eruptions like Jupiter’s Io for early Earth?

There is a mystery in Earth’s ancient past, and the clues lie in ancient cratons of Australia and other places. What was the Earth like before the plates formed? AuScope’s Simulation and Modelling team led by Prof. Louis Moresi have a new theory.

The following article was originally published on Prof. Louis Moresi’s website and adapted for The University of Melbourne’s Pursuit article.

Recent models of the very early Earth showed that the planet could have been cooling rapidly by heat-pipe volcanism (just like Jupiter’s moon Io). Image shows the May 1954 eruption of Kilauea Volcano in Hawaii. Credit: J.P. Eaton, May 31, 1954 [Public domain], via Wikicommons

Cratons are anomalously-strong regions of the continents that have largely resisted tectonic forces for billions of years. How such strong zones could be forged in a hot, low-viscosity, low stress, early-Earth has been a long-standing puzzle for geologists. Adam Beall, Katie Cooper and I have recently proposed that cratons were made by the catastrophic switching on of plate tectonics. An event in which the stresses were larger than they have ever been in the intervening 3 billion years (Beall et al, 2018).

Background

The theory of plate tectonics describes how rigid plates move on the Earth’s surface but this really only applies to the oceanic plates. The continental crust is generally a great deal weaker and can crumple or stretch in response to movements of the oceanic plates forming mountain belts, rifts and low-lying basins.

Some of the oldest parts of the continental crust are an exception to this generalisation. These are regions that have experienced very little tectonic deformation in several billion years of existence. These cratons are thought to represent regions of greater strength and this contributes to their longevity. There is evidence that the deep lithosphere is as ancient as the crust and is anomalously thick and buoyant (e.g. Jordan,1975, O’Reilly et al, 2001, Cooper et al, 2013, 2016). We also think that the cratons formed from cool, thin lithosphere in the time before plate tectonics began and then thickened and strengthened to the point where they became effectively indestructible.

The problem with this idea has always been to explain how the hot, weak interior of the young Earth could generate enough stress to thicken strong lithosphere. Alternatively, if the lithosphere was weak too, what stopped it from falling apart by gravitational spreading while it cooled and ‘hardened’?

(A) Map of the Archean Cratonic crust (dark blue) identified from the Crust 1.0 and paleoproterozoic crust in pale blue. (B) A map of the relative thickness of crust to lithosphere (also from Crust 1.0) which tends to pick stable zones in blue shades from deforming zones in red.

New views

Recent models of the very early Earth showed that the planet could have been cooling rapidly by heat-pipe volcanism (just like Jupiter’s moon Io). Massive volcanism is enough to prevent plate tectonics from switching on, but when the Earth does cool down enough for the eruptions to slow, a catastrophic transition begins. Short, violent pulses of lithospheric foundering and overturn occur before steady plate motions take over (e.g. see Moore & Webb, 2014, Rozel et al. 2017).

We modeled what happens to the strong and buoyant material of the heat-pipe lid during these early-Earth overturn events. We found that the lid was crumpled up into large islands of thick, buckled and very strong lithosphere by the overturn of the cold, thick, stagnant boundary layer. Once the model Earth settled down to a more sedate form of steadily moving plates, the stresses never reached a level that could deform these remnants of the pre-plate-tectonic state.

Snapshots from this movie that show the initial failure of the cold lid after the heat-pipe mode stops (A), followed by repeated sloughing off of the cold boundary layer in (B) and a slow approach to steady state in (C) where the thick, crumpled lithosphere is shuffled around without deformation.

n the figure above, the green and grey stripes were initially horizontal layers at the upper surface of the planet and are folded by the foundering of the thick boundary layer. In these simulations, the boundary layer is shed in less than an overturn time. Each model craton experiences a few, closely spaced, shortening events the create a thick pile of material with intricate internal structures not unlike those seen in seismic images that have been attributed to early subduction (Bostock et al, 1998).

The model cratons form cold and from material that was originally crystallised at shallow depth. The formation is also a time of temperature inversion in the mantle: cool material is dumped at the core mantle boundary resulting in higher-than-average core heat flux. The phase of mobile-lid convection that follows this (analogous to plate tectonics in this kind of model) has high velocities near the surface, thin oceanic lithosphere and low stresses. In this environment the cratons are safe from harm and this remains true to the present day despite lithospheric thickness and ambient stresses gradually creeping higher.

Background Reading

The details behind the work described in this post:

  • Beall, A., Moresi, L. Cooper, C. M. Formation of cratonic lithosphere during the initiation of plate tectonics, Geology, https://doi.org/10.1130/G39943.1, 2017

Papers on the longevity of the deep cratonic lithosphere:

  • O’Reilly, S. Y., W. L. Griffin, Y. H. P. Djomani, and P. Morgan (2001), Are lithospheres forever? Tracking changes in subcontinental lithospheric mantle through time, GSA Today, 11(4), 4–10.
    • Jordan, T. H. (1975), The continental tectosphere, Reviews of Geophysics, 13(3), 1–12, doi:10.1029/RG013i003p00001.

Read about the formation and structure of the ancient continental lithosphere:

  • Cooper, C. M., A. Lenardic, A. Levander, and L. N. Moresi (2013), Creation and Preservation of Cratonic Lithosphere: Seismic Constraints And Geodynamic Models, in Archean Geodynamics and Environments, vol. 164, pp. 75–88, American Geophysical Union, Washington, D. C.
  • Cooper, C. M., M. S. Miller, and L. Moresi (2016), The structural evolution of the deep continental lithosphere, Tectonophysics, 695, 1–89, doi:10.1016/j.tecto.2016.12.004.

Heat pipe models of the early Earth:

  • Moore, W. B., and A. A. G. Webb (2013), Heat-pipe earth, Nature, 501(7468), 501–505, doi:10.1038/nature12473.
  • Rozel, A. B., G. J. Golabek, C. Jain, P. J. Tackley, and T. V. Gerya (2017), Continental crust formation on early Earth controlled by intrusive magmatism, Nature, 545(7654), 332–335, doi:10.1038/nature22042.

The observations of structure in the ancient cratons:

  • Bostock, M.G., 1998, Mantle stratigraphy and evolution of the Slave province: Journal of Geophysical Research. Solid Earth, v. 103, p. 21183–21200, https://doi.org/10.1029/98JB01069.
  • Calò, M., Bodin, T., and Romanowicz, B., 2016, Layered structure in the upper mantle across North America from joint inversion of long and short period seismic data: Earth and Planetary Science Letters, v. 449, p. 164–175, https://doi.org/10.1016/j.epsl.2016.05.054
0 0 Continue Reading →

Seismology collaboration and support in response to PNG earthquake

On Monday 26 February, a major earthquake occurred in the Southern Highlands of Papua New Guinea, with a magnitude of 7.5 and a surface fault rupture length exceeding 100 km. The earthquake triggered many large landslides over a wide area, and resulted in a call for emergency care for around 270,000 people, and tragically over 150 known fatalities plus an unknown number missing. Many aftershocks ensued, with seven exceeding magnitude 6.0 and causing further fatalities.

Aid organisations such as CARE Australia and UNICEF continue to still seek donations.

AuScope’s Subsurface Observatory team was called to participate in Australia’s aftershock monitoring and hazard management response.

Landslides caused by PNG’s magnitude 7.5 earthquake in February 2018. Image: Gary Gibson

The earthquakes occurred along the northern boundary of the Australian tectonic plate, which is moving northward at about 70 mm per year producing the Southern Highlands Thrust and Fold Belt. The epicentral region is very remote, east of Tabubil and southwest of Mount Hagen.

Further north over the western part of PNG there is a complex series of sub-plates through the Bismarck Sea to the southern boundary of the Pacific Plate, with other similar complications in the east of PNG. The Southern Highlands plays a significant part in accommodating the relative motion between the Australian and Pacific plates.

Following the earthquake, AuScope’s Subsurface Observation Project was contacted by the Australian Earthquake Engineering Society. Having already engaged directly with PNG and Australian government agencies, AEES was seeking to assemble a mission to monitor subsequent seismic activity in the region, particularly to record strong motion from larger aftershocks, and to delineate faulting with more precise earthquake locations.

The nearest permanent seismograph providing data to the global network was typically at a distance of 500 to 600 kilometres, severely limiting location accuracy, especially earthquake depth estimates.

In addition to support from Geoscience Australia, Seismology Research Centre (SRC) and the Seismological Society of Australia, AEES were provided with extensive “in-country” assistance, including helicopter access by Oil Search (PNG) Ltd, and support from the Port Moresby Geophysical Observatory. This support proved crucial to the successful deployment of monitoring instruments throughout the region.

Landslides caused by PNG’s magnitude 7.5 earthquake in February 2018. Image: Gary Gibson

Seismologists Gary Gibson (University of Melbourne) and Kevin McCue (Aust. Seismological Centre) planned a temporary seismograph network, with sites north, east, south and west of the aftershock region, plus two within that region. They contacted a number of possible hosts in PNG and selected suitable sites that included a regional hospital, nearby villages and sites within OSL’s oil and gas fields.

Site selection and access was particularly challenging due to the extensive surface disruptions in a steep terrain frequently emphasised by major landslides. Despite the difficult terrain, the team were able to utilise concurrent aid flights, and even managed to locate one of the instruments to within 20km of the apparent mainshock epicentre.

The AuScope Subsurface Observation Project provided six high dynamic range triaxial accelerometers, which are well suited to aftershock monitoring applications. Three high resolution digital recorders were provided by AuScope and three were hired from SRC. To simplify deployment, solar panel power and telemetry of data were not used.

Subsequently, the response team has made a return visit to recover data from the recorders. Aftershock activity has diminished significantly, and some recorders will be removed on the next visit. There is a likelihood of a more permanent array with data telemetry being installed, and local operators are being trained in routine operation.

For more information please contact Gary Gibson.

0 0 Continue Reading →

A new 3D extension for the AuScope Discovery Portal

AuScope Grid’s Informatics Platforms team at CSIRO Mineral Resources have developed a new website extension to the AuScope Portal ecosystem. With this, researchers will soon be able to discover and communicate 3D geological models that have been developed by researchers and government geological surveys of Australia.

Showing the AuScope Portal’s 3D modelling extension.

One of the main purposes of the website is to allow the user to unlock all the information that is held within the model. Not only can the user visually explore the model in three dimensions using WebGL technology, but the data collected as part of the modelling process can be revealed by querying a part of the model. In this way, the user can view borehole data, magnetics or gravity data, for example.

The model links to the AuScope portal and geoscience information services with the user able to, say, follow boreholes into the NVCL to obtain more detailed information about the geology. To complete the set of linkages, the 3D geological model website will be accessible from a data layer within the AuScope portal.

The team is currently working to realise the first part of the project: releasing the website with 3D visualisation capability in beta mode into the AuScope Portal ecosystem in 2018. Stay tuned on Twitter for announcement of its release.

The team will next realise the second part of the project: linking points in 3D space back to borehole data. This represents the main challenge, as borehole data must be first be findable. The team will work with geological surveys and working groups across the geoscience community to ensure that respective data will integrate to facilitate this linkage.

But this challenge also represents most exciting part of the project since it offers the most impact for researchers: a smooth workflow between making interpretations in 3D and then re-interrogating data. The team will undertake this work in the coming financial year, 2018/19.

For more information on this project please contact Program Director – Dr. Rob Woodcock.

0 0 Continue Reading →

Testing new passive seismic techniques in South Australia

In April 2018, ANU seismologists headed to remote northern South Australia to test an exciting proof of concept in seismic surveying: a new and cheaper approach to producing detailed, crustal-scale cross sections of the Earth.

Field crew–left to right: Armando Arcidiaco, Rajesh Erigela, Dr. Michelle Salmon and Geoff Luton at the last seismic station at the eastern end of the array. Image: Dr. Michelle Salmon

Field manager, Dr. Michelle Salmon led the small team of four to install a 230km-long, dense passive seismic line in South Australia from Marla (west) to Oodnadatta (east), with seismic stations approximately every 3.5 km in places following the Oodnadatta Track.

This location targets an area where the team have previously identified a change in crustal thickness in seismic array data, from thick (48 km) at Marla to thin (28 km) at Oodndatta.

Map showing the locations of the seismic array. The Stuart Highway is shown in yellow, the Oodnadatta track is shown in magenta and the seismic stations are shown as blue squares.

The team aims to use seismic signals from both ambient noise and earthquakes to look at the lithospheric structure in detail. They hope that this project will be able to fill the gap between expensive active source seismic lines and larger aperture arrays to provide a detailed crustal scale cross section.

For more information on this project, please contact Dr. Michelle Salmon.

0 0 Continue Reading →