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ACT tech talk: What we can and cannot know from unconstrained inversion of regional magnetic field data

Wednesday, September 27, 2023

Title: What we can and cannot know from unconstrained inversion of regional magnetic field data

Presenter: Clive Foss / CSIRO Mineral Resources

Date and time: 4pm (AEST time), 27th Sep 2023



For many years regional magnetic field data acquired by Geoscience Australia and State and Territory geological surveys has enabled and transformed geological mapping across Australia where many areas are beneath extensive cover and/or pervasive deep weathering. As computing power and availability have increased by orders of magnitude the same data that so successfully supports geological mapping is being re-purposed for building continuous three-dimensional magnetisation models. These models are in some cases accepted by their users in confidence that they are true representations of the subsurface achieved by spectacular powers of computing. However, while aeromagnetic surveys perform extremely well in mapping the horizontal locations and extents of magnetisations, recovery of models of subsurface magnetisation is severely restricted by extensive non-uniqueness. Magnetic field data is so useful for geological mapping because of the dominant expression of shallow magnetisations, in many cases directly beneath a basement unconformity. The sharp curvature of these field variations carries all the reliable information in the magnetic field data. Deeper magnetisations may cause the bulk of amplitude changes in the magnetic field without giving rise to diagnostic curvature of the field. These parts of the magnetisation cannot be reliably assigned to a specific depth or depth range. In space-filling voxel inversions this task is achieved by depth-weighting functions included in the inversion algorithms. It is these functions, not the distribution of magnetisation in the ground, that determine the depth distribution of magnetisation in the models.

I propose separation of features of sharp curvature that carry the most reliable source information (that I term ‘sweet spots’) from the remaining, much less informative field variations. This results in subsurface models that are much sparser in their apparent level of detail. It may seem a negative message, but it is not, because the distilled information can be treated with much higher confidence than continuous models in which it is not clear which aspects can be trusted and which cannot. I use examples of Australian regional magnetic field data to demonstrate analysis and interpretation of sweet-spots suitable for estimation of depth to magnetisation and sweet-spots suitable for estimation of magnetisation direction.      


Clive is a senior principal research scientist in CSIRO Mineral Resources where he works mostly on magnetic field inversion and interpretation. He has a BSc and PhD from two Earth Science departments where he learnt to integrate studies of physics and geology. His particular interest since his PhD (a long time ago) on Archean rocks of Southern Africa is in the magnetic field expression of remanent magnetisation and how direction of magnetisation can be recovered from magnetic field data. After his PhD Clive taught exploration geophysics at the University of Malaya in Kuala Lumpur where living between the geographic and magnetic equators provoked an interest in low inclination magnetic fields. Clive then moved to Bandung to work for the Bureau of Mineral Resources (BMR, now Geoscience Australia) on the AIDAB funded Indonesia – Australia Geological Mapping Project in Kalimantan. Following that Clive returned to Kuala Lumpur to work as a consultant and for ARK Geophysics based in Kuala Lumpur providing services in gravity and magnetic methods for petroleum companies throughout Southeast Asia. In 1995 Clive moved to Sydney, Australia to work with Encom Technology both contributing to the ModelVision development team and acting as senior consultant on gravity and magnetic projects worldwide. In 2009 Clive moved to his present position in CSIRO. 

SEG Distinguished Instructor Short Course (DISC) - Distributed acoustic sensing for seismic measurements – what geophysicists and engineers need to know

Tuesday, September 12, 2023

We are delighted to share with you the details for an upcoming SEG Distinguished Instructor Short Course (DISC) being hosted by the ASEG. 

This course will be run virtually over two days. 


Who: Dr Mark E Willis, Chief Scientific Advisor of Borehole Seismics at Halliburton

What: Distributed acoustic sensing for seismic measurements – what geophysicists and engineers need to know - DISC course

Where: Virtually. There will be a streaming of the virtual course in Brisbane at Anglo-American office, Brisbane, QLD. Please contact if you would like to join the streaming (ensuring that you also register for the virtual DISC)

When: September 12th and 13th 2023, 9am - 1pm ACST each day. 

Cost: $250 USD for SEG and ASEG members which includes access to software and a copy of the accompanying e-book. ASEG members need to use the code emailed to them, or contact Registration cost for non-members is $375 USD.

Register: Please register here by September 12th.


Course description: Geoscientists and engineers are very comfortable using seismic data sets acquired with geophones, hydrophones, and accelerometers because we have a long, well-defined set of standards for acquiring, processing, and interpreting them. However, distributed acoustic sensing (DAS) seismic measurements are rapidly augmenting, and in some cases replacing, the data from these conventional tools. Technologists are frequently unaccustomed to using DAS seismic data sets since it directly acquires relative strain or strain rate measurements and not the more familiar pressure, displacement, velocity, and acceleration data. There are also acquisition parameter selections that must be made to optimize the acquired data to accomplish the purpose of the seismic survey. This course is designed to build an intuition and understanding of the value, limitations, and applications of DAS seismic technology. In addition to the lecture and accompanying book, software will be provided, which will allow the student to interactively explore DAS seismic technology.


For more details visit Current DISC - SEG.

ACT Tech Talk: Scalable Streamlining of Ambient Noise Tomography: A Simple Automated Approach for Dispersion Curve Estimation and Quality Control in the Era of Big Data

Thursday, July 20, 2023

Title: Scalable Streamlining of Ambient Noise Tomography: A Simple Automated Approach for Dispersion Curve Estimation and Quality Control in the Era of Big Data

Speaker: Babak Hejrani

Date/Time: Jul 20, 2023 16:00


Babak Hejrani is a seismologist specializing in the field of geophysics within GA's Onshore Seismic and Magnetotelluric Section. With a decade-long background as a researcher in academia, Babak joined GA in 2018 and has since made contributions to developing new technologies for passive seismic imaging. He has established fruitful collaborations with international organizations in Europe, Asia and Australia with a primary focus around developing and implementing advanced imaging technologies that provide enhanced insights into the lithospheric structure of Australia. Babak strives to push the boundaries of seismic imaging, enabling more accurate interpretations of subsurface features.

Teams meeting:

Microsoft Teams meeting
Join on your computer, mobile app or room device
Meeting ID: 429 910 034 185
Passcode: jbC4ve
Or call in (audio only)
+61 2 8318 0003,,834313932#   Australia, Sydney
Phone Conference ID: 834 313 932#

Induced Polarization effects in Electromagnetic data: opportunity or waste of time?

Thursday, March 30, 2023
1645 (ACT)
1745 (ACT)

Title: Induced Polarization effects in Electromagnetic data: opportunity or waste of time?

Speaker: Francesco Dauti, PhD student at University La Statale of Milan

Date/Time: 30/03/2023 @ 1645

Zoom Registration:


The possibility to model the Induced Polarization (IP) effects from the time-domain Airborne Electromagnetic (TD-AEM) data has gained considerable interest in the last two decades from both industry and academia. 

Recently, it has been physically demonstrated that IP effects can distort AEM data that, if not recognized and properly treated, can lead to artefacts in the modelled resistivities.   What it is still unclear though is if these distortions can be robustly recovered and modelled, providing useful information on polarisation effects within the ground.

Results on two aspects of airborne IP (AIP) modelling will be discussed:

(i) if modelled AIP effects can give significant information for exploration, and

(ii) if it is possible to measure and model AIP in AEM fixed-wing systems.

Francesco Dauti is a Ph.D. student in exploration geophysics at University La Statale of Milan. He took a bachelor’s and a master’s degree at University of Pisa, in geological sciences and in exploration and applied geophysics. His current research field is about the integration of galvanic and inductive Induced Polarization techniques for mineral exploration, both in terms of modelling, inversion, and interpretation.



Francesco Dauti is a Ph.D. student in exploration geophysics at University La Statale of Milan. He took a bachelor’s and a master’s degree at University of Pisa, in geological sciences and in exploration and applied geophysics. His current research field is about the integration of galvanic and inductive Induced Polarization techniques for mineral exploration, both in terms of modelling, inversion, and interpretation.

ASEG Annual General Meeting

Friday, March 17, 2023
12:30 pm AEST
13:30 pm AEST

More details to follow

Is there a seismic refraction signature for sulphide mineralisation?

Wednesday, October 19, 2022

On Tuesday 19th October, 6:00pm AEDT, ASEG NSW is bringing you a talk by Derecke Palmer (UNSW) titled Is there a seismic refraction signature for sulphide mineralisation?

Although I accepted retirement from UNSW almost two decades ago, I have continued with my longstanding research interests in near surface refraction seismology. The major theme of my research has been full trace processing. Inexorably, full trace processing leads into detailed model building with traveltimes and amplitudes. My presentation addresses three important questions.

The first is “Is there a seismic refraction signature for sulphide mineralisation at the base of the regolith?” The second is: “Will full waveform elastic inversion rapidly replace traveltime acoustic tomographic inversion, and become routine with most geotechnical investigations?” The third is: “Would a detailed analysis of the refraction component of selected regional reflection profiles recorded by GA be useful?” The presentation employs seismic data recorded by GA near a major operational gold mine.

Attendance is by joint Zoom virtual + physical presentation at Geoscience Australia.

Register Here:

Please bring your own drinks and nibbles if attending online.

ASEG NSW - talk by Berta Vilacís

Wednesday, September 21, 2022

Topic: ASEG NSW - talk by Berta Vilacís

Presenter: Berta Vilacís

Date and time: Sep 21, 2022 06:00 PM




Mantle convection is an essential driving force of plate tectonics. It affects the horizontal and vertical motion of the Earth’s surface. The horizontal motion of the lithosphere is observed in the spreading rates, while its vertical motion leaves an imprint the geological record. In particular, positive surface deflections driven by mantle convection create erosional/non-depositional environments, which induce gaps in the stratigraphic record (i.e., hiatus). Modern digital geological maps allow us to map no-/hiatus surfaces at continental scale systematically and use them as a proxy for mantle flow induced dynamic topography. We find that hiatus surfaces change in timescales of geological series. This is consistent with the presence of a weak upper mantle. Also, we find significant differences in the spatial scale of inter-regional hiatus, on the order of 2000-3000 km in diameter, which can be linked by fluid dynamic analysis to active upper mantle flow regions. Our results highlight the importance of geological datasets to further understand geodynamic processes in the deep Earth. Also, they indicate that studies of horizontal and vertical motion of the lithosphere to track past mantle flow would provide powerful constraints for adjoint based geodynamic inverse models of past mantle convection.


Berta Vilacís is a PhD student in geodynamics at the Ludwig-Maximillians-Universität München (LMU Munich). She did her bachelor in Physics in the University of Barcelona focusing in applied seismology during her final year. At the same time she got a one-year fellowship in the Catalonia seismic network. After working in maintaining and processing data from the IEC seismic network in 2017, she moved to Munich where she got her MSc in Geophysics by TUM and LMU Munich. In 2019, she started her PhD in Hans-Peter Bunge’s group. Her research focuses in using geological information, such as geological maps, as a way to observe, map and track past mantle convection.


Presentation “With one arm tied behind your back – Doing geology by proxy in a faraway place (Mars)” by Prof Juergen Schieber

Friday, August 19, 2022

About this event

PESA, GSA SA Division, ASEG and SPE SA Division Science Talk: “With one arm tied behind your back – Doing geology by proxy in a faraway place (Mars)” by Prof. Juergen Schieber (Indiana University).

Friday 19th August 2022 (arrive at 5:15 pm for a 5:30 pm start).

PESA, the GSA SA Division and SPE SA Division would like to invite members and guests to a jointly organised science seminar by Prof. Juergen Schieber (Indiana University), titled “With one arm tied behind your back – Doing geology by proxy in a faraway place (Mars)”.

Location: Mawson Lecture Theatre, The University of Adelaide and online via Zoom.
Date/Time: Friday 19th August 2022. Please arrive at 5:15 pm (5:30 pm to 7: 30 pm).
Cost: $15 per person



Doing geology on other planets, such as Mars, requires for the time being the use of remote controlled rovers. The Curiosity rover on Mars is a rather sophisticated (and expensive) piece of machinery, but geological investigations by rover are labor intensive and slow when compared how we would do comparable tasks on Earth. Although the rover allows us to “see” and “analyze”, critical facets of a geologists traditional “sensory repertoire” are not available (poking around, feel, sound, breaking stuff, smelling and licking). To make up for these deficiencies a large group of highly trained professionals do their level best to analyze the available data and try to arrive at sensible interpretations of what we see. Science by committee, however, has unique risks and “consensus” assessments can still be off-target. Thus, to have more than one well-reasoned interpretation for a single site is not uncommon. Nonetheless, the limitations of this brand of geologic exploration do not hinder progress, and at times they can give us unthought-of new perspectives on things that have become so routine on Earth that we take them for granted (even though we should not). How a limited set of observations can be used to deduce basic modes of sedimentation, diagenesis, and stratal organization in Martian mudstone successions serves as an example on how one could for example do “petrography” without the benefit of a thin section and still make substantial progress. In rover geology you either push your limits or you suffocate in your comfort zone. There is no try.


Prof. Juergen Schieber (Indiana University)

Prof. Schieber is a professor of geology at Indiana University and a specialist on shales. Published extensively (190 papers, 20 guidebook chapters, 4 books, 354 conference abstracts) he is also an invited lecturer at universities in the US, Canada, Europe, and Asia; at research organizations, industry short courses, and symposia. He is the 2022 Sorby Medalist of IAS and a member of the science team that currently explores the geology of Gale Crater on Mars with NASA’s Curiosity rover.

His research is characterized by a holistic approach to shales, and consists of an integration of field studies (facies, stratigraphy) and lab studies (thin sections, electron microscopy, and geochemistry) in order to understand the various factors that are involved in the formation of shales. A key focus point is the experimental study of shale sedimentology via flume studies and related experimental work. Funding for this research is provided by government agencies (NSF, DOE, NASA), foundations (Petroleum Research Fund), and industry via the Indiana University Shale Research Consortium (ExxonMobil, Anadarko, Marathon, Shell, Chevron, ConocoPhillips, Wintershall, Whiting, Equinor, Petrochina) and separate research agreements (Schlumberger/TerraTek; Pioneer Natural Resources). He consults on matters pertaining to shale sedimentology, shale fabric and pore structure, and also teaches short courses on shale sedimentology and facies analysis, as well as microscope-based petrography.

His research interests include: Basin Analysis and Sedimentology, Sedimentology, Diagenesis, and Pore Systems of Shales, the Genesis of Black Shales and Sediment hosted Mineral Deposits, Evolution of the Belt Basin and the Devonian basins of the eastern US, Geochemistry of Sediments, Planetary Geology and sedimentary geology of Mars.

When: Friday 19th August 2022. Please arrive at 5:15 pm (5:30 pm to 7: 30 pm).

Where: Mawson Lecture Theatre, The University of Adelaide and online via Zoom.

Zoom link: Details will be emailed to members prior to the meeting.

Cost: $15 per person

Please join us afterward in the Sprigg Room (top level of the Mawson Building, The University of Adelaide) for further discussions, drinks and nibbles (until 7:30 pm).

Please note that this event will be COVID-19 dependant. All COVID-19 precautionary measures will be in place, with all government restrictions adhered to. Please see the South Australian Government COVID-19 website for the most up to date information.


Monday, September 4, 2023

The 8th International Workshop on Airborne Electromagnetics will be held at Fitzroy Island, Queensland Australia, in person between the 4th and 8th September 2023. Fitzroy Island is an unspoilt tropical paradise of rainforest and beaches within the calm sheltered waters of the Great Barrier Reef. The island is a National Park, with walking trails, tropical plants and animals, and abundant marine life.

The Workshop will encompass advances in airborne electromagnetic systems, modelling and interpretation. Case studies covering geotechnical, mining, energy, groundwater and environmental applications will be presented. The event will be a platform to contribute, discuss and learn about airborne electromagnetics and provide a forum for in-depth conversations on the subject area with colleagues from Australia and worldwide.

A four-day program will feature speakers from academia, government and industry, with keynotes delivered by leading experts in their respective streams.

We look forward to welcoming you to the 8th International Airborne Electromagnetics Workshop.


Key Dates

Call for Extended Abstracts Open 12th September 2022
Online Registration Open End of February 2023
Call for Extended Abstracts Close 1st February 2023
Notification of Abstracts May 2023
Deadline to accept abstract May 2023
Early Bird Registration Close 9 June 2023


Keep updated with the latest news on AEM 2023 by subscribing.


NExUS - Geological Interpretation of Aeromagnetic Data – a Practical Approach

Tuesday, August 2, 2022

Geological Interpretation of Aeromagnetic Data – a Practical Approach

2-Day Online Workshop, 1st – 2nd August 2022

(Limited to 30 places)


NExUS-Professional Development (NExUS-PD) is proud to be able to present this very highly regarded workshop online for the very first time.
• The specially designed two-day online workshop* will introduce the fundamentals of geological interpretation of aeromagnetic data.
• The workshop will feature lectures, practical activities and case studies all using integrated data sets.
• Each day will feature 3 x 2hr sessions with exercises to be completed between the sessions and time allocated for extended discussions.
• The format aims for open, transparent communication, with input from participants highly encouraged to share knowledge and experiences.
*This is a level-4 course (honours level) and is designed to be suitable for early career geoscientists, honours students and HDR students. The workshop is not assessed.


Day 1, Methodology of Aeromagnetic Interpretation – David Isles (1st Aug) :
• Sessions will include: Basic Principles, Physics and Concepts of Magnetics, Spatial Concepts, Survey Planning, Processing and Presentation of Data, Anomalies, RTP and Analytical Signal, Modelling and Inversion, Introduction to Golden Dyke Prospect Case Study
Day 2, Geological Interpretation and Structure – Leigh Rankin (2nd Aug) :
• Sessions will include: Golden Dyke Prospect Case Study, Magnetisation in Rocks, Charters Towers Case Study, Structures in Magnetics, Widgiemooltha Case Study, Unusual Magnetisation and Final Q+A session.

To Register, click here. 

Full Registration: $500

AIG and ASEG Members: $400

Students: $50

For further information view this flyer or, please contact: