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National

Webinar: Exploring for minerals, not anomalies: Developing quantitative interpretations of MT models. Dr Kate Selway, Macquarie University

Thursday, February 25, 2021
1300 AEDT
1400 AEDT

1pm AEDT February 16th,

Dr Kate Selway, Macquarie University.

Title: Exploring for minerals, not anomalies: Developing quantitative interpretations of MT models.

Abstract: Exploration geophysicists are well acquainted with making quantitative interpretations of near-surface geophysical data. There is a good understanding of how shallow anomalies in potential field, resistivity or EM datasets relate to mineralisation. However, as exploration models begin to include the lower crust and the lithospheric mantle, there remain significant gaps in our interpretation of deeper geophysical data. In this talk, I will highlight some new advances in our ability to produce quantitative interpretations of these deeper geophysical data, with a particular focus on MT and its joint interpretation with seismics. I will show the newly released software 'MATE', which allows MT models to be interpreted in terms of temperature and composition, and discuss new results from the Eastern Goldfields Superterrane of the Yilgarn Craton, which show how quantitatively interpreted MT models can feed into improved exploration strategies.

Bio: Dr Kate Selway is a geophysicist and researcher who specialises in the MT method and improving interpretations of mantle geophysics. She recently completed an ARC Future Fellowship based at Macquarie University and has previously held research positions at the University of Oslo, Lamont-Doherty Earth Observatory, Yale University and the University of Adelaide, after completing her PhD at the University of Adelaide in 2007. Her research has spanned giant mineral deposits in Australia, active rifting in East Africa, and mantle uplift in Greenland and Antarctica.

https://us02web.zoom.us/webinar/register/WN_OPdMzdnaQbapkiVh7a4ViQ

Webinar - Seismic imaging of the crust using Bayesian joint Inversion of teleseismic P-wave coda autocorrelation waveforms.

Tuesday, February 2, 2021
1230 AWST
1330 AWST

On Tuesday 2 February, 3:30pm AEDT FedEx is bringing you a talk by Dr Mehdi Tork Qashqai from the CSIRO on Seismic imaging of the crust using Bayesian joint Inversion of teleseismic P-wave coda autocorrelation waveforms.

Deep crustal-scale structures are critical for controlling and development of a wide range of mineral deposits. Incoming seismic waves generated from teleseismic earthquakes can be used to image the deep crustal structures. Traveltimes of the teleseismic P and mode-converted S-waves and their reverberations place a tight constraint on the Vp/Vs ratio, and their amplitude ratio provides tight bounds on the P and S wave velocity jumps across the main discontinuities/boundaries in the subsurface structure below a seismic receiver. Teleseismic P-to-S converted waveforms have been used for decades to estimate the shear-wave velocity of the subsurface and depths of major discontinuities below a seismic receiver through a method known as the P receiver functions. In this presentation, a new and alternative approach is presented. Waveforms associated with the P and all mode-converted shear waves are extracted by the autocorrelation of the teleseismic P-wave coda recorded on the radial and vertical component of a three-component receiver. Then, these waveforms are jointly inverted using a probabilistic joint inversion framework to simultaneously estimate seismic properties of the crust (Vp, Vs and Vp/Vs). This approach is particularly useful when there are no high-quality and reliable receiver function waveforms. This approach is cost-effective and can be used in conjunction with the inversion of receiver function, or the deep active seismic reflection profiling to obtain additional/complementary information on the subsurface structure, especially at middle and lower crustal depths where the deep seismic reflection method has penetration problem. In this presentation, I will show some synthetic and real data examples to confirm the feasibility of this imaging technique and also to encourage further application of this approach.

 

Bio:

In November 2012, Mehdi joined the PhD program at Geodynamic and Geophysics group at Macquarie university in Sydney, Australia. His research focused on the development and implementation of a multi-parameter geophysical inverse modelling tool known as “LitMod”. In August 2016, Mehdi completed his PhD thesis entitled “Multi-observable Probabilistic Inversion for the Thermochemical Structure of the Lithosphere". Prior to his doctoral study, he was working in the oil and gas exploration industry for 6 years as a seismic processing and team leader geophysicist, delivering processing, imaging, and quantitative interpretation of seismic data. He joined the CSIRO Deep Earth Imaging Future Science Platform (DEI FSP) in July 2017 as a postdoctoral fellow. He is currently a research scientist at CSIRO DEI FSP and his main research in the “Geoscience Imaging” pillar of the DEI research is focused on the developing and application of new passive seismic imaging approaches to obtain better tomographic models of subsurface structure across multiple scales (e.g., from exploration-scale to lithospheric-scale). 

 

Register now: https://us02web.zoom.us/webinar/register/WN_JKe1Im6oSTmmBSh9h7EnSg

GA’s new geophysical archive and data delivery system: GADDS 2.0

Wednesday, December 9, 2020
1530 AEDT
1630 AEDT

On Tuesday 9 December, 3:30pm AEDT the ACT branch is bringing us a talk by Simon van der Wielen on GA’s new geophysical archive and data delivery system: GADDS 2.0

Geoscience Australia’s Geophysical Archive Data Delivery System (GADDS) brings magnetic, radiometric, gravity and digital elevation data from Australian National, State and Territory Government geophysical data archives together into a single location.

As the current platform on which GADDS resides is reaching the end of its life, Geoscience Australia has been preparing to migrate to a new platform. Following a period of testing, the system will be officially released in December 2020. The new platform offers users a simpler and faster experience with greater flexibility over form and size of data delivery. Over time, the platform will also offer access to a broader range of data including multi-variable datasets such as airborne EM and airborne gravity and gradiometry.

The migration of this platform primarily supports Geoscience Australia’s enabling an informed Australia priority area.

Register now: https://us02web.zoom.us/webinar/register/WN_7sEBLy1ATmmtZq1ZtcN99A

NSW student night presentations

Wednesday, November 18, 2020
1800
1900
Wednesday, 18th November, 6-7pm
 
NSW student night, presenters: 
 

- Tom Zhao (UNSW) – NSW student scholarship winner

- Kelly Vaughan-Taylor (Macquarie Uni)

- Sue Chan (Uni of Sydney) 

 
More details to follow!   
 
To register, please use the following link: https://us02web.zoom.us/webinar/register/WN_3M3CXGfHTkmU3cNEru1qUw

ASEG WA Webinar: Pre-stack Depth Imaging: Challenges in exploration-scale volcanic geobody model-building in the Potiguar Basin, Brazil

Tuesday, November 10, 2020
1500 (AWST)
1600 (AWST)

Pre-stack Depth Imaging: Challenges in exploration-scale volcanic geobody model-building in the Potiguar Basin, Brazil

Rich Bartlett, Shearwater GeoServices

Register here: https://us02web.zoom.us/webinar/register/WN_PRBuo4cySDixmFf5QwTLMQ

The Potiguar Basin includes the largest oil-producing region in Equatorial Brazil, where production is from the syn-rift to transitional successions. The Pitu well in the deep-water offshore part of the basin found oil, gas and condensate at depths of 4,300m in Upper Aptian sands of the Alagamar and Pescada Formations.

 

A 10,500 km² 3D survey was acquired in 2019 and seismic processing through PSDM imaging was initiated. The presence of high velocity volcanics in the sedimentary sequence presents unique imaging challenges for Pre-Stack Depth Migration (PSDM). By their nature, volcanic geobodies have a varying thickness, velocity fill and extent, and require detailed interpretation to be represented accurately in a PSDM anisotropic model. This talk will present an iterative and efficient methodology to interpret and refine volcanic geobodies with examples from this exploration-scale PSDM survey.

 

Rich Bartlett, Depth Imaging Manager from Shearwater GeoServices. Rich graduated in 2002 from the University of Leeds UK and Queen's University Canada with a Masters In Geophysics. He spent his early career as a Geophysicist at Veritas DGC with various roles in the Depth Imaging teams in both London and Calgary offices, moving through the various incarnations of CGGVeritas and CGG. This was followed by 3 years consulting with Monarch Geophysical Services on a range of marine and land acquisition and processing projects before moving back to the frontline with Dolphin Geophysical in 2013, and latterly with Shearwater GeoServices. Rich has helped build Shearwater's Depth Imaging capabilities from scratch, with Shearwater now offering a wide range of inversion and imaging services behind its vessels and to the open proprietary market.

 

Professional Development Course - Quieten your Inner Critic Workshop

Wednesday, November 11, 2020
1230 (AEST)
1430 (AEST)

Professional Development Course - Quieten your Inner Critic Workshop

Wednesday 11 November at 12.30-2.30pm AEST (Online)

To register, click here

Same cost as before: free for members, $25 for non-members.

We've explored how to break the cycle of feeling like a 'fake' at work. We've worked with the framework to be aware of that nagging voice in our head telling us that it was 'luck'. And we now know, we're not alone. What next?

With 70% of us experiencing 'impostor' like symptoms in our careers, this informative and inspiring interactive workshop sees us shift from an 'Impostor Life' to managing our 'Impostor Moments'. We'll balance our Inner Critic with our Wiser Self, build our evidence and re-energise our confidence to drive future success.

This workshop comes on the back of the popular course, Overcoming your Inner Critic, held in August. This workshop is a continuation, but if you didn't attend - IT'S OKAY - the facilitator will bring you up to speed. Cost is free for ASEG Members, $25 for non-members. Visit the ASEG Events page for further information, or click on the image below to watch the video...

 

ASEG Webinar - Stranded stream channels investigated by LiDAR mapping, some geophysics and good old leg work. Insights into the Lapstone Structural Complex west of Sydney.

Wednesday, October 21, 2020
1800 (AEST)
1900 (AEST)

Brought to you by NSW on Wednesday 21 October, 6pm (AEST) for a talk by Peter Hatherly.

 

Stranded stream channels investigated by LiDAR mapping, some geophysics and good old leg work. Insights into the Lapstone Structural Complex west of Sydney.

 

In the contemporary parlance, the western boundary of what the media call the Sydney Basin is the Lapstone Structural Complex. The front range of the Blue Mountains. This abrupt escarpment rises to a maximum height of 600 m above the Cumberland Plain and forms an impressive boundary to the Blue Mountains beyond.

Geologists identified the monoclines and faults associated with the LSC as early as the nineteenth century but an understanding of the exact nature of the structure and its timing is still not clear. In this talk I take note of evidence of stranded channels evident in detailed LiDAR mapping, the occurrence of river gravels now high above the Nepean River and seismic refraction results within the Thirlmere Lakes, a curious river system within the southern extension of the LSC.

 

My suggestion is that in its present form, the LSC is probably no older than 10 million years.

 

Register now: https://us02web.zoom.us/webinar/register/WN_klquuUL_Q3a39DbZUM-9rQ

 

The application of 2.5D AEM inversion to resource exploration with reference to open file survey examples from NSW, QLD and WA

Wednesday, September 16, 2020
1630 (AEST)
1730 (AEST)

The application of 2.5D AEM inversion to resource exploration with reference to open file survey examples from NSW, QLD and WA

The application of 2.5D AEM inversion to resource exploration.

The 2.5D AEM inversion technology developed by Intrepid produces spatially accurate images of subsurface conductivity in both cross section and in plan that are mostly free from the problems often seen in CDI and 1D inversions – particularly where 1D assumptions are not met.

Through a series of examples and survey configurations, we will demonstrate that 2.5D inversion products can be used confidently by geologists and geophysicists for orebody targeting and for geological and structural mapping in plan as well as in cross section. These products also facilitate the integrated interpretation of AEM, magnetics, gravity and surface geology.

 

Register now: https://us02web.zoom.us/webinar/register/WN_w83cseQ-RYKQ6K3HoZQamw

 

 

Webinar: Grayscale representative elementary volumes: An innovative approach to investigate pore-scale REVs from raw micro-CT images

Thursday, October 1, 2020
1200 (AWST)
1300 (AWST)

Title and Summary:

Grayscale representative elementary volumes: An innovative approach to investigate pore-scale REVs from raw micro-CT images

Representative Elementary Volumes (REVs) are at the foundation of measuring rock properties that capture local heterogeneities of the rock structure at a particular length-scale for upscaling purposes. High-resolution micro-computed tomography (micro-CT) images of rocks have allowed a full 3D characterization of rock structures at pore-scale. These micro-CT images store information about rock structure as variations in the gray-level intensities or CT numbers. However, the direct use of these information-rich raw micro-CT images for rock characterization has not been possible due to a limited number of rock properties that can be calculated from them. In this study, we implement a novel texture characterization technique called the Gray-level Size Zone Matrix (GLSZM) to analyze the raw micro-CT images. We apply the GLSZM approach to homogeneous and heterogeneous sandstones and carbonates and show that this method highlights important rock features such as mineralogical heterogeneities and sub-resolution porosity. Considering these features, we calculate GLSZM statistics, that serve as proxies to porosity and permeability, which are crucial petrophysical properties. Comparing the trends of these proxies to petrophysical properties at various scales and spatial locations of the rock sample, we then infer Grayscale REVs (GREVs) and validate it using existing literature. Finally, we show that using the GLSZM-based approach, we can infer GREVs in a robust, reproducible, and fast manner. These GREVs can then serve as a priori for further petrophysical characterization of rock samples. 

Bio:

Ankita Singh is a Ph.D. student at the School of Minerals and Energy Resources Engineering at UNSW, Sydney. Her work focusses on implementing texture analysis techniques for rock characterization by directly using raw x-ray images. Her Ph.D. work has been published in reputed journals such as Water Resources Research and Geophysical Research Letters. She also won the 'Best Engineering/Environmental Student Paper' at AEGC 2019 in Perth and was the 2019 Finalist at the UNSW Three Minute Thesis Competition. 

Register now: https://us02web.zoom.us/webinar/register/WN_gYxzak7oQ_y6-AE_JwdXEQ

 

On the cusp of a tear: continental subduction in the Banda arc

Tuesday, August 25, 2020
1430 (AEST)
1530 (AEST)

A new ASEG webinar brought to you by FedEx on Tuesday 25 August, 2:30pm (AEST) for a talk by Meghan Miller.

On the cusp of a tear:  continental subduction in the Banda arc

Eastward along the Sunda-Banda arc, convergence transitions from subduction of oceanic lithosphere to arc-continent collision. This region of eastern Indonesia and Timor-Leste provides an opportunity for unraveling the processes that occur during collision between a continent and a volcanic arc, and can be viewed as the temporal transition of the process of continental collision along strike.  We have collected a range of geological, geodetic, seismic, and geomorphic data to place constraints on the geometry and history of subduction. Utilizing ~4 years of new broadband seismic data we image the structure of the crust through to the mantle. Ambient noise tomography of the crust shows velocity anomalies along strike and across the arc, related to structure of the incoming Australian plate. The pattern of anomalies at depth resemble the system of salients and embayments that are present offshore western Australia, which formed during rifting of east Gondwana. At mantle depths, transition from oceanic subduction to continental collision appears reflected in new teleseismic based images, coinciding with previously identified changes in the geochemistry of the arc volcanics. Results from our body wave tomography show continuity of the subducting slab to depths of at least 300 km, with no evidence for tearing at the scale of >~50 km even in the region of arc-continent collision. Our expanded catalogue of Benioff zone seismicity reveals earthquakes in what was previously thought to be a seismic gap (the Wetar gap). Together, our seismic results suggest that tearing is not as advanced in this region as previously hypothesized, implying sustained subduction of continental lithosphere underneath the Banda arc. We suggest the tectonic evolution of this region is defined by inherited structure of the Gondwana rifted continental margin of the incoming plate.  Altogether, we suggest that this region is characterized by subduction of continental lithosphere poised for tearing that has perhaps just initiated, but with no large slab windows. Therefore, the initial template of plate structure controls orogenesis and deep mantle structure.

Register now: https://us02web.zoom.us/webinar/register/WN_MQI0S4DfQnyKG1hzAzoVYA

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