Geophysical Research at Memorial University: Building on Our Legacy and Seeking Out New Horizons
Geophysical Research at Memorial University: Building on Our Legacy and Seeking Out New Horizons
J. KIM WELFORD, ALISON E. MALCOLM, COLIN G. FARQUHARSON, AND ALISON LEITCH
MEMORIAL UNIVERSITY, DEPARTMENT OF EARTH SCIENCES, ST. JOHN’S, NL, CANADA KWELFORD@MUN.CA.
Memorial University of Newfoundland and Labrador offers a comprehensive education in geophysics and the broadest range of academic geophysical research opportunities for both undergraduate and graduate students in Atlantic Canada. This article provides an overview of where we are and where we’re going, highlighting opportunities to expand into new avenues of research relevant to the province, to Canadians, and to the world.
Canada is fortunate to host the energy resources that we’ve come to depend on to power our lives, as well as the mineral resources that will be needed to green our economy and the carbon storage sites required to help tackle climate change. The province of Newfoundland and Labrador (NL), in particular, has the potential to satisfy all of these needs, both onshore and offshore. In addition, NL has a long legacy of onshore mapping and offshore exploration, which have generated the data necessary to evaluate the potential to employ these resources to support a sustainable future for Canada. At the same time, the province is no stranger to the destructive consequences of climate change. We have a collective responsibility to mitigate and minimize the harm associated with resource extraction and use, and to monitor those impacts on vulnerable communities. Geophysics has an important role in addressing all of these opportunities and challenges. The Geophysics Group at the Memorial University of Newfoundland and Labrador (MUN) is setting out to systematically address them, as part of our work in training a segment of Canada’s next generation of geophysicists.
The Geophysics Group at Memorial University currently comprises more than 40 people, including faculty (see Table), Research Associates, Post-Doctoral Fellows, and graduate and undergraduate students. Our research expertise spans the full gamut, including field, laboratory, global, mathematical, and computational techniques, with diverse application scales from the near-surface to basins to lithospheric tectonics.
We offer a professionally accredited undergraduate program, which provides two years of geology and basic science courses, after which students interested in geophysics are able to avail themselves of 9 senior level courses in geophysics. Topics include natural resource exploration, environmental and geotechnical geophysics, seismology, potential field geophysics, electrical and electromagnetic geophysics, digital signals in geophysics, mathematical methods in geophysics, tectonics, and geophysics field-school. In our courses, we strive to provide students with a solid knowledge of concepts and methodology, experience with field acquisition, hands-on problem-solving exercises, and coding skills. Student numbers have declined for most Earth science departments in Canada and internationally over the past decade for a myriad of reasons (e.g., pandemic, industry downturn). Still, with new opportunities on the horizon and increasing awareness of the vital role that geosciences will play in society going forward, we are starting to see a rebound in numbers, particularly in the earlier undergraduate years.
Our graduate programs in geophysics remain strong and continue to attract a broad range of both MSc and PhD students from within the province of Newfoundland and Labrador, from across Canada, and from around the world. We currently have 4 MSc students and 9 PhD students enrolled in geophysics programs. In addition, the Geophysics Group at Memorial University is continuing to attract a healthy host of international visitors, including visiting faculty and visiting PhD students from China (funded by the China Scholarship Council and their home institutions), and international MSc students from Turkey (funded by their home governments).
Both our undergraduate and graduate students have access to high-performance computers and state-of-the-art software; a diverse range of geophysical field equipment; and laboratory facilities that can be used to assess rock physical properties and how they respond to geophysical stimuli.
Research collaborations with industry partners provide important funding sources to support graduate students, as well as opportunities for professional internships for both undergraduate and graduate students. Specifically, at present, TGS Canada Corporation (TGS), Petroleum Geo-Services (PGS), the Oil and Gas Corporation of Newfoundland and Labrador (OilCo), Cenovus Energy Inc., Chevron Canada, and Total are providing invaluable support that is generously matched by both federal (Natural Sciences and Engineering Research Council of Canada, NSERC) and provincial (Mitacs) funding agencies. A consortium research project on electromagnetic (EM) geophysics involving a combination of mining companies and service providers is also in the process of coming together.
Past Geophysical Research at Memorial University
The Geophysics Group at Memorial University has an established history of geophysical research, with a recent overview on East Coast Margin research having appeared in an earlier issue of the Recorder (Welford et al., 2019). That contribution focused on 1) assessing the Precambrian and Appalachian building blocks of the province, both onshore and offshore, in large part involving the LITHOPROBE project (Hall et al., 1998, 2002); 2) understanding the structure and evolution of the continental shelf and margins (Lau et al., 2006; Deemer et al., 2009, 2010; Welford et al., 2010a, 2010b, 2012, 2018; Welford and Hall, 2007, 2013; Peace et al., 2018, 2019); 3) characterizing offshore basins and their resources (Gouiza et al., 2015, 2017; Sandoval et al., 2019); 4) quantifying uncertainty in 4D seismic imaging (Ely et al. 2018; Kotsi et al., 2018; Willemsen and Malcolm, 2017); and 5) controlled-source electromagnetic investigations of offshore basins (Nalepa et al., 2016; Squires, 2016; Dunham et al., 2018).
Follow-up studies are continuing on all of these topics, including ongoing East Coast research involving deformable plate tectonic reconstructions (King et al., 2022a, 2022b; Peace et al., 2022), crustal-scale seismic and potential field studies (Welford et al., 2020a, 2020b), and semi-supervised machine learning for well log and seismic facies classification (Dunham et al., 2020a, 2020b, 2021). Further studies of uncertainty quantification (Kotsi et al., 2020, Kumar et al., 2021) and other seismic imaging technique development (Jaimes-Osorio et al., 2020, 2021) are also ongoing. In addition, there remains a continuing focus on the development of new methodology and software for computer modelling of gravity, magnetic, DC resistivity and EM data, with an emphasis on being able to deal with the complexity of real-life geology and the size of modern datasets (e.g., Long and Farquharson, 2019; Darijani et al., 2020, 2021; Carter-McAuslan and Farquharson, 2021; Lu et al., 2021; Galley et al., 2021).
The group hosts a state-of-the-art acoustics lab facility that works to improve our understanding of the physics of wave interactions with materials and each other (Hayes et al., 2018), as well as the physics of common seismic techniques like Amplitude Variation with Offset (AVO) (Moravej and Malcolm, 2022). This facility has also worked with several companies around the world to assess the properties of rock samples for seismic for mining applications.
The Geophysics Group’s pool of field instruments allows shallow Earth geophysical investigations with a number of important environmental applications. Electrical and magnetic surveys have revealed sites of ongoing serpentinization and carbon sequestration in the ultramafic rocks of the Bay of Islands Ophiolite in western Newfoundland (Lynch, 2016; Abbott et al., 2023). Electrical and electromagnetic methods have been used to locate leakage sites in an abandoned tailing dam and trace the concentrations of spillage in the neighbouring wetland (Blagdon, 2021). Ground penetrating radar (GPR) and sediment coring have been utilized to map the thickness of bogs and the structure of pond sediments, allowing an assessment of carbon content in these environments (Chen, 2018). The structure of present and past landfills has been investigated with a variety of methods (Greene, 2021).
Current Geophysical Research
The remainder of this article focuses on promising research avenues that the current faculty in geophysics are pursuing.
Improved characterization of our offshore margins
Through a partnership with offshore industry experts (OilCo, PGS, and TGS) and support from NSERC, student researchers in the Geophysics Group are currently developing and building a Continuously Evolving Newfoundland Offshore Model (CENOM) that is multi-scale, comprises all of the sedimentary basins and underlying crustal characteristics, is constrained by all available geophysical datasets (e.g., seismic, potential field, well logs), and can be reconstructed back through geological time (Figure 1). A significant component of this project is the development of techniques to allow the building of such a regional 3D model, or “3D map”, of the subsurface. These techniques are enabling the construction of the model in several ways. First, we are using machine learning to establish the structural framework across the margin and to populate the model with physical properties from well information and published geophysical models, all while ensuring that the CENOM model is consistent with current geophysical observations. Second, we are improving upon traditional kinematic plate modelling methodologies by explicitly tying the outcomes of the plate models to current geophysical data. Third, we are not only generating a single model, but also a suite of models in agreement with the geophysical data to address the challenge of non-uniqueness and quantify our model uncertainties.
The CENOM computer Earth model, or “digital twin”, can be visualized interactively and continuously improved as new datasets become available and new analysis techniques are developed within the project. In addition to facilitating traditional frontier exploration pursuits for energy resources, the resulting offshore model will help us identify regions with enhanced potential for carbon storage (see following project) and for critical minerals (ocean-continent transition zones), and to look back through geological time using computer reconstructions and simulations, to explore the fundamentals of how continents break apart and ocean basins form.
Figure 1 – Building the Continuously Evolving Newfoundland Offshore Model from all available datasets and published models. The model will ultimately be used for deformable kinematic plate modelling and model parameter uncertainty quantification (not shown).
Carbon Sequestration and Storage
Offshore Newfoundland and Labrador has seen an unprecedented acquisition of both 2D and 3D seismic reflection data collected by PGS and TGS over the last two decades. In addition to informing the broader framework of the CENOM project described above, these data also offer a unique opportunity to investigate potential CO2 storage locations, which will be key for addressing climate change in the decades to come. Before injecting CO2 into the subsurface, many interrelated questions need to be answered about the potential injection location, including what structures are present to hold the CO2 in place, how big those target reservoirs are, and which regions should be avoided due to seepage risk along faults or from permeable stratigraphic layers. Locations of fluid escape features are also being extracted and mapped to inform risk mitigation. Such approaches will ultimately expedite the analysis of the massive existing seismic catalogue while providing a user-independent and data-consistent structural framework to properly locate, characterize, and categorize potential CO2 storage potential in the offshore.
Looking into the future, once CO2 storage is undertaken, it will be necessary to remotely monitor the injection process to ensure efficiency and reliable containment. We are working on a suite of monitoring methods applicable to offshore NL. These methods will include using machine learning techniques to quantify the uncertainty in models recovered with full-waveform inversion, joint inversion of multiple datasets, and developing test models that mimic structures pertinent to offshore injection in NL (Figure 2).
Through collaboration with colleagues in engineering, as well as with our own lab facilities, we are working to understand how CO2 changes the physical properties of target rock formations. This will help us predict and model how surface seismic data will likely change as a result of CO2 injection, helping to characterize the potential of time-lapse seismic monitoring of offshore sequestration efforts in the future.
As a natural offshoot of these studies, we are also naturally learning about the tectonic evolution of all of the offshore basins captured in the seismic datasets, about novel methods for automatically tracking and identifying faults and fluid escape features in seismic data, and about ground-truth methods for tracking how changes in subsurface properties can be successfully monitored from the surface.
Figure 2 –Surface wavefields interrogating the monitor subsurface to detect leakage following CO2 emplacement.
Lithospheric characterization for onshore mineral exploration
The province of Newfoundland and Labrador is experiencing an ongoing mining boom, with those efforts likely to ramp up as the need for minerals necessary for the greening of the economy becomes more urgent. While most onshore exploration efforts currently involve geological field mapping and aeromagnetic surveying, there is a significant knowledge gap in terms of understanding the deeper lithospheric structural controls on shallow mineralization. Such understanding has been crucial to the mining industry in Australia, and the Geophysics Group at Memorial is endeavouring to achieve comparable understanding for the province through the deployment of an extensive geophysical array across the island of Newfoundland. While still in the planning stages, this research project will ultimately provide the deep lithospheric and full crustal context for understanding mineral formation and emplacement in the central portion of the province, which contains the remnants of the Iapetus Ocean and accreted Gondwanan terranes from the assembly of the supercontinent Pangea.
The array will combine complementary geophysical methods (e.g., magnetotellurics, passive seismology, gravity), along with existing controlled-source seismic datasets and aeromagnetic surveys, to collectively build a large-scale 3-D structural and physical property (e.g., conductivity, velocity, density) model of the prospective regions of the province (Figure 3). The magnetotelluric (MT) survey across central Newfoundland will “see” deep into the lithosphere, just like the “Fingers of God” model under the Olympic Dam mine in Australia obtained by Heinson et al. (2018), which revealed a zone of elevated electrical conductivity deep in the crust, thought to be a possible source of metalliferous fluids, and potential pathways from this source region up to the surface. To obtain comparable lithospheric images below the island of Newfoundland, a multi-part MT survey will be deployed with both widely distributed sounding locations and a densely acquired corridor, roughly following the line of the Trans-Canada Highway for ease of access. The broader distribution of temporary MT instruments will be co-deployed and co-located with a network of fifteen broadband seismograph stations across central Newfoundland to be deployed for a duration of three years. Broadband seismic stations can be used to record small local seismic events while also being sensitive enough to record larger distant earthquakes from all over the world. Energy from the local shallow events can be used to locate active faults and identify regions of increased seismic activity and seismic hazard. Meanwhile, seismic energy propagating from more distant large earthquakes illuminates the crust and upper mantle beneath the network of seismographs, providing information about regional structural variations that are tectonically significant (e.g., the base of the lithosphere, upper mantle anisotropy, full crustal velocity variations) and that can have implications on the emplacement and character of overlying shallow resources.
Figure 3 – Proposed geophysical array with co-located passive seismic and MT stations shown by stars, and the dense MT profile shown as the thick white line. Red stars indicate the locations of permanent broadband seismic stations maintained by the Geological Survey of Canada. The geophysical deployment will ultimately provide conductivity and velocity structure of the lithosphere down to 200 km depth.
Building a world-class hub for electromagnetic research
Building on a track record of electromagnetic research in the Geophysics Group at Memorial University, a new industry-sponsored consortium is being established to enable substantial advancements in computer modelling, inversion methodology, and software development for geophysical EM data, with an emphasis on dealing with the complexities and challenges of real-life mineral exploration scenarios. The resulting technology (methodology and software) and associated knowledge will readily be shared with industry partners.
Specific research targets for the consortium will include doctoral projects about: 1) forward modelling for high contrasts in subsurface conductivity; 2) EM-based induced polarization (IP) forward modelling and inversion; and 3) surface geometry inversion (SGI) for MT data (Figure 4). The use of unstructured meshes and wireframe interfaces in the inversion work represents a particular innovative strength of the modelling approaches undertaken at Memorial. MSc students will also be trained as part of this project, with their work focused on case history-style projects, applying the methods and software developed by the PhD students. An important aspect of the project will be the fostering of a mineral exploration EM community, within Canada and abroad, with the computer modelling technology being used to create educational resources that will help in the understanding of how geophysical EM methods work, such as “fly-through” videos of the electric field, current flow, and magnetic field in a range of 3D Earth models.
Figure 4 – Current best model (solid colours) and new candidate model being tested (ghostly colours) of a graphitic fault zone in the metamorphosed basement from a “surface geometry inversion” of a time-domain EM survey from the Athabasca Basin. This inversion approach parameterizes the Earth model directly in terms of the geological units, and uses global optimization to find the locations of the geological interfaces that give the best fit to the geophysical survey data.
Laboratory Geophysics at MUN
In addition to our work on understanding how to use physical laws to see inside the subsurface, we also work at the lab scale to understand what physical laws apply to new problems. We have a state-of-the-art lab, including laser data acquisition and a variety of different source and receiver setups. We use these to study the physical mechanisms underlying phenomena like AVO (Moravej and Malcolm, 2022) and nonlinear wave interactions. Nonlinear wave interactions occur when two waves interact with one another (Figure 5). The strength of that interaction is strongly dependent on the fine-scale structures present in the rock. Our key goal is to understand what controls these interactions and how they can be used to better understand subsurface changes, particularly changes in subsurface cracks during CO2 sequestration or oil and gas production. Having developed an experimental procedure (Gallot et al., 2015) and studied various aspects of wave interactions within cracked materials (TenCate et al., 2016, Malcolm et al., 2023), as well as exploring both numerical (Rusmanugroho et al., 2020) and theoretical modelling (Melnikov et al., 2022), we are now taking this research in new and exciting directions.
The first direction involves using machine learning to try to learn the physics that controls the wave-wave interactions. This involves using and developing techniques that test various potential theoretical models and learning which models fit the data best. These are brand-new techniques that we hope will allow us to understand what signatures cracks put on these wave interactions and how we can use those signatures to remotely infer crack properties. In the second direction, we will work with colleagues in engineering and cutting-edge technology designed for the analysis of micro-electronics to image the interior of our samples during these wave-wave interactions. This kind of direct observation of these interactions will help us to better exploit these unique phenomena to learn about Earth’s structures and processes.
Figure 5 – (Left) Picture of a standard lab setup; (right) illustration of the interaction of two waves within a rock sample.
Environmental field geophysics for addressing coastal erosion
In terms of our environmental field geophysics endeavours, a present focus is on using geophysical methods to study the subsurface structure of regions subject to coastal erosion (Kilfoil et al., 2018; Arshian, 2023). The rugged coastline of Newfoundland and Labrador hosts many communities which may be vulnerable to rising sea levels, intensified storms, and changing precipitation associated with climate change. Ground penetrating radar (GPR) and resistivity surveys can reveal ground structure in vulnerable areas, aiding the design of mitigation strategies (Figure 6). With the recent destruction experienced in southwestern Newfoundland during post-tropical storm Fiona in September 2022, the need for such studies is becoming increasingly urgent.
Figure 6 – A) GPR profile revealing ground structure under a vulnerable section of a coastal road, Bay Bulls, Newfoundland (Arshian, 2023). B) DC resistivity inversion result for unstable cliff region in western Newfoundland, revealing the depth of interface between resistive overburden and weak clay (Kilfoil et al., 2018).
New opportunities for exciting geophysical research are shaping up at Memorial University, building on decades of geophysical achievements. We are eager to embark on these new paths of discovery and welcome collaborations with industry and other academic and governmental parties.
We graciously thank the following groups for financial support for our students and research: the Hibernia Project Geophysics Support Fund (provided by Hibernia Management and Development Company Ltd.), Cenovus Energy Inc., Chevron Canada, Oil & Gas Corporation of Newfoundland and Labrador, TGS Canada Corporation, Petroleum Geo-Services (PGS), Total, NSERC, Mitacs, and others. Figure 2 for this article was prepared by Abolfazl Khan Mohammadi.
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