&
present
2021-2022 Geophysics Seminar Series

 

  Location: Virtual Links in emails

Time: Tuesday afternoons (4-5 pm during school year, 4-5 for KEGS Virtual meeting, 3-4 pm during summer, unless otherwise noted)

Schedule (email liuqy@physics if you have any visitor who would like to give a talk):

10/27: Hilary Martens (U. Montana), Wed 3-4 pm, UTM
11/02: Seogi Kang (Stanford)
11/16: Owens Alile (U. of Benin)
11/23: Shujuan Mao (MIT)
01/25: Don White (GSC)
01/27: Zhongwen Zhan (Caltech, ES seminar Thursday noon)
02/01: Alain Plattner (U. Alabama)
02/22: Kristina Tietze (GFZ Potsdam)
02/23: Catherine Johnson (UBC, Tuzo Wilson Lecture)
03/22: Michael Afanasiev (Mondaic software)
03/29: Hongyu Yu (PGC): Induced earthquakes in western Canada: case studies and new understandings
TBA: Claire Currie (U. Alberta), UTSC CRESS (Fridays 4pm), Camilla Cattania (MIT, UTM Wed 3pm)


Dates reserved for KEGS talks: second Tuesday afternoon of the month
Important Dates: 09/09: fall classes start; 10/11: Thanksgiving; 11/8-12: fall reading week; 12/08: last day of fall classes; 01/10: spring classes start; 02/22-25: spring reading week; 04/08: last day of classes.

Other relevant seminar series at UofT: ES seminar (Thu noon), ES Rockfest (Fri 3pm, run by grads), Physics Colloquium (Thu 4pm), Brewer-Wilson Seminar (Fri noon, run by grads), Center for Global Change Science (CGCS) Seminars (Tue 4 pm), Centre for Research in Earth System Science Seminars (UTSC) (Friday 4pm), UTM CPS Colloquium (Wed 3-4 pm)
For a list of Geoscience events across GTA, check out the GTA Geoscience Events Calendar. Also check out the websites for Toronto Geological Discussion Group (TGDG), Canadian Exploration Geophysical Society (KEGS) and KEGS Foundation.

External webinars of interest: IRIS webinars (Youtube Channel), CIG webinars (Youtube Channel), AGU Webinars, SEG Near surface global lecturers, SEG ON DEMAND (you may need to be an SEG member to view)


Upcoming Talks

2021-22 CSEG Distinguished Lecture: Geological storage of carbon and the role of Geophysics

Date/Time: January 25th 2022, 4-5 pm
Speaker: Don White
Affiliations: Geological Survey of Canada

Location:Zoom Link

Abstract: Global efforts to reduce anthropogenic carbon emissions to the atmosphere are gaining momentum. Geological storage of CO2 is recognized as an important component of most reduction strategies and can contribute to the sequestration of excess CO2 already in the atmosphere. However, to be effective, the quantity of CO2 to be stored must be larger – by several orders of magnitude – than current underground injection of waste fluids or gas storage. This will require new monitoring and storage protocols and geophysical methods will play an important role in all stages of CO2 storage projects including site selection, geological characterization and long-term monitoring. Canada is a world leader in implementing CO2 storage pilot projects and related studies. In 2015, the Aquistore CO2 Storage Project began injection of CO2 into a deep saline formation at ~3300 m depth utilizing the deepest well in Saskatchewan. The total of CO2 injected is approaching 400 kilotonnes. A variety of geophysical methods have been employed to track the subsurface spread of the CO2 plume and verify its containment within the reservoir. Time-lapse seismic imaging has proven effective for tracking the growth of the CO2 plume over the first 5 years. Passive seismic monitoring combined with continuous GPS measurements and InSAR surveillance has documented an absence of induced seismicity or related surface deformation. The site has acted as a natural testbed for developing other geophysical monitoring methods including electromagnetics, borehole gravity, and fibre-optic DAS (distributed acoustic sensing) systems. The knowledge developed at the Aquistore site will benefit future geological storage projects.


Title: Geophysical Sensing on Submarine Cables: A Cocktail for Two Communities

Date/Time: Jan 27th 2022, 2 pm (ES seminar)
Speaker: Prof.Zhongwen Zhan
Affiliations: Caltech

Abstract: The oceans present a major gap in geophysical instrumentation, hindering fundamental research on submarine earthquakes and the Earth’s interior structure, as well as effective earthquake and tsunami warning for offshore events. Emerging fiber-optic sensing technologies that can leverage submarine telecommunication cables present a new opportunity in filling the data gap. Marra et al. (2018) turned a 96 km long submarine cable into a sensitive seismic sensor using ultra-stable laser interferometry of a round-tripped signal. Another technology, Distributed Acoustic Sensing (DAS), interrogates intrinsic Rayleigh backscattering and converts tens of kilometers of dedicated fiber into thousands of seismic strainmeters on the seafloor (e.g., Lindsey et al., 2019; Sladen et al., 2019; Williams et al., 2019; Spica et al., 2020). Zhan et al. (2021) successfully sensed seismic and water waves over a 10,000 km long submarine cable connecting Los Angeles and Valparaiso, by monitoring the polarization of regular optical telecommunication channels. However, these new technologies have substantially different levels of sensitivity, coverage, spatial resolution, and scalability. In this talk, we advocate that strategic combinations of the different sensing techniques (including conventional geophysical networks) are necessary to provide the best coverage of the seafloor and benefit both the geophysics and oceanography communities. Furthermore, strategic collaborations with the telecommunication community without burdening their operation will be critical to the long term success.


Title: The magnetic fields of Mercury and Ganymede

Date/Time: Feb 1st 2022, 4:10-5 pm
Speaker: Prof. Alain Plattner
Affiliations: University of Alabama

Abstract: Of the many planetary bodies in our solar system, including the moons of Jupiter and Saturn, only seven are known to have an active core magnetic field. We will discuss two of these planetary bodies: Mercury and Jupiter's moon Ganymede. Flybys of NASA's Galileo spacecraft two decades ago first detected Ganymede's core magnetic field. Spherical-harmonic analysis of this field led to conclusions that it may be generated in an extremely small fraction of the moon's core. A flyby of NASA's Juno spacecraft last June confirmed this interpretation. In this talk will discuss the limitations of the available data and propose alternative magnetic field models with substantially different interpretations for the magnetic source depth. For Mercury, magnetic data collected by NASA's MESSENGER spacecraft revealed that Mercury's core magnetic field is highly symmetric with respect to Mercury's rotation axis, but not symmetric with respect to the equator. This core field is sometimes described as an offset axial dipole, shifted towards the north pole of the planet by approximately 20% of Mercury's radius. We will discuss a weak non-axisymmetric field hidden beneath Mercury's offset axial dipole. This field spatially aligns with a topographic bulge and a deep-seated gravity anomaly, creating the challenge of how such a connection could be explained geophysically.


rule

Past Talks


Title: Space-Time Monitoring of Groundwater via Seismic Interferometry

Date/Time: Nov. 23rd, 2021, 4-5 pm
Speaker: Dr. Shujuan Mao
Affiliations: MIT

Abstract: Extreme droughts plaguing the western U.S. raise a vital call for sustainable management of fresh water resources. A refined understanding about the structures and dynamics of underground aquifer systems is urgently needed. Here we present a novel approach for monitoring the spatiotemporal fluctuations of groundwater using seismological observations. By combining ambient noise interferometry and coda-wave imaging techniques, we are able to measure the space-time evolution of Relative Changes in Seismic Velocity (Δv/v) in the Coastal Los Angeles Basins during 2000-2020. We find Δv/v to recover the hydraulic head, illustrating the potential of leveraging seismometers to propel the temporal and spatial density of well measurements. Images of Δv/v seasonality agree with surface deformation inferred from InSAR, but also further enable the characterization of aquifers and their hydrology at different depths. Long-term Δv/v suggest that distinct trends (decline and recovery) of groundwater storage occurred in adjacent basins, due to anthropogenic pumping practices compounding the effect of climate change. This pilot application bridges the gap between seismology and hydrology, and shows the promise of using Δv/v to decipher underground hydrologic processes. We anticipate Δv/v to be a unique type of 4D, in-situ geodata, which will add new insights into various dynamic processes in Earth’s shallow subsurface.


Title: Geoelectrical Resistivity Survey for Geoenvironmental Investigation in Benin, Edo South, Nigeria

Date/Time: Nov. 16th, 2021, 4-5 pm
Speaker: Prof. Owens Alile
Affiliations: University of Benin, Department of Physics

Abstract: 3-Dimensional (3D) electrical resistivity survey was carried out by engaging a 2-Dimensional (2D) profile lines in the field, for geoenvironmental investigation at Otofure in Ovia North East LGA of Edo State, Nigeria. A total of fifteen (15) 2D survey lines were acquired in both parallel and orthogonal directions within and around the dumpsites. Both the Wenner alpha and Dipole Dipole arrays were engaged in the survey. Three parallel lines of 60m in length and 3 orthogonal lines of 100m in length forming a rectangular grid format, was adopted at the eastern edge of the site at a distance of 20m away from the dumpsite. Another 6 lines 3 parallel and 3 orthogonal of 100m each forming a square grid format, was conducted at the northern edge of the dumpsite. The length of the 2D traverses varies from 80m to 100m in length and the minimum electrode spacing ranged from 2.5m using the dipole dipole array and 5m interval using the wenner array. The 2D data was inverted using RES2DINV software. The 2D apparent resistivity data were collated into 3D data sets and inversion of the 3D data was done using RES3DINV to give the 3D depth slices. A volume rendering image processing technology Voxler 3D software was used to transform the data into understandable visual 3D block models. The results showed that the subsurface lithology composes of lateritic soil, sands, sandy clay and clay. The results correlated with three Borehole logs of the study area showing various layers. The topsoil, which consists of reddish brown laterite and sandy clay, has resistivity values between 80Ωm and 8500Ωm and its thickness varies between 0.01 m to 7.00 m. The second layer is thick sediments of clay and sandy clay, and has resistivity values between 120Ωm and 4000Ωm. Its thickness ranges between 2.00 m to 16.00 m. The 2D Inversion delineated contaminant plumes have low resistivity zones with resistivity values ranging between 10Ωm and 27Ωm from the ground surface to varying depths of 0 to 7m in profile 7, 8 and profile 9 suspected to be leachate. While profile 1 to 6 which is about 50m from the dumpsite and profile 10 to 15 which is about 100m from the dumpsite delineated contaminant plumes with resistivity zones ranging between 10Ωm to 30Ωm, at varying depths ranging from 7m to 15m below the surface which is suspected to be leachate from decomposed waste. There was no evidence of groundwater contamination as showed by the inversion model in all the profiles.



KEGS November Talk: Deep Learning as an alternative to downward continuation filters for structural interpretation

Date/Time: Nov, 9th 2021, 4-5 pm
Speaker: Jean-Philippe Paiement
Affiliations: Director, Global Consulting, Mira Geoscience

Abstract: Oftentimes when working with regional magnetic surveys from multiple sources, we encounter resolution continuity issues, which makes 2D interpretation more challenging. The loss in resolution of anomalies borders and lack of texture in the gridded data, can cause issues to the interpreter. This talk sets the basis of using currently available deep learning architecture to train a model for special resolution enhancement. Recent advancement in image processing and deep learning have led to the development of neural networks capable of increasing images resolution using and adversarial learning strategy (Wang, X et al., 2018). In this deep learning model, available high-resolution grids with their low-resolution counter parts are used to train an encoder-decoder network to reconstruct the high-resolution from their starting point. Once the network is sufficiently trained it is then possible to apply it to upscale low-resolution images without existing ground truth high resolution counter part. This approach uses Generative Adversarial Networks or GAN’s, a relatively new class of machine learning frameworks designed in 2014 (Goodfellow, I. et al). A generator network is used to construct images that are then passed through a discriminator network which tries to discriminate between real images and fake images produced by the generator. Given a training set, this technique learns to generate higher resolution data with the same statistics as the training set. Once the general model is trained on high-resolution/low-resolution pairs, it is possible to refine it to the area of interest and use it to upscale low resolution survey patches. This will help in refining anomaly edges and increase the accuracy of the structural interpretation conducted by the geologist. This approach is proposed as an alternative to the commonly used downward continuation filters used in the industry.


Title: Advancing Remote Sensing Techniques for Groundwater Science and Management

Date/Time: Nov, 2th 2021, 4-5 pm
Speaker: Seogi Kang
Affiliations: Stanford University

Abstract: Groundwater sustainability is at risk. With the latest mega-droughts, major reservoirs in western U.S.A. expose their bottom. Lack of surface water increases groundwater pumping particularly in highly-irrigated areas such as the Central Valley of California in U.S.A. For sustainable management of groundwater resources, it is necessary to image hydrogeology of the subsurface and monitor spatial and temporal changes of groundwater flow and storage. Traditional well- based approaches provide us useful data for this imaging and monitoring tasks but limited given the poor spatial coverage and density of water wells. The latest enhancement in remote sensing technology provides alternative ways for the imaging and monitoring of groundwater systems. Working with remote sensing data acquired in the Central Valley, in this presentation, I will first present how airborne electromagnetic (AEM) method can be utilized to image large-scale structure of groundwater systems. Then, I will present a potential of using the InSAR (interferometric synthetic aperture) deformation data as a tool for monitoring spatial and temporal changes of groundwater flow.

Bio: Dr. Kang completed his PhD in Geophysics at University of British Columbia, Canada, in 2018. His thesis work focused on computational electromagnetics and its application to mining problems. Currently, he is a Postdoctoral Researcher in the Geophysics Department at Stanford. His research focus is on advancing use of remote sensing methods for groundwater management and groundwater science. He continues to contribute to the development of open-source software, SimPEG, and educational resources, GeoSci.xyz, for geophysics.



UTM CPS Colloquium: Tracking water resources and constraining Earth structure with space geodesy

Date/Time: Oct 27th, 2021, 3-4 pm
Speaker: Prof. Hilary Martens
Affliations: Department of Geosciences, University of Montana

Abstract: see link above.

KEGS October Talk: Yaouré Gold Mine 3D seismic case history and recent hard rock processing and interpretation developments

Date/Time: Oct 12, 2021, 4-5 pm
Speaker: Andy Dyke (speaker), Kevin Jarvis and Greg Turner
Affiliations: HiSeis

Abstract: 3D seismic reflection is gaining acceptance as a tool for accelerating the discovery of additional resources within mineralized environments. In this talk we will show how this is being achieved at the Yaouré Gold Mine in Côte d’Ivoire. In addition, we will show some of the new approaches that are being applied both to: 1. Obtain higher fidelity images which more clearly and accurately represent the subsurface geology; and 2. Derive more intuitive volume-based interpretations showing the 3D distribution of key rock units.





rule