& present 2022-2023 Geophysics Seminar Series

Location: In-person (ES2093 or otherwise noted) and/or Zoom Time: Tuesday afternoons (4-5 pm during school year, 4-5 for KEGS Virtual meeting, 3-4 pm during summer, unless otherwise noted) To subscribe/unsubscribe from the UofT Geophysics Seminar Email List, please check out the email list web page. 2023 Summer Schedule (Temporary) Joshua Guerrero (June 6th) Upcoming Talks Past Talks >2022-2023 J. Tuzo Wilson Lecture: Carbon Capture and Sequestration; Panacea or Indulgence? Date/Time:Feb 28 2023, 7:30-9 pm Location: Isabel Bader Theatre, Victoria University Speaker: Prof. Roel Snieder (W.M. Keck Distinguished Chair of Professional Development Education at CSM) Affiliations: Colorado School of Mines Abstract: Current events show that climate change is upon us. The mechanism of global warming was already explained fairly accurately by Arrhenius in 1896. An alternative to reducing greenhouse gas emissions by burning less fossil fuels is to capture CO2 and then store it in the subsurface. This technology relies on our expertise in injecting fluids in the subsurface and to monitor the fluids and their fate in the subsurface. This technology has been presented as "a well-accepted leading mitigation strategy against climate change.” In order to understand to what extent this optimism is warranted one needs to consider the following factors: (1) the amount of CO2 that needs to be captured and sequestered to have a significant impact on climate change, (2) the cost of CO2 capture and sequestration compared with other technologies for avoiding CO2 emissions, (3) the reason why CO2 capture is expensive and energy-intensive, and (4) the extreme accuracy with which CO2 in the subsurface needs to be monitored. As with many complicated problems, the devil is in the details, and we need to understand these details to assess the impact of carbon capture and storage that can be expected. This determines whether this technology is a panacea or an indulgence. Title: Date/Time: Jan 17, 2022, 4-5 pm Location: virtual only (see email for zoom link) Speaker: Dr. Bryan James Affiliations: Electromagnetic Geophysical Imaging Solutions, LLC Abstract: In this webinar, a new method of array processing of semi-airborne multi-source, multi receiver TEM data is introduced using beamforming techniques, inspired by their use in other technical fields, to synthetically form impulsive distributions of TEM fields that improve resolution of subsurface geoelectric structure. This form of array processing, currently formulated for 2D problems, is discussed to highlight the fundamental relationship to field interference beamforming methods. The degree of subsurface electric field compaction and magnetic field profile compaction into impulsive distributions is shown to be substantial and depends on depth. The interferographic processing results are then used in a straightforward subsurface imaging procedure for which results are presented for two modeled structural cases: a buried basin and a buried horst. Results are dependent on a reference model and is addressed in detail for the modeled data. Robustness of the interferographic processing is shown with the addition of random noise to the data. Interferographic results for the structural models are also compared with inversion results. Lastly, a brief resolution exercise shows that interferographic processing is an improvement over regular data forms for defining the minimum horizontal separation visibility for two small targets, a direct resolution estimation analogous to that used in signal processing to determine minimum frequency separation of two signals. The future economic commercialization of the ITEM survey design is viable with a set of sparse ground-based sources and high density acquisition for each source position with drone-based receivers. Physics Colloquium: Earth''s Rock and Roll: Rotational Motion in geodesy and seismology Date/Time: Feb 9th (Thursday), 2023, 3-4 pm Location: MP102 (60 St.George St, Physics Building) Speaker: Prof. Heiner Igel Affiliations: Department of Earth and Environmental Science, Ludwig-Maximilians-University Munich, Germany Abstract: The unwanted noise of ring lasers (whenever seismic wave fields perturb their measurements of Earth’s rotation rate) has led to a new field: rotational seismology. The additional ground motion components (i.e. rotation around three orthogonal axes) had been widely ignored, as they are very difficult to measure. Yet, when combined with collocated standard seismometers (three components of displacement) a wealth of information can be recovered from the wavefield. We will report on these new developments with applications in seismic tomography, earthquake physics, planetary seismology, engineering, and other fields. The bottom of the tetradedral-shaped ROMY ring laser measuring Earth’s rotation and rotational ground motions. The sensor is located in the Geophysical Observatory Fürstenfeldbruck near Munich. (Youtube Video from Science Magazine; further Info) Title: Great earthquake rupture segmentation at the eastern Alaska Aleutian megathrust by subducted seamounts Date/Time: Nov 29, 2022, 4-5 pm Location: ES2093 Speaker: Prof. Mladen Nedimovic Affiliations: Dalhousie University Title: Probing earthquake triggering and source processes through multiscale analyses of induced seismicity Date/Time: Nov 15, 2022, 4-5 pm Location: virtual only (see email for zoom link) Speaker: Prof. Xiaowei Chen Affiliations: Texas A\&M University Abstract: In the past decade, the seismicity rate in Oklahoma experienced rise, peak, and decline as a result of varying industry operations. This large-scale “unintentional” earthquake experiment provided us with rich datasets to further probe earthquake triggering and source processes. In this presentation, I present multi-scale analyses of induced seismicity in Oklahoma by combining several studies, and their implications for better understanding of earthquake processes in different tectonic settings. Spatiotemporal patterns of seismicity at regional scale shows systematic regional variations of hydraulic properties of the Arbuckle Group within different pressure units. Spatiotemporal patterns of seismicity within individual sequences exhibit similar behaviors with natural earthquake swarms in tectonically active regions. Systematic large-scale analyses of stress state show that a majority of reactivated seismogenic faults are optimally oriented. However, detailed analyses of stress state evolutions within representative sequences reveal diverse fault planes distributions within swarm-type sequences, and that fault architecture influences sequence evolutions. Focusing on the well-recorded Guthrie sequence in central Oklahoma, diverse triggering mechanisms are observed. The largest event in this sequence shows considerable rupture complexity using finite slip inversion methods. Comparison with slip inversions for earthquakes in different tectonic regions indicates that the level of complexity is similar to earthquakes in low deformation rate regions, suggesting fault characteristics control rupture patterns. Title: Alaska Earthquakes and Earth Structure in the EarthScope Era (2014-present) Date/Time: Oct 26, 2022, 3-4 pm (Wednesday) Speaker: Prof. Carl Tape Affiliations: University of Alaska, Fairbanks Abstract: The subsurface structure of Alaska contains clues to its formation and evolution over geologic time. Today, tectonic forces of subduction and collision are manifest in earthquake activity across the entire state. The NSF-sponsored EarthScope Seismic Array was fully deployed in 2017, enabling new high-quality geophysical data collection in large, remote regions of the state. I will discuss recent and ongoing studies of earthquakes and seismic imaging in Alaska, with a focus on crustal faulting. I will also convey how 3D seismic wavefield simulations can be used to understand the complexities of the recorded wavefield, as well as to guide improvements to tomographic models of crustal and upper mantle structure. 2022 CSEG Distingished Lecture: Geophysics..the future is so bright, we have to wear shades Date/Time: Oct 20th 2022 (Thursday), 4-5 pm Speaker: Dr. Rachel Newrick Abstract: The world is facing many global challenges: poverty, insufficient clean water supply, hunger and a lack of energy security amongst others. To tackle them, the world needs critical thinkers, who are curious and inventive. Utilizing a variety of skills and technologies, geophysicists play a significant role in helping the world meet the 2030 UN sustainable development goals. Geophysicists interrogate the subsurface to locate oil, gas, minerals, water, brine, subsurface reservoirs for carbon sequestration, and to improve our understanding of hazards, earthquakes etc. The thought process that we use in exploration can be used as we look forward to the future, progressing oddities to leads and prospects. The future is bright for geophysicists, and for the world because geophysicists are helping address many global challenges.