The Department of Geological Sciences and Geological Engineering Visiting Speaker Series Presents:

Dr. Jeffrey Shragge, Colorado School of Mines

Talk Title: Observations from the Seafloor: Low-frequency Ambient Wavefield Seismology on Large Seafloor Nodal Arrays

Date: Tuesday, October 24

Time: 10:30 am - 11:30 am 

Location: BIOL SCI 1102

Coffee and treats will be served.

Abstract:

Estimating accurate Earth models for 3-D seismic imaging and full waveform inversion (FWI) remains challenging due to limited low frequencies (i.e., below 2.0 Hz) typically available from active seismic sources such as air guns or dynamite. Naturally occurring ambient wavefield energy acquired on large continuously recording nodal arrays, though, presents a potential alternative energy source for subsurface investigation. By exploiting principles of seismic interferometry in deep-water marine settings, low-frequency (sub-2.0 Hz) virtual shot gathers can be generated with surface-wave events that exhibit clear sensitivity to large-scale model features including salt bodies. These observations suggest a pathway forward for estimating long-wavelength 3-D elastic models required for accurate FWI and seismic imaging analyses. Finally, the use of ambient seismic wavefield interferometry is not restricted to soft-rock investigations and these methods increasingly are being applied in terrestrial hard-rock mineral exploration due to the significantly lower economic costs of acquiring ambient versus active-source nodal wavefield data.  

Biography:

Jeffrey Shragge is a  Professor in the Geophysics Department at the Colorado School of Mines and is a co-Leader of the Mines Center for Wave Phenomena (CWP) research consortium. Jeffrey received a BSc in Physics from Queen’s University, a MSc in Geophysics from the University of British Columbia, and a PhD in Geophysics from Stanford University. He is a former Editor-in-Chief of the journal Geophysics and the past Vice-President of Publications on the Society of Exploration Geophysicists Board of Directors. Jeffrey’s research interests include seismic imaging and inversion, wave propagation, near-surface geophysics, scientific high-performance computing, archeological geophysics, and humanitarian applications of geophysics.

The Department of Geological Sciences and Geological Engineering Visiting Speaker Series Presents:

Dr. Danielle Fortin, University of Ottawa

Talk Title: Chemical, mineralogical and sorptive characteristics of Biogenic Iron Oxides (BIOS)

Date: Thursday, October 5

Time: 12:30 pm - 1:30 pm 

Location: Miller Hall, Room 201

Coffee and treats will be served.

Abstract: 

Biogenic iron oxides (BIOS) form when Fe(II)-rich anoxic waters encounter sub-oxic conditions which are ideal conditions for neutrophilic iron oxidizing bacteria. The end result of their metabolic activity is the formation of occasionally large accumulations of poorly ordered iron oxides mixed with bacterial exopolysaccharides (in the form of sheaths and stalks). X-ray diffraction analysis indicates that BIOS are mainly composed of poorly ordered ferrihydrite but small amounts of lepidocrocite and goethite are also present. BIOS present in pH-neutral mining-impacted areas have been shown to immobilize large quantities of toxic metals, including Pb and Zn and metalloids, such as As. Microbial reduction experiments have revealed that the sorbed contaminants are however released back into solution, along with Fe(II) when BIOS undergo reductive dissolution. In addition, iron-rich biofilms collected from acid mine and acid rock drainage areas were analyzed for their rare earth element content (REEs content). Results indicate that REE sequestration is strongly pH dependent. Lower pH values are associated with greater aqueous REE concentrations whereas, higher pH values are associated with greater biofilm REE concentrations. The total REE content of dried biofilms was two to five orders of magnitude higher than the REE content of co-existing waters. Ongoing experiments are investigating the organic carbon content of BIOS on metal sorption and the role of sorbed impurities (such as Si and PO4) on their microbial reduction. In summary, natural BIOS play a key role in various contaminants’ fate and have the potential to be used to clean-up contaminated areas as long as oxic conditions are maintained within BIOS in order to prevent reduction and contaminant release.

Bio:

Professor Fortin is known internationally for her work on iron geomicrobiology. She established one of the first geomicrobiology research lab in Canada when she joined the University of Ottawa. Professor Fortin is an elected Fellow of the Geochemical Society and the European Geochemical Association. She is also a frequent panel member of the NASA Exobiology program and the NSF Geobiology program. Professor Fortin has been a pioneer in the field of geomicrobiology, inspiring a new generation of geomicrobiologists worldwide.

This talk has been cancelled

The Department of Geological Sciences and Geological Engineering Visiting Speaker Series Presents:

Dr. Regina SK Lee, York University

Talk Title: Nanosatellite Technologies for Space Situational Awareness (SSA)

Date: Thursday, September 28

Time: 12:30 pm - 1:30 pm 

Location: Miller Hall, Room 201

Coffee and treats will be served.

Abstract: 

Space systems play an important and integral role in every facet of our daily lives, including national security and resource management. Therefore, it is critical to protect our valuable assets in space through space surveillance and build resiliency in space systems. In this presentation, an overview of technology advancement in the space research, in particular, nanosatellite (smaller than 10 kg) missions for space surveillance are discussed. Most significant advancement in nanosatellite technologies came alongside the advances in microsystems technologies. It has been a focus of our research team at York University, to develop a series of nanosatellite technologies that will lead us to an advanced scientific mission in near future. Several technologies are under development including optical phased array design, sun sensor development and star trackers. In particular, our recent effort is on (1) nanosatellite attitude control system and (2) resident space object (RSO) detection and identification using a wide field of view cameras such as star trackers. Two key technologies – digital sun sensor design on IRIS mission (Geology mission on a CubeSat platform) and RSONAR mission onboard Stratos Balloon platform are presented as examples of technology development for space-borne scientific missions.

In developing a digital sun sensor (DSS), significant improvements in the design is enabled by advanced micro-systems fabrication and optical sensing technologies. For the IRIS mission (often described as a marriage between geology and engineering), we developed a simple single-slit DSS concept with improved accuracy using sub-pixel interpolation. In considering the DSS design, we focused on several characteristics of the sun sensor, including field-of-view, sensor accuracy, complexity, and computational requirements. From the simulation study, the optimal mask design was determined based on the simple geometry of the slit size, mask height and pixel width. The final demonstration from the in-orbit operation of IRIS is expected once the communication to the satellite is established. Second payload, RSONAR technology demonstration payload, Resident Space Object Near-space Astrometric Research (RSONAR) is a star tracker-like, wide FOV camera combined with commercial off-the-shelf (COTS) hardware to image RSOs from the stratosphere, overcoming the disadvantages of ground-based observations. This newly developed payload in a 2U-CubeSat form factor was flown as a space-ready payload on the CSA/CNES stratospheric balloon research platform to carry out algorithm and functionality tests in August 2022. Results and lessons learned from the campaign are described in the presentation.

Bio: 

Regina Lee, PhD, PEng is Professor at the Department of Earth and Space Science and Engineering, York University, Toronto, Canada. Prof. Lee received her Ph.D. from the University of Toronto in 2000. From 2000 to 2007 she worked at Dynacon Inc. as a (NSERC) industry post-doctoral fellow, and later as a Research Scientist. Prof. Lee’s research interests center on nanosatellite technology development. It has been a focus of Prof. Lee’s research to develop a series of space technologies that will lead to scientific nanosatellite missions. Currently, she’s investigating several areas including MEMS based attitude sensors and actuators to incorporate their low-grade characteristics; and optical payloads including a star tracker for Resident Space Object (RSO) detection, identification and characterization with light curve analysis. E-mail reginal@yorku.ca.