Biogeophysics: Exploring Earth's Subsurface Biosphere using Geophysical Approaches
Microorganisms are found in almost every conceivable niche of the Earth from hydrothermal vents in the deep ocean basins to the cold subglacial lakes of Antarctic ice sheets. As such, microorganisms have played an important role in transforming Earth’s systems (e.g., accelerating mineral weathering), influencing global climate change, and mediating different biogeochemical cycles over most of Earth’s 4 billion-year long history. In-situ microbial-rock interactions are dynamic and occur at both temporal and spatial scales that prove difficult to investigate at resolutions needed to fully understand them, thus necessitating the need for the development of non-invasive tools and sensors to interrogate these processes. Interestingly, these microbial-rock interactions modulate changes in physical properties in the rocks, generating measureable geophysical signatures that can be recorded with conventional geophysical sensors (e.g., seismic, magnetics, electromagnetics). The recognition of these microbial-catalyzed changes in geophysical signatures has resulted in the development of Biogeophysics—the study of the physical changes in Earth materials catalyzed by microorganisms that are observable with geophysical techniques—as an interdisciplinary field of study. In this presentation, I will provide examples of how geophysical tools are used to sense subsurface microbial activity, from cell growth and biofilm formation to biomineralization, biogeochemical cycling of metals, and the monitoring of microbial-induced natural attenuation of contaminants. I will also highlight challenges and limitations and discuss the potential for future advancements in the field.
Technical Talk: Buried Basement Faults: What Can We Learn About Earthquake Rupture Zones from Electrical and Aeromagnetic Data?
Rupture on subtle, critically-stressed, unmapped basement faults in intraplate settings far away from known plate boundaries often results in devastating earthquakes that are a surprise due to the buried nature of the faults. While post-rupture seismological investigations can highlight the buried fault or damage zone and advance our understanding of the kinematics and rupture process, such studies are unable to mitigate the pre-earthquake seismic hazards because they simply do not know where to look. It is important that critically-stressed basement structures (such as faults and lithologic contacts) are identified in advance for effective earthquake hazard analyses. In this presentation, I will use high-resolution aeromagnetic and electrical resistivity data to investigate deeply-buried seismogenic basement structures at three study sites: the 2009 Mw6.0 Karonga, Malawi; the 2016 Mw5.1 Fairview, Oklahoma; and the 2017 Mw6.5 Botswana earthquake zones. These examples highlight the role of pre-existing structures in strain localization and demonstrates that, while aeromagnetic data is very useful in imaging causative buried faults in the basement, it is currently underutilized for this purpose.
Bio:
Estella A. Atekwana received her B.S. and MS from Howard University, Washington DC and a PhD from Dalhousie University, Halifax, Nova Scotia, Canada. She is currently the Dean of the College of Earth, Ocean, and Environment at the University of Delaware. Before joining the University of Delaware in 2017, she was Regents Professor, Head, and Sun Chair Professor of the Boone Pickens School of Geology at Oklahoma State University. She was previously a Professor at Missouri University of Science and Technology, Indiana University Purdue University, Indianapolis and Western Michigan University.
She has served on several committees within the American Geophysical Union (Honors and Awards, Chair, Africa Award for research excellence in earth and ocean science, College of Fellows Task Force, Budget & Finance, Meetings, and Sullivan Awards Committees, Associate Editor, JGR-Biogeosciences), Environmental and Engineering Geophysical Society (Board of Directors & VP Committees), and Society of Exploration Geophysicists (Committee of Special Merits and Women’s Network Advisory Committee). She is a member of the U.S. National Committee for the International Union of Geological Sciences, National Academies. She has also served as a panelist for several federal agencies including DOE, NSF, NIH, and NRC.
Her research on geophysical studies of geomicrobiology processes pioneered the new sub-discipline of biogeophysics. Atekwana has also published extensively in the tectonics of East Africa Rift System and examines how incipient magma poor rifts form.
She is a member of the American Geophysical Union, Geological Society of America (Fellow), Society of Exploration Geophysicists (SEG), National Association of Black Geoscientists and Geochemical Society. She received SEG’s 2016 Outstanding Educator Award.