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Staff Profile

Associate Professor Susan Webb

Position ASSOCIATE PROFESSOR
QualificationsBSc, MSc, PhD
Phone 0117176606
Email Susan.Webb@wits.ac.za
Organisational Unit Geophysics

My current research is focused on the application of 3D modelling of the southern African regional gravity field to constrain properties of the K pv l tectosphere. These gravity models are constrained by and integrated with the results from the seismological and geochemical studies of the K pv l project. I am particularly interested in projects integrating diverse data sets, including geophysical, geological, petrologic, isotopic and geochemical information.On a smaller scale I am currently developing a consistent gravity, magnetic and seismological model of the Bushveld Complex that accounts for thickened crust under the Bushveld.I am also interested in the integration of geophysical methods applied to exploration, environmental and archaeological problems with a special focus on potential field methods. This includes high-resolution studies, including the practical aspects of data collection.

Active Major Research Projects

  • The use of potential field and seismological data to analyse the structure of the tectosphere beneath southern Africa. 
  • AfricArray Partnership with Andy Nyblade through Penn State University. The objective is to couple high quality research using broadband seismological stations throughout Africa with a first rate teaching program covering all aspects of Geophysics. Start date: January 2005.
  • Inkaba ye Africa Assisting with coordinating the activities in working group 1: Heart of Africa. This subproject covers diverse aspects such as studies of the Earth?s core, magnetic field interactions, solid Earth tidal responses and mining seismology.
  • DAFSAM/NELSAM (Drilling Active Faults in South African Mines/Natural Earthquake Laboratory in South African Mines) DAFSAM is an ICDP sponsored project to examine the fundamental physics of Earthquakes. I am assisting with coordinating African student projects including wavelet analysis of mine seismology data and detailed geophysical logging of the boreholes.
  • Gravity modelling of the Bushveld Complex ? Flexure of the crust. Jointly with Teresia Nguuri, Dr. David James, Prof. Grant Cawthorn, Prof. Tom Jordan. Seismological results support our earlier proposal that the Bushveld forms a continuous lopolith structure that has resulted in crustal flexure. This has important implications for the origin of the world?s largest layered intrusion, with its vast mineral deposits.
  • Physical Properties of the Bellevue drillcore ? Northern Limb Bushveld Complex. Jointly with Prof. Lew Ashwal, Mike Knoper In order to obtain more measurement of physical properties for geophysical modelling we have measured magnetic susceptibility and density in detail throughout this three kilometre long core. Fascinating cyclicity in the measurements, which was not apparent from the geology, is being analysed using wavelet analysis.
  • Characterization of South African seismicity: April 1997 ? April 1999. Jointly with Profs. Tom Jordan and Cedric Wright Status: Report to funding agency (US DOD) is completed, scientific papers in progress.The purpose of this project is to compile a database of seismic activity in southern Africa from the active mining regions to the few, but important, tectonic events for the period April 1997 to April 1999.
  • Geophysical signature of kimberlite in a magnetically noisy environment: An assessment of geophysical methods applied to the Goedgevonden and surrounding kimberlites. Jointly with Martin Frere (Fugro ? South Africa) The Goedgevonden kimberlite is located close to the highly magnetic Hospital Hill shales and is covered by magnetic scree and resistive, thick ferricrete. The use of airborne EM techniques proved effective in locating this kimberlite and in the discovery of a nearby kimberlite.

Teaching

Geophysics 300: Potential Field Methods 3rd year level, course. This course was developed as background material for the 4th year advanced potential fields course.
Geophysics 400: Advanced Potential Field Methods, 4th year level. This course covers fundamental aspects of potential field theory and their application to the study of gravity and magnetic fields. The course also covers the practical aspects of designing surveys, collecting, reducing and interpreting data. There are several hands-on sessions with department-owned instruments and the interpretation of real data. This course features an introduction to the Unix computing environment, often the only exposure the students have to this system.
Geology 200: Introduction to Geophysics for Geologists. This course is a mostly nonmathematical introduction to geophysical results and methods for geology students. It covers aspects of seismology, gravity, magnetics, heat flow and plate tectonics.
Geophysics for Geologists 400: An introduction to various geophysical methods used in exploration.
Practical Geophysics: The location and nature of this field based course varies from year to year. However, students always conduct a survey involving several geophysical methods. This includes forward modeling in the classroom, site selection, survey design, estimated costs and final written integrated interpretation of the results. Recent trips have focused on: locating water in the Klein Karoo; SAGA Roodekr l national geophysical test site (a copper prospect); extensions of banded iron formation at the Blue Dot Gold Mine (Amalia greenstone belt); Dimension stone, Vredefort Impact Structure (Marlin Granite); Dykes, eastern Bushveld Complex (Modikwa platinum mine)

Administration Portfolio 

Earth Science Committee;  Promotions (Open Day, Schools promotions, Departmental Tours, Radio interviews, TV programs, Anglo video)
Equipment coordinator. Maintenance of equipment
Advertising to other Universities, responding to student enquiries.

Community Service 

  • The South African Geophysical Association (SAGA) is the professional organisation for Geophysicists in southern Africa. We have strong links to the SEG (Society of Exploration Geophysicists) in the USA and the EAGE (European Association of Geoscientists and Engineers). I have been active in SAGA since 1995.
  • 1998 SAGA President
  • Reviewer for South African Journal of Geology, Journal of African Earth Sciences.
  • Commission on Solid Earth Composition and Evolution (SECE) member (2005)

Additional Appointments

  • Researcher MIT 1997 - 2000 
  • Predoctoral Fellow Carnegie Institution of Washington 2000-present
  • Lunar and Planetary Institute, Student Intern, June ? August, 1986

Awards and Achievements 

  • Fellowship recipient Memorial University of Newfoundland, Sept. 1987 - Aug. 1989
  • New York State Regents Scholarship June 1981
  • National "A" rating from the United States Pony Club, Sept. 1984
Publications
  • Ashwal, L. D., Webb, S. J., and Knoper, M. W. 2005 Magmatic stratigraphy in the Bushveld northern lobe: continious geophysical and mineralogical data from the 2950m Bellevue drillcore. S. Afr. J. Geol., 108: 195-228
  • Webb, S. J., Cawthorn, R. G., Nguuri, T. K., and James, D. E. 2004 Gravity modeling of Bushveld Complex connectivity supported by Southern African Seismic Experiment results. S. Afr. J. Geol., 107: 207-218.
  • Tredoux, M. and Webb, S. J. 2004 Research capacity building in Africa as part of international programmes: Experience gained from the K pv l Craton project. S. Afr. J. Geol., 107: 9-14
  • Burke, K., Ashwal, L. D., and Webb, S. J., 2003. A new way to map old sutures using deformed alkaline rocks and carbonatites. Geology. 31: 391-394
  • Cawthorn, R.G. and Webb, S.J., 2001. Connectivity between the western and eastern limbs of the Bushveld Complex. Tectonophysics, 330: 195-209.
  • Cawthorn, R.G., Cooper, G.R.J. and Webb, S.J., 1998a. Connectivity between the western and eastern limbs of the Bushveld Complex. S. Afr. J. Geol., 101(4): 291-298.
  • Hart, R.J., M.A.G. Andreoli, M. Tredoux, D. Moser, L.D. Ashwal, E.A. Eide, S.J. Webb, and D. Brandt, 1997. Late Jurassic age for the Morokweng impact structure, southern Africa. EPSL, 147: 25-35.
  • Green, R.W.E., Webb, S.J. and Wright, C., 1995. Broad-Band Seismic Studies in southern Africa. S. Afr. Jour. Sci., 91: 234-239.
  • James, D.E., Fouch, M.J., VanDecar, J.C., van der Lee, S. and Group, K.S., 2001. Tectospheric structure beneath southern Africa. Geophys. Res. Lett., 28(13): 2485-2488.
  • Nguuri, T.K., J. Gore, D.E. James, S.J. Webb, C. Wright, T.G. Zengeni, O. Gwavava, J.A. Snoke, and K.S. Group, 2001. Crustal structure beneath southern Africa and its implications for the formation and evolution of the K pv l and Zimbabwe cratons. Geophys. Res. Lett., 28(13): 2501-2504.
  • Zolensky, M.E., Webb, S.J., and Thomas, K. 1988. The search for refractory interplanetary dust particles from preindustrial aged Antarctic ice. Proc. 18th Lunar Planet. Sci. Conf., pp. 599-605

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