Susan Jane Webb
Susan Jane Webb originates from upstate New York and received her BSc in geophysics from SUNY Binghamton and her MSc in geophysics from Memorial University in Newfoundland. In search of warmer weather and adventure, she moved to South Africa and worked for several years as an exploration geophysicist for Gold Fields of South Africa. Currently she is an Associate Professor in the School of Geosciences at the University of Witwatersrand in Johannesburg, South Africa . As a full-spectrum educator, not only does she supervise undergraduate, M.S., and Ph.D. students but she also leads her university’s geophysical field camp and collaborates with Pennsylvania State University in the AfricArray Partnership, using seismological stations throughout Africa as a basis to teach geophysics. This field school hosts selected students from all over Africa and the world. In 2005 she was awarded the Jubilee Medal from the Geological Society of South Africa for the best paper in the South African Journal of Geology. In 2006 her technical presentation at the SEG meeting in New Orleans was cited as one of the top 30 papers. In 2007 she was elected as a Fellow of the GSSA. Sue is active in SEG and SAGA, is currently vice chairman of the SEG Global Affairs Committee, and was a founding committee member for the SEG initiative Geoscientists Without Borders.
Biography Citation for SEG Outstanding Educator Award 2014
Contributed by Louise Pellerin
Sue Webb has been an educator as long as she has been a student and has often interchanged the roles. She received a B.S. in geophysics at the State University of New York–Binghamton (SUNY) in 1986 and an M.S. in geophysics from Memorial University of Newfoundland, Canada, in 1992. During that time, she worked as a teaching and research assistant, nurturing her tremendous skills as an educator. A position at Gold Fields of South Africa started her on a lifetime adventure across the globe. After four years, she joined the School of Geosciences at the University of the Witwatersrand (Wits) as a lecturer. She completed a Ph.D. there in 2009 and became a senior lecturer in 2010.
Wits is a university with aspects that well complement Sue — a long-respected tradition in mineral exploration and teaching students from extremely diverse backgrounds. Sue can switch from working with a graduate student on a complex geophysical problem to patiently explaining a very simple computer hurdle to an inexperienced student with ease and grace. She is the driving force behind the AfricaArray Geophysical Field School, where she not only teaches the principles of data acquisition but also how to feed and take care of yourself in the bush.
Being an educator doesn’t stop at the university, however. As the SEG Middle East and Africa Honorary Lecturer, Sue was an outstanding role model for women and men alike. As the lead on a Geoscientists Without Borders project, helping to find water at a rural school outside Johannesburg, she served to inspire children and to teach them about the earth. She has given South African radio and television interviews to educate the general public about current earth-science events.
Sue’s enthusiasm for the earth sciences is contagious, her energy is unbridled, and her laugh is appreciated by all who know her. All these aspects make Sue an outstanding educator and a fitting recipient of the first SEG Outstanding Educator Award.
2010 SEG Honorary Lecturer, Middle East and Africa
Deep gravity-long wavelengths and measured moho
In most interpretations of gravity data, the long wavelength gravity signal (~100 km) is ignored and assigned to the dust bin of the "regional anomaly." If the long wavelengths are considered at all, they are generally "cheaply and cheerfully" removed by inverting topography in a simplistic isostatic correction that assumes a Moho that mirrors the topography. Using the isostatic gravity anomaly often clarifies near-surface geological features of interest. However, this simplistic method has serious flaws for larger-scale features. From several data compilations, it is apparent that the Moho does not mirror the surface topography and that the uppermost mantle may have significant density variations, resulting in gravity anomalies of similar wavelengths. Thus, simplistic isostatic corrections are naïve at best and at worst can lead to serious misinterpretations for mid- to large-scale gravity modeling. With the advent of 3D gravity modeling, it is now becoming possible to model large-scale targets and to consider these regional effects in more detail. As a result of the Kaapvaal Project, we now have unprecedented coverage of the crustal thickness and details of the seismic velocity variations in the lithosphere beneath southern Africa. By using these data, we can calculate the contribution of each component to the overall gravity field. Keeping in mind that a large sedimentary basin such as the Karoo, or an important PGE deposit such as the Bushveld complex, may extend well over 400 km laterally, full and proper account of the Moho and upper mantle density variations may significantly alter the modeling result and lead to possible targets.
A recording of the lecture is available.