Dr. James N. Kellogg

Professor, Applied Geophysics
Director of Andean Geophysical Laboratory
Editor-In-Chief, Journal of South American Earth Sciences , Elsevier Press

B.A., 1966, Northwestern University;
M.A., 1978, Ph.D., 1981 Princeton University;

Research Areas: Applied geophysics, GPS geodesy, gravity/tectonic studies, tectonics of active margins, Andean orogenic belt, GIS, seamounts, 3D seismic intrepretation.

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Photos from Morocco

Measuring Andean Plate Motions with Satellite Geodesy:

Portable receivers using signals from satellites of the Global Positioning System (GPS) have greatly expanded our ability to make precise geodetic measurements. These measurements are yielding contraints on plate motion models, behavior at plate boundaries, and intraplate deformation. As the lead U.S. academic institution in the 14-year NSF/NASA funded CASA (Central And South America) GPS Project, USC is taking a leading role in this exciting new technology. In 1988, 1990, 1991, 1994 scientists in 34 countries cooperated in the world's largest GPS campaigns and the first civilian global tracking networks. Additional field campaigns were conducted in 1996, 1998 and 1999, and 2001, with plans currently for an expanded continuous GPS network to analyze the on-going convergent margin deformation associated with the earthquake cycle.

With NASA-developed GIPSY software, USC graduate students are routinely calculating precise satellite orbits and long baselines (up to 1000 km) with subcentimeter-level precision Several of the most exciting results were the first direct measurement of the convergence rates for rapidly subducting trenches and the divergence rate for an oceanic spreading center. In 2001 the 1,323 km baseline from Baltra in the Galapagos Islands to Jerusalen in the Andes was approximately 80 cm shorter than it was in 1988. The relative motions of the larger plates are in agreement with the predictions of global plate motion models. However, deformation in the wide plate boundary is not addresses by the models.

GPS measurements show that the rigid Panama microplate is colliding eastward with the Northern Andes at about 30 mm per year, the Northern Andes are moving approximately 6 mm per year northeastward relative to stable South America, and slow amagmatic Caribbean subduction beneath the Northern Andes (10-15 mm per year).

Integrated Tectonic-Geophysical Basin Studies:

Andean Forearc, Inter-Andean, and Foreland basins are characterized by complex compressional structures that often involve crystalline basement rocks. The approach being used in these basin studies is to develop volume-balanced structural models, based on the surficial geology, well logs, and seismic reflection profiles. The balanced geological models are then iteratively modified to satisfy the potential field data.

Gravity and magnetic studies can play an important role in the initial as well as ongoing assessment of basin structure. Potential field data can provide the regional setting for basins and constrain models of deep basin geometry, especially in areas of basement-involved deformation. For example, we used the gravity and magnetic fields to predict the depth of the Cretaceous Basin within the Colombian Eastern Cordillera and marginal structures, a critical problem for interpretation of the structural evolution and prospectivity of the mountain range.

Graduate students have been funded by the Petroleum Research Fund of the American Chemical Society, and industrial sponsors.

Guinea Equatorial Geoscience Project

Kellogg is Principal Investigator for Guinea Equatorial Geoscience Project GEGEO (Guinea Equatorial GEOscience progra m) that provides for technical and scientific cooperation between the National U niversity of Equatorial Guinea (UNGE) and the University of South Carolina (USC) . In September 2003 the GEGEO Program began in Malabo, Equatorial Guinea, enroll ing 22 students in a three year geotechnical degree program. Faculty associated with USC have joined with faculty from UNGE to develop and teach basic science w ith an emphasis on geosciences as well as increased facility with the English la nguage. Selected students from this program complete a Bachelor of Science degre e in Geological Sciences at the University of South Carolina. It is envisioned t hat UNGE will become an education center helping to meet the growth needs in the regional petroleum and mining industries in Equatorial Guinea, as well as for o ther central west African states, such as Nigeria, Cameroon, Ivory Coast, Angola , and Gabon.

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