Professor, Applied Geophysics
Director of Graduate Studies
Director of Andean Geophysical Laboratory
B.A., 1966, Northwestern University;
M.A., 1978, Ph.D., 1981, Princeton University
Research Areas: Applied geophysics, GPS geodesy, gravitytectonic studies, tectonics of active margins, Andean orogenic belt, GIS, seamounts.
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 constraints on plate motion models, behavior at plate boundaries, and intraplate deformation. As the lead U.S. academic institution in the 10-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 and 1994 scientists in 34 countries cooperated in the world's largest GPS campaigns and the first civilian global tracking networks. Observers spent long nights in wet jungles, on cold Andean peaks, and on barren rocks in the middle of the ocean to make the experiments possible.
With NASA-developed GIPSY software, USC graduate students are routinely calculating precise satellite orbits and long baselines (up to 1000 km) with centimeter-level precision and evaluating the effects of global tracking network geometries on baseline accuracy. Several of the most exciting results after the repeat GPS occupation of CASA sites were the first direct measurements of the convergence rates for rapidly subducting trenches and the divergence rate for an oceanic spreading center. In 1994 the 1323 km baseline from Baltra in the Galapagos Islands to Jerusalen in the Andes was approximately 40 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 addressed by the models.
GPS measurements show that the rigid Panama microplate is colliding eastward with the Northern Andes at about 20 mm/yr, the Northern Andes are moving approximately 6 mm/yr northeastward relative to stable South America, and slow amagmatic Caribbean subduction beneath the Northern Andes (10-15 mm/yr).
Integreted 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 are being funded by oil companies, the Petroleum Research Fund of the American Chemical Society, and the twelve industrial sponsors of the Colombian Geophysical Project.
Stress Distribution, Seismicity, and Wellbore Breakouts in the Andes: Understanding the nature and origins of the contemporary in situ stress fields in the earth's crust is needed for constraining models of tectonic processes and the driving mechanism of plate motions. One method of determining in situ stress orientations is the analysis of well bore elongations or "breakouts." Our database includes well log data from over 100 recent wells in the northern Andes. The spatial distribution of earthquake hypocenters, orientations of the principal axes of the seismic focal mechanisms, and centroid moment tensors can be used to predict the stress field and to estimate the average elastic strain. Focal mechanisms for large earthquakes in the North Andes indicate the orientations of compressive stresses responsible for Andean uplift and folding and thrusting in the foreland basins.
Freymueller, J.T., and J.N. Kellogg, 1992, Isostasy and tectonic origins of Pacific seamounts, in B. Keating and B. Bolton eds., Geology and Offshore Mineral Resources of the Central Pacific Basin, Circum-Pacific Council for Energy and Mineral Resources Earth Science Series, Vol. 14. New York, Springer-Verlag, 39-53.
Toto, E.A. and J.N. Kellogg, 1992, Structure of the Sinu-San Jacinto fold belt-An active accretionary prism in northern Colombia, Journal of South American Earth Sciences, vol. 5, no. 1, 211-222.
Freymueller, J.T., and J.N. Kellogg, 1993, Plate Motions and Active Crustal Deformation in the North Andean Region Measured with the Global Positioning System, in W. Torge, Gonzalez Fletcher, J.G. Tanner eds., Recent Geodetic and Gravimetric Research in Latin America, Springer-Verlag, Berlin-Heidelberg-New York.
Freymueller, J.T., J.N. Kellogg, and V. Vega, 1993, Plate Motions in the North Andean Region, Journal of Geophysical Research, v. 98, 21,853-21,863.
De Toni, B. and J.N. Kellogg, 1993, Seismic evidence for blind thrusting of the northwestern flank of the Venezuelan Andes, Tectonics, v. 12, 1,393-1,409.
Kellogg, J.N., 1993, Balanced geological cross-sections and prospectivity of the Alpujarra area, Sumapaz Project, Upper Magdalena Valley, Colombia, internal report, Empresa Colombia de Petroleos, Bogota, 49p., 9 plates.
Talwani, P. and J.N. Kellogg, 1994, Validation of tectonic models for an intraplate seismic zone, Charleston, South Carolina, with GPS geodetic data, Report for NRC, 9 p.
Kellogg, J.N., and V. Vega, 1995, Tectonic development of Panama, Costa Rica, and the Colombian Andes: Constraints from Global Positioning System geodetic studies and gravity, Geologic and Tectonic Development of the Caribbean plate boundary in southern Central America, GSA special paper, P. Mann, editor.
Stallings, T.C., C.L.V. Aiken, and J.N. Kellogg, 1995, Southern Central America Gravity Anomaly Map, Bouguer (Land) Free-air (Marine), scale 1:1,500,000, Geologic and Tectonic Development of the Caribbean plate boundary in southern Central America, GSA special paper, P. Mann, editor.
Dr. James N. Kellogg
Department of Geological Sciences
University of South Carolina
Columbia, SC 29208
Fax: (803) 777-6610