Pradeep Talwani

Professor of Geophysics
Director, South Carolina Seismic Network

B.Sc. (Honors), 1961, M.Sc. and AISM, 1962, Indian School of Mines
M.S., 1971, Ph.D., 1973, Stanford University

Research Areas: I am engaged in a broad range of research topics, using a dual approach, field studies in South Carolina and models and analyses, globally. The research topics include reservoir induced seismicity, fluid pressure flow in crystalline rocks, seismotectonics and neotectonics of stable continental regions, strain rate measurement using GPS, paleoseismology, crustal structure of the South Carolina Coastal Plain, the Charleston earthquake of 1886, seismic hazard analysis and seismicity of South Carolina. Recently acquired potential field data suggest the presence of a buried meteorite impact crater in northeast South Carolina. During the past five years our efforts have been focused on the following topics:

Reservoir Induced Seismicity (RIS): Locally we continue to monitor RIS at three locations in South Carolina. We have analyzed RIS at Koyna, India and in China and Brazil. Using seismicity patterns, stress measurements, and lake levels we have developed models to explain the nature of RIS. In most cases the RIS follows impoundment or rise in water levels over previous maximum, however at other locations seismicity continues for years. This protracted RIS is relatable to the amplitude and frequency of lake level changes. We have discovered that fractures associated with RIS have a characteristic (~ 2 - 200 mD) “seismogenic” permeability.

Fluid Pressure Flow Through Fractures: By monitoring water levels in Bad Creek Reservoir and in an observation well connected to it by a 250 m long, 1 m wide shear zone we have made probably the first in situ determination of hydraulic diffusivity in a fracture. The pore pressure diffusion was found to decay exponentially and show frequency dependence. The data allowed for an in situ permeability estimation of the shear zone (~ .1 mdarcy).

Seismotectonics of Stable Continental Regions (SCR): The results of paleoseismological research (see below), strain measurements, historical and current seismicity suggest that there are pockets of high strain located within SCR. Our proposed intersection model explains these observations. In this model intersection of faults and zones of weakness in the brittle crust provides a means to focus and accumulate stress in the ambient plate tectonic stress field. The stress accumulation rate is about two orders or magnitude greater than the plate as a whole, accounting for the short return periods (~ 500 years) for moderate earthquakes. The model predicts localized pockets of high strain rate accumulation in the continental interiors, a prediction that is being borne out as new data are gathered.

Neotectonics in SCR: We use direct and indirect observations to deduce ongoing neotectonic activity in SCR. These include GPS (see below), stream geomorphology, observations in the Charleston area, seismicity, stratigraphy, relevelling and paleoseismology. Subtle uplift in the Coastal Plain has led to the discovery of a > 200 km long Zone of River Anomalies (ZRA).

Strain Accumulation in the Charleston, South Carolina Region: By occupying 1930 circa triangulation sites and 1980 GPS sites with GPS instruments in 1993-94, 1999, and 2000 we have discovered that localized strain rate accumulation is occurring at a rate of about 0.02 x 10^-7 strain/yr. The direction of maximum compression was found to be N60°E in agreement with seismicity and borehole data.

Paleoseismology: Following the discovery of the first paleoliquefaction feature in eastern United Stated by John Cox of USC in 1983, over 100 other locations have been discovered in the South Carolina Coastal Plain by scientists from USC, U.S. Geological Survey and Ebasco Services. We have re-analyzed all data and established that there were at least 7 prehistoric earthquakes, similar to the 1886 earthquake in the past 6000 years. Based on the four recent ones, we estimate a recurrence time of about 500 years for such events.

Crustal Structure of the South Carolina Coastal Plain: By carrying out detailed gravity surveys and combining the data with aeromagnetic and seismic reflection data we have delineated several buried faults and basins under the Coastal Plain. Recent gravity investigations by Eric Wildermuth have led to the discovery of a buried meteor impact crater in northeastern South Carolina. Data for gravity bases have been recompiled and a new gravity map has been made for the Coastal Plain of South Carolina.

The 1886 Charleston Earthquake: The exact cause and nature of the large 1886 earthquake that was felt over 2 M square miles is still a subject of research. We are analyzing the 1886 observations in light of our current understanding of the crustal structures, seismicity and propagation characteristics. Hypocentral locations have been used to locate the seismogenic Ashley River and Woodstock faults thought to be responsible for the ongoing seismicity near Charleston.

Seismic Hazard Analysis in South Carolina: This is a new project aimed at assessing the seismic hazard in South Carolina using our current understanding of the seismotectonics, seismicity and recurrence rates. We have carried out Cone Penetrometer and Standard Penetration Tests in paleoliquefaction features. Currently we are working with the Soil Mechanics Lab in the School of Engineering to analyze the engineering properties of soil samples. The aim to obtain calibration data needed to estimate liquefaction potential in the Coastal Plain.

Seismic Activity in South Carolina: We continue to monitor and analyze seismic activity on the South Carolina Seismic Network. (Click on South Carolina Seismic Network for details of current and past seismicity).

Selected Publications:

Trenkamp, R., and Pradeep Talwani, GPS Derived Strain and Strain Zonation near Charleston, South Carolina. Journal of Geophysical Research, (In Review), 2005.

Leon, E., Gassman, S. L., and Pradeep Talwani, Accounting for soil aging when assessing liquefaction potential. Journal of Geotechnical and Geoenvironmental Engineering, (In Review), 2005.

Leon, E., Gassman, S. L., and Pradeep Talwani, Effect of Soil Aging on Assessing Magnitudes and Accelerations of Prehistoric Earthquakes. Earthquake Spectra, (In Press), 2005.

Abhijit Gangopadhyay, and Pradeep Talwani, Fault intersections and intraplate seismicity in Charleston, South Carolina: Insights from a 2-D numerical model. Current Science, (In Press), 2005.

Ronald Marple, and Pradeep Talwani, Proposed Shenandoah Fault and East-Coast Stafford Fault System and their implications for Eastern U.S. Tectonics. Southeastern Geology, 43, 57 - 80, 2004.

Abhijit Gangopadhyay, John Dickerson and Pradeep Talwani, A two-dimensional Numerical Model for current seismicity in the New Madrid Seismic Zone. Seis. Res. Lett., 75, 406 - 418, 2004.

Donald Stevenson and Pradeep Talwani, 2001 - 2002 Upper Three Runs Sequence of Earthquakes at the Savannah River Site, South Carolina. Seis. Res. Lett., 75, 107 - 116, 2004.

Abhijit Gangopadhyay and Pradeep Talwani, Symptomatic Features of Intraplate Earthquakes. Seis. Res. Lett., 74, 863 - 883, 2003.

Pradeep Talwani, Eric Wildermuth and Chris D. Parkinson, An Impact Crater in Northeast South Carolina Inferred from Potential Field Data. Geophys. Res. Lett., 30(7), 1366, doi:10.1029/2003GL017051, 2003.

Martin C. Chapman, Pradeep Talwani, and Richard C. Cannon, Ground-Motion Attenuation in the Atlantic Coastal Plain near Charleston, South Carolina. Bull. Seis. Soc. Am., 93, 998 - 1011, 2003.

Ke Hu, Sarah L. Gassman and Pradeep Talwani, Magnitudes of Prehistoric Earthquakes in the South Carolina Coastal Plain from Geotechnical Data. Seis. Res. Lett., 73, 979-991, 2002.

Ke Hu, Sarah L. Gassman and Pradeep Talwani, In-situ Properties of Soils at Paleoliquefaction Sites in the South Carolina Coastal Plain. Seis. Res. Lett., 73, 964-978, 2002.

Thomas G. Hildenbrand, W. D. Stuart and Pradeep Talwani, Geologic Structures related to New Madrid earthquakes near Memphis, Tennessee, based on gravity and magnetic interpretations. Engg. Geol., 62, 105-121, 2001.

Pradeep Talwani and Abhijit Gangopadhyay, Tectonic Framework of the Kachchh earthquake of 26 January 2001. Seis.Res.Lett., 72, 336-345, 2001.

Pradeep Talwani and William T. Schaeffer, Recurrence rates of large earthquakes in the South Carolina Coastal Plain based on paleoliquefaction data. J. Geophys. Res., 106, 6621-6642, 2001.

Linyue Chen and Pradeep Talwani, Mechanism of Initial Seismicity Following Impoundment of the Monticello Reservoir, South Carolina. Bull. Seis. Soc. Am., 91, 1582-1594, 2001.

Linyue Chen and Pradeep Talwani, Renewed Seismicity near Monticello Reservoir, South Carolina, 1996-1999. Bull. Seis. Soc. Am., 91, 94-101, 2001.

Ronald T. Marple and Pradeep Talwani, Evidence for a buried fault system in the Coastal plain of the Carolinas and Virginia - Implications for neotectonics in the southeastern United States. Bull. Geol. Soc. Am., 112, 200-220, 2000.

Pradeep Talwani, Seismogenic properties of the crust inferred from recent studies of reservoir-induced seismicity - Application to Koyna. Current Science, 79, 1327-1333, 2000.

Pradeep Talwani, Jason S. Cobb and Malcolm F. Schaeffer, In Situ Measurements of Hydraulic Properties of a Shear Zone in Northwestern South Carolina. J. Geophys. Res., 104, 14,993-15,003, 1999.

Pradeep Talwani and Navin Sharma, Re-evaluation of the Magnitudes of Three Destructive Aftershocks of the 1886 Charleston Earthquake. Seis.Res.Lett., 70, 360-367, 1999.

Pradeep Talwani, Fault Geometry and Earthquakes in Continental Interiors. Tectonophysics, 305, 371-379, 1999.

Linyue Chen and Pradeep Talwani, Reservoir Induced Seismicity in China. Pure and Applied Geophysics, 153, 133-149, 1999.

Pradeep Talwani, On the Nature of Reservoir-Induced Seismicity. Pure and Applied Geophysics, 150, 473-492, 1997.

Pradeep Talwani, Seismotectonics of the Koyna-Warna Area, India. Pure and Applied Geophysics, 150, 511-550, 1997.

Pradeep Talwani and Ronald T. Marple, Evidence of Neotectonic Activity in the South Carolina Coastal Plain. Proc. 30th Int’l. Geol. Congr., Vol. 5, 49-61, 1997.

D.A. Stevenson and Pradeep Talwani, Aiken Earthquake of August, 1993. Seis. Res. Letters, 67, 43-50, 1996.

Pradeep Talwani, Two categories of Reservoir Induced Seismicity in Proceedings of International Symposium on Reservoir Induced Seismicity, 44-64, Beijing, China, 1995.

Pradeep Talwani and David Amick, Study of Paleoliquefaction Features for Seismic Hazard Assessment International School of Solid Earth Geophysics, 11th Course. Active Faulting Studies for Seismic Hazard Assessment, (Extended Abstract). Eds. G. Valensise and D. Pantosti, 9 pgs., Erice, Sicily, Italy, September 1995.

C.P. Rajendran and P. Talwani, Paleoseismic Indicators Near Bluffton, South Carolina: An Appraisal of Their Tectonic Implications. Geology, 21, 987-990, 1993.

Marple, R.T. and Talwani, P., Evidence of Possible Tectonic Upwarping Along the South Carolina Coastal Plain From an Examination of River Morphology and Elevation Data. Geology, 21, 651-654, 1993.

Madabhushi, S. and Talwani, P., Composite Fault-Plane Solutions and Relocations of Recent Earthquakes Near Charleston, South Carolina. Bull. Seis. Soc. Am. , 83, 1442-1466, 1993.

Rajendran, K., and Talwani, P., The Role of Elastic, Undrained, and Drained Responses in Triggering Earthquakes at Monticello Reservoir, South Carolina. Bull Seis. Soc. Am., 82, 1867-1888, 1992.

Talwani, P. and Rajendran, K., Some Seismological and Geometric Features of Intraplate Earthquakes. Tectonophysics, 186, 19-41, 1991.

Bollinger, G.A., Johnston, A.C., Talwani, P., Long, L.T., Shedlock, K.M., Sibol, M.S. and Chapman, M.C., Seismicity of Southeastern United States 1698-1986; In: Neotectonics of North America, Slemmons, et al (eds), p. 291-308, 1991.

Talwani, P., Neotectonics in the Southeastern United States With Emphasis on the Charleston, South Carolina, Area. In: Krinitzsky, E.L., and Slemmons, D. B., "Neotectonics in earthquake evaluation: Boulder, Colorado," Geological Society of America Reviews in Engineering, V. 8, p. 111-129, 1990.

Talwani, P., Characteristic Features of Intraplate Earthquakes and the Models Used to Explain Them. In: "Earthquakes at North-Atlantic Passive Margins: Neotectonics and Post-glacial Rebound," S. Gregersen and P. Basham, eds., NATO ASI series. Series C, Mathematical and Physical Sciences, 226, 229-235, 1989.

Talwani, P., The Intersection Model for Intraplate Earthquakes. Seis. Res. Lett., 59 (4), 305-310, 1988.

Poley, C.M., and Talwani, P., Vertical Tectonics in the Charleston, South Carolina, Area. J. Geophys. Res., 91, 9056-9066, 1986.

Talwani, P., and Acree, S., Pore Pressure Diffusion and the Mechanism of Reservoir-Induced Seismicity. Pageoph, 122, 947- 965, 1984.

Talwani, P., Internally Consistent Pattern of Seismicity Near Charleston, South Carolina. Geology, 10 (12), 654-658, 1982.

Pradeep Talwani
Department of Geological Sciences
University of South Carolina
Columbia, South Carolina 29208

Telephone: (803) 777-6449

FAX: (803) 777-6610

E-mail: talwani@geol.sc.edu

Last Updated August 20, 2007 by tappa@geol.sc.edu
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