DALE S. SAWYER Professor of Geology and Geophysics Vice Chair of the Department of Geology and Geophysics Research Interests: Geodynamics and Seismology More Information About Dale Sawyer Tel (713) 285-5106 Fax (713) 285-5214 Email dale@rice.edu

Research | Publications | Graduate Students

RESEARCH:
My research focuses on the dynamic processes which have created continental margins. I use two tools in my studies: geodynamic modeling and wide-angle ocean bottom seismology. Geodynamic models of the rifting of continental lithosphere are not explaining many previously enigmatic observations at divergent continental margins. I use the finite element method running on a variety of machines up to supercomputer class to simulate the plate tectonic deformation of the upper 125 km of the earth. Along with a colleague at Rice, I have recently published a model which can explain why the character (location and style of rifting) of some rifts (including the US Atlantic margin and Australian Exmouth Plateau margin) changes during rifting from so called "simple" shear to "pure" shear.

I also use Ocean Bottom Seismometers to acquire wide-angle seismic data on divergent and convergent continental margins. Wide-angle seismic data are obtained when receivers are located both close to the shots, as in the more typical near-offset seismology, and also far from the shots. The data at a range of offsets (the distance between shot and reciever) are very useful for determining the velocity of sound waves in rocks, and from that identify the type of rocks, at great depth (up to about 40 km in the experiments I have done). During the last five years, I have been involved in field work in Cook Inlet Alaska, offshore South Carolina, Georgia and Florida, the Gulf of Mexico, and Antarctica. I have data from those cruises that can be used by my students, and I plan to continue acquiring these type of data.

PUBLICATIONS:

• "AVO analysis of low velocity, shallow sands (<50 m)", Society of Exploration Geophysicists Abstracts with Programs, (1997), with J.H. Bradford and C.A. Zelt.

• "The Iberia Seismic Experiment: Multichannel Seismic Reflection Profiles," Transactions of the American Geophysical Union 78, (1997) 468-469, with T. Reston, M.P. Gusinye, C. Zelt, J.A. Austin, Y. Nakamura, J. Danobietia, and D. Cordoba.

• "The Iberia Seismic Experiment: Wide-Angle Ocean Bottom Data," Transactions of the American Geophysical Union 78, (1997) 469, with C. Zelt, T. Reston, Y. Nakamura, and S. Ye.

• "Gravity Inversion Methods for determining the deep structure of rifted margins," Transactions of the American Geophysical Union 78, (1997) 659, with F. Condi, C. Zelt, and G. Hirasaki.

GRADUATE STUDENTS:

• John Bradford, Ph.D - Interests: Acquisition and processing of shallow seismic reflection data (<500 m) in glacial and glacial-marine sediments.

• Laurel Kirkland, Ph.D. - Interests: Studying the iron mineralogy of Mars

• Frank Condi, Ph.D. - Subsidence history and rifting dynamics of Atlantic continental margins

• Mike Unger, M.A. - Processing and Interpretation of MCS and OBS seismic data collected offshore Portugal over the Galicia Bank during the summer of 1997

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