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Charles J. Ammon |
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Research [ Publications ]
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Research: My research is focussed on earthquake seismology, using the information recorded in seismograms to study earthquake processes and Earth structure. I have worked on modeling moderate-size (magnitudes 4 to 5) earthquakes to estimate faulting parameters (such as strike, dip, rake, and moment) and depth in the eastern United States (in collaboration with Bob Herrmann) as well as regions with higher rates of seismic activity such as Tibet and the Tien Shan region of Eurasia. At the other end of the earthquake size spectrum are the large earthquakes (magnitudes larger than 7). These larger earthquakes are more complicated and in addition to esti-mating the depth, size, and faulting geometry we can study the character of the fault rupture (how large an area of the fault slipped? How fast and in what direction did the rupture travel? How much did the fault slip? etc.). In collaboration with researchers from several institutions I have investigated the rupture character of about ten major and great earthquakes which occurred during the last few years. Work is underway with one of our current students, Luca Malagnini, to study three recent large earthquake sequences that occurred in the subduction zone off the coast of Kamchatka. In addition to earthquake studies, I am involved in studies of Earth structure including studies of surface-wave propagation across the North America plate (in collaboration with Harley Benz of the US Geological Survey) and across the Arabian plate (in collaboration with Bob Herrmann and Talal Mokhtar of Saudi Arabia). This work includes the analysis of surface-wave dispersion and the use of tomographic techniques to image lateral variations in the lithospheric structure. Juan-Pablo Ligorría and I have also completed a survey of the nature of the crust-mantle boundary beneath more than 100 sites in North America. We are correlating our results with geological history of each region trying to understanding the interaction between crust and mantle during the evolution of the continent. Research Collaborators: Current students: Juan-Pablo Ligorría, Brett Ketter and Rommel Villagómez. Recent collaborators from other institutions: George Zandt, University of Arizona; Aaron Velasco and George Randall, Los Alamos National Laboratory; Thorne Lay, University of California at Santa Cruz; Harley Benz, US Geological Survey; Sujoy Ghose and Michael Hamburger, University of Indiana. Selected Publications Ligorría J. P. and C. J. Ammon (1998). Iterative Deconvolution and Receiver-Function Estimation, in press the Bulletin of the Seismological Society of America. Ammon, C. J., R. B. Herrmann, C. A. Langston, and H. Benz (1998). Source parameters of the January 16, 1994 Wyomissing Hills, Pennsylvania earthquakes, Seismological Research Letters, 69, 261-269. Randall, G. R., C. J. Ammon, and T. J. Owens (1995). Moment-tensor estimation using regional seismograms from a Ti-betan Plateau portable network deployment, Geophysical Research Letters, 22, 1665-1668. Velasco, A. A., C. J. Ammon, and T. Lay (1995). Source time function complexity of the great 1989 Macquarie Ridge earthquake, Journal of Geophysical Research, 100, 3989-4009. Zandt, G. and C. J. Ammon (1995). Continental Crustal composition constrained by measurements of crustal Poisson's ratio, Nature, 374, 152-154. Ammon, C. J., A. A. Velasco, and T. Lay (1993). Rapid estimation of rupture directivity: Application to the 1992 Landers (Ms = 7.4) and Cape Mendocino (Ms = 7.2) California Earthquakes, Geophysical Research Letters, 70, 97-100. Velasco, A. A., C. J. Ammon, T. Lay, and J. Zhang (1994). Imaging a slow bilateral rupture with broadband seismic waves: The September 2, 1992 Nicaragua Tsunami Earthquake, Geophysical Research Letters, 21, 2629-2632. Ammon, C. J., G. E. Randall, and G. Zandt (1990). On the non-uniqueness of receiver function inversions, Journal of Geophysical Research, 95, 15303-15318. |
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