HR: 0800h
AN: S51B-0503    [Abstracts]
TI: Application of the Back-Projection Technique to Large Earthquakes Using the Hi-net Data
AU: * Kiser, E
EM: kiser@fas.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St., Cambridge, MA 02138, United States
AU: Ishii, M
EM: ishii@eps.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St., Cambridge, MA 02138, United States
AU: Shearer, P M
EM: pshearer@ucsd.edu
AF: Institute of Geophysics and Planetary Physics, University of California, San Diego, 8800 Biological Grade, La Jolla, CA 92093, United States
AB: The High Sensitivity Seismograph Network (Hi-net) is one of the world's finest seismographic networks, consisting of more than 700~stations distributed throughout Japan. Its borehole instrumentation ensures high- quality data, and provides an opportunity for investigating characteristics of earthquakes in detail. This is achieved empirically by stacking the seismograms at potential locations of energy radiation using a back- projection method, and studying the coherence and amplitude of the stacks as a function of space and time. The technique has been successfully applied to the December 26, 2004 Sumatra-Andaman and March 28, 2005 Nias earthquakes, providing constraints on their rupture speed, duration, extent, direction, area, and spatio-temporal variations. One unique feature of the back-projection approach for studying earthquake characteristics is that it can be performed in near realtime, as soon as the first-arriving seismic waves are recorded at the Hi-net stations. The Hi-net data are available from October 2000. Since then, there have been more than 20~earthquakes larger than magnitude~7.8 that are good candidates to be studied using the back-projection method. We investigate the characteristics of these events and explore the capabilities and limitations of the back-projection technique. The resolvability of rupture depends on the source location with respect to Japan, which has consequences for the method's applicability for near realtime analysis. We also expand the source grid to allow variations in depth; our previous studies on the two Sumatran earthquakes have assumed horizontal slip planes, which is inaccurate for many events.
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2007 Fall Meeting