HR: 14:15h
AN: S53D-03 INVITED    [Abstracts]
TI: Application of the Time Reversed Acoustic Concept to Earthquake Location and Focal Depth Determination
AU: * Toksoz, M
EM: toksoz@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, 54-1814, Cambridge, MA 02139, United States
AU: Lu, R
EM: lurr@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, 54-1814, Cambridge, MA 02139, United States
AU: Pearce, F
EM: fpearce@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, 54-1814, Cambridge, MA 02139, United States
AU: Sarkar, S
EM: ssarkar@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, 54-1814, Cambridge, MA 02139, United States
AB: Local and regional seismograms have long codas due to strong scattering of seismic waves in the crust. Accurate identification of individual phases (P, pP, PmP, S, sS, etc.) is difficult because the scattered arrivals complicate the local seismograms and introduce errors in picking phases and their arrival times. These, in turn, introduce errors in hypocenter parameters. Strong scattering, that is a detriment to picking individual phases, makes it possible to apply the Time Reversed Acoustic (TRA) concept to local earthquake location and focal depth determination. The basic idea in TRA is to time reverse the recorded signals (seismograms) and to inject them into the earth. If the earth structure is known, the back-propagated signals could focus at the source. We demonstrate this by synthetic (numerical) examples and with seismograms from earthquakes. Foci, determined by TRA and by traditional methods with arrival times from close-in stations, agree very well. Independently, we present a method based on the TRA concept for earthquake focal depth determination. In a highly scattering medium, the source time function determination and pP identification can be accomplished simply, by autocorrelation of the seismograms.
DE: 7215 Earthquake source observations (1240)
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2007 Fall Meeting