HR: 0830h
AN: S41B-10    [Abstracts]
TI: Effects of Near-Source Scatterers on Radiation From Seismic Sources
AU: * Chi, S
EM: shihong@erl.mit.edu
AF: Earth Resources Laboratory, Massachusetts Institute of Technology, ERL at MIT, E34-566 42 Carleton St., Cambridge, MA 02142 United States
AU: Toksöz, M
EM: toksoz@mit.edu
AF: Earth Resources Laboratory, Massachusetts Institute of Technology, ERL at MIT, E34-566 42 Carleton St., Cambridge, MA 02142 United States
AU: Zhang, Y
EM: yangz@mit.edu
AF: Earth Resources Laboratory, Massachusetts Institute of Technology, ERL at MIT, E34-566 42 Carleton St., Cambridge, MA 02142 United States
AB: The objective of this research is to study the effects of scattering from near-source heterogeneities on seismic wave radiation. High-contrast heterogeneities strongly scatter both P and S waves and later the source radiation patterns. We investigate these effects using a three-dimensional finite-difference modeling code that includes variable grid, free surface with topography, and seismic attenuation. A perfectly matched layer is incorporated into the code for improving absorption at the boundaries. Two source models are considered: an explosion and a double couple. An explosion source is placed near a finite-length tunnel. The calculations show both P to P and P to S scatterings. The tunnel acts as a secondary source with strong radiation of S waves. Love waves are observed at the surface. Then a double-couple source is placed near high impedance contrast heterogeneity. Complicated scatterings of both P and S waves are observed. In both cases the distance from source to scatterer plays an important role in scattering intensity. Moment tensor inversion of seismograms for an explosion source near a tunnel gives a source model that includes both diagonal and off-diagonal elements. For a double-couple source near a solid scatterer, the source distortion is observable, but less prominent than that of an explosion.
DE: 7212 Earthquake ground motions and engineering
DE: 7215 Earthquake parameters
DE: 7219 Nuclear explosion seismology
DE: 7255 Surface waves and free oscillations
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2005 Joint Assembly