Using Shear Wave Travel Time Correction Surfaces to Improve Regional Seismic Location in China


Generation of Propagation Path Correction (PPC) Surfaces

We have developed IASP91 shear wave propagation path correction (PPC) surfaces for use with the EvLoc [Bratt and Bache, 1988; Nagy, 1996] location algorithm. Using the shear wave data set from Figure 2 (EDR and LANL Regional databases), PPCs were constructed from travel time residuals for events that met the following:
  • 30 or more defining phases
  • Azimuthal gap less than 180°
  • | Residual | ¾ 10 seconds
Corrections surfaces were constructed using modified Bayesian kriging [Schultz, et. al., 1998] which provides well-behaved interpolants, but requires adequate error estimates associated with the travel time residuals. Shear wave PPCs were developed for 72 stations from 667 events which had S phases meeting the above criteria.

Figure 3 - Events with S phases which met the criteria for generating shear wave PPC surfaces.

Figure 4 - Example Shear Wave PPC Surfaces for IASP91 (seconds)


Introduction | Generation of Propagation Path Correction (PPC) Surfaces | Ground Truth Comparisons
Ground Truth Comparisons Using LANL S Picks | Focal Mechanism Comparison | Conclusions and Future Work | References