The program surf96 is used to invert for a model that better fits the observed dispersion. The initial model is that used by the University of Utah Seismograph Stations locations of earthquakes in the Yellowstone area:
The resultant model is Revised Yellowstone Model
The inversion preserves the layer discontinuities of the initial model, but slightly perturbs the velocities in the layers. The models and fit to observed dispersion and anelastic attenuation are
Model and anelastic attenuation fit
It is always interesting to see how these different models would affect the travel time measurements which are used for location. The following figure compares the predicted first P-wave arrival times for the two models for a surface focus using the program timmod96. The first arrival time are very similar out to the Pn arrival.
The real difference is that this model better predicts the transverse component seismograms and does better with the Rayleigh wave on the Z and R traces than does the CUS model.
Comparison of observed and predicted broadband traces
