Optional Inter-Station Constraint
- We can assume that the travel times are similar for waves that follow similar paths and use this knowledge to constrain the arrival times.
- Before tomographic inversion, we find the best (i.e. maximum likelihood) estimate of the arrival times based on the observed times and the difference between times of waves traveling along similar paths.
- This is not always needed, but does a good job of reducing the influence of errors that are large between stations, but not large enough to be rejected.
- When used in areas with large-area velocity anomalies it can introduce pattern sensitive false anomalies.