We relocate historic Groningen gas field events that have occurred before year 2000. These events have been recorded by a very small and sparse network of stations in the area with a fairly complicated velocity model. Events are relocated using publicly available P-wave pick arrivals, and a version of the velocity model provided by the operator, the Nederlandse Aardolie Maatchappij (NAM), that we have smoothed. We use station corrections, calculated using a different set of more recent events recorded by a larger array of receivers, to correct the model and diminish apparent biases. The new locations appear to exhibit more structure that suggests presence of active faults.
