2.3 Event relocation
The accuracy and reliability of seismic tomography are also dependent on the quality of the location results of the earthquakes, which may contain significant uncertainties since they are often obtained from routine event determinations based on 1-D Earth models. To minimize the biases in our tomography introduced by event location errors, we adopt an iterative inversion process during which the 3-D P-wave velocity model obtained from our inversion is used to relocate all of the contributing events. The relocation uses P-wave travel times calculated in the 3-D model by the multi-stage fast marching method (de Kool et al., 2006) and the neighbourhood algorithm (Sambridge and Kennett, 2001) in a global search for the hypocenters.