Applications of GPS seismology in the Japanese region

To explore the possibilities of using GPS waveforms in seismology, high-rate GPS data recorded after a number of large earthquakes are processed with GAMIT and three-component displacement waveforms are calculated. GPS waveforms are capable of recording the waveforms of passing surface waves whenever the ground displacement exceeds the noise level of the GPS observations (2-3 mm). In this study, these waveforms are used to invert for the moment tensor source of the earthquakes under the point source approximation. It is concluded that GPS waveforms recorded in the near-field of an event with a magnitude larger than Mw = 6.5 are capable of estimating the magnitude and the mechanism of the earthquake. Case studies from Japan show that using standard seismological methods with GPS data it is possible to characterise earthquake sources. If GPS observations are available in real time, they have the potential to contribute to rapid solutions of earthquake source inversions.

Since the GPS waveforms agree well with synthetic seismograms and they are capable to model the source of the earthquake, by extension they have the potential to contribute to seismic tomography models. Preliminary results of a regional seismic tomography model have been compuded, that is the starting point towards including GPS data in the next generation of seismic tomography models.