3-D crustal shear wave velocity model derived from full-waveform tomography for Central Honshu Island, Japan

Abstract

SUMMARY We present a crustal shear wave (S-wave) velocity model for central Japan that accurately captures the previously mapped geology and lithology of the region. We perform a full-waveform tomographic inversion using a large seismic data volume that was recorded by the dense, permanent seismic monitoring network that spans the Japan Islands to resolve the seismic structure beneath central Honshu Island. The inversion reduces the time–frequency phase misfit by 16.4 and 6.7 per cent in the 20–50-s and 10–30-s period ranges, respectively. We infer that the resolved seismic velocity anomalies in our inversion reflect a range of subsurface features, including volcanic fluids, dehydration fluids from the subducted crust and sedimentary basins. In contrast to previous S-wave velocity models of the same region, which have been based primarily on first-arrival tomography, our S-wave velocity model is based on the explicit computation of the full seismic wavefield. This approach makes our model more suitable for modelling seismic wavefields in the 10–50-s period range and enables high-resolution imaging of the subsurface.