Schardong, L; Takeuchi, N; Kawakatsu, H; NECESSArray Project Team; (2013) Comparison of P-, SV- and SH-wave velocity models below Japan and Northeast China. Presented at: Seismological Society of Japan Fall Meeting, Yokohama, JP.

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Abstract

The recent deployment of the NECESSArray seismic network in Northeast China has allowed new insights on the velocity structure of this formerly poorly resolved area. This experiment has brought new data to debate about the geodynamical context in this region (stagnant slab, origin of intraplate volcanoes, ...). We use a more efficient method for the measurement of travel time residuals by cross-correlating observed and synthetic waveforms. Synthetic seismograms are convolved with high-frequency source-time functions inverted along with focal depths, following a simulated annealing approach. Thus, resulting modeled waveforms take more accurately account for the source effects. The method is used to perform measurements on direct P, SV and SH phases extracted from, respectively, vertical, radial and transverse band-pass-filtered records from NECESSArray and F-NET seismological networks. We finally invert the resulting datasets in order to obtain P-, SV- and SH-wave velocity models. To do so, we use a fast and efficient inversion method using ray theory. Observed structures in the three tomographic models show a very good geographical coherency. Nevertheless, some differences are observed below Songliao basin and Changbaishan volcanoes between, on the one side, P and SV models, and, on the other side, SH model. By measuring velocity ratios, we discuss anisotropy and thermal/compositional origin of these velocity anomalies.

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