Abstract

Long-term slow slip events (L-SSEs) have repeatedly occurred beneath the Bungo Channel in southwestern Japan with durations of several months to a couple of years, with a recurrence interval of approximately 6 years. We estimated the spatiotemporal slip distributions of the 2018–2019 Bungo Channel L-SSE by inverting processed GNSS time series data. This event was divided into two subevents, with the first on the southwest side of the Bungo Channel from 2018.3 to 2018.7 and the second beneath the Bungo Channel from 2018.8 to 2019.4. Tectonic tremors became active on the downdip side of the L-SSE occurrence region when large slow slips took place beneath the Bungo Channel. Compared with the previous Bungo Channel L-SSEs, this spatiotemporal slip pattern and amount were similar to those of the 2002–2004 L-SSE. However, the slip expanded in the northeast and southwest directions in the latter half of the second subevent. The maximum amount of slip, the maximum slip velocity, the total released seismic moment, and the moment magnitude of the 2018–2019 L-SSE were estimated to be 28 cm, 54 cm/year, 4.4 times 10^{19} Nm, and 7.0, respectively, all of which were the largest among the 1996–1998, 2002–2004, 2009–2011, and 2018–2019 L-SSEs.

Highlights

  • Long-term slow slip events (L-SSEs) have repeatedly occurred beneath the Bungo Channel in southwestern Japan with durations of several months to a couple of years, with a recurrence interval of approximately 6 years

  • The total horizontal and vertical displacements associated with the 2018–2019 L-SSE at each station during the analysis period are shown in Fig. S2a,b, respectively

  • We found the differences between them: the maximum slip amount, the released seismic moment, and the equivalent moment magnitude of the first and second subevents of the L-SSE estimated in this study were slightly larger than those of the first and second subevents of the 2002–2004 L-SSE (Table 1, Figs. 5, 6)

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Summary

Introduction

Long-term slow slip events (L-SSEs) have repeatedly occurred beneath the Bungo Channel in southwestern Japan with durations of several months to a couple of years, with a recurrence interval of approximately 6 years. Bungo Channel L-SSE by inverting processed GNSS time series data This event was divided into two subevents, with the first on the southwest side of the Bungo Channel from 2018.3 to 2018.7 and the second beneath the Bungo Channel from 2018.8 to 2019.4. Compared with the previous Bungo Channel L-SSEs, this spatiotemporal slip pattern and amount were similar to those of the 2002–2004 L-SSE. Previous studies have analysed the slip distributions of L-SSEs that occurred beneath the Bungo Channel in 1996–19982–8, 2002–20044,6–9, and 2009–20117,8. Ozawa et al.[16] analysed the spatiotemporal slip distribution of the Bungo Channel L-SSE that occurred from 2018 to 2019.

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Conclusion

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