5:15 PM - 6:30 PM
[SSS05-P03] Long-term SSE along the Nankai trough detected by Geonet
Keywords:long-term SSE, Nankai trough, GNSS
GNSS network has revealed transitional crustal movements in the Kyushu, Shikoku, Kii Channel, and Shima Peninsula areas since 2018. The interplate slip in the Nankai Trough area was estimated from the observed transient. As a result, from June 2018 to August 2019, SSE has occurred in the northern part of Hyuga Nada and Bungo Channel, and from early 2019 to late 2020, SSE has occurred in central Shikoku. It was estimated that SSE occurred in Kii Channel from around April 2019 to late 2020, and SSE occurred in the Shima Peninsula from around early 2019 to around April 2020. Northern and southern Hyuga-nada SSE occurred from mid 2020.
Introduction
In Bungo Channel, long-term SSE has repeatedly occurred in a cycle of 5 to 6 years. In central Shikoku, long-term SSE is estimated in 1977-1980, 1998, 2004, 2010, 2012, and 2015. The long-term SSE of Kii Channel occurred in 1996, 2000 and 2016. The Shima Peninsula SSE occurred during 2017-2018. Transitional crustal movements have occurred in northern Kyushu from around June 2018, and from around October 2018, in the Bungo Channel. Transient have been observed around Kii Channel since April 2019, and in the Shima Peninsula area since early 2019. In this study, we estimated the spatiotemporal variation of interplate slip in the Shikoku, Kyushu, Kii Channel, and Shima Peninsula from the data of crustal deformation detected by GNSS.
Analytical Procedure
From the position time series, the annual and semi-annual components for 2013-2019 were estimated and removed from the original position time series. The 2017-2018 trend is subtracted from the analysis for the Kyushu, Shikoku and the Kii channel areas, and the primary trend from March 2016 to March 2017 is subtracted from the Shima Peninsula analysis. Time-dependent inversion analysis was performed using the east-west, north-south, and top-bottom coordinate time-series data at 250 observation points. The shape of the Philippine Sea plate compiled by Hirose et al. (2008) is represented by triangular elements and used for analysis. The grid interval is about 20-40km. The slip direction on the plate boundary was constrained to be the plate converging direction.
Results and discussion
From around June 2018 to around August 2019, SSE occurred in Bungo Channel and in northern Hinata Nada. SSE occurred in central Shikoku from early 2019 to late 2020. The SSE of Kii-channel occurred around April 2019 and ended in late 2020. The Shima Peninsula SSE occurred from early 2019 and ended around April 2020. It was estimated that Bungo channel SSE was Mw 6.9, central Shikoku SSE was Mw 6.1, Kii channel SSE was Mw 6.1, and Shima Peninsula SSE was Mw 6.2. The Bungo channel SSE is roughly in harmony with the 5-6 year cycle. The repeating intervals of central Shikoku SSE do not seem to be periodic. The Kii Channel SSE does not appear to have a periodic interval. It is not clear whether Shima peninsula SSE is a series of SSEs or separate SSEs, which started from 2017. Northern Hyuga-nada SSE started from 2018 and subsided in early 2020 and started from the middle of 2020, whose rupture history seems to be different from those of the past events.
Introduction
In Bungo Channel, long-term SSE has repeatedly occurred in a cycle of 5 to 6 years. In central Shikoku, long-term SSE is estimated in 1977-1980, 1998, 2004, 2010, 2012, and 2015. The long-term SSE of Kii Channel occurred in 1996, 2000 and 2016. The Shima Peninsula SSE occurred during 2017-2018. Transitional crustal movements have occurred in northern Kyushu from around June 2018, and from around October 2018, in the Bungo Channel. Transient have been observed around Kii Channel since April 2019, and in the Shima Peninsula area since early 2019. In this study, we estimated the spatiotemporal variation of interplate slip in the Shikoku, Kyushu, Kii Channel, and Shima Peninsula from the data of crustal deformation detected by GNSS.
Analytical Procedure
From the position time series, the annual and semi-annual components for 2013-2019 were estimated and removed from the original position time series. The 2017-2018 trend is subtracted from the analysis for the Kyushu, Shikoku and the Kii channel areas, and the primary trend from March 2016 to March 2017 is subtracted from the Shima Peninsula analysis. Time-dependent inversion analysis was performed using the east-west, north-south, and top-bottom coordinate time-series data at 250 observation points. The shape of the Philippine Sea plate compiled by Hirose et al. (2008) is represented by triangular elements and used for analysis. The grid interval is about 20-40km. The slip direction on the plate boundary was constrained to be the plate converging direction.
Results and discussion
From around June 2018 to around August 2019, SSE occurred in Bungo Channel and in northern Hinata Nada. SSE occurred in central Shikoku from early 2019 to late 2020. The SSE of Kii-channel occurred around April 2019 and ended in late 2020. The Shima Peninsula SSE occurred from early 2019 and ended around April 2020. It was estimated that Bungo channel SSE was Mw 6.9, central Shikoku SSE was Mw 6.1, Kii channel SSE was Mw 6.1, and Shima Peninsula SSE was Mw 6.2. The Bungo channel SSE is roughly in harmony with the 5-6 year cycle. The repeating intervals of central Shikoku SSE do not seem to be periodic. The Kii Channel SSE does not appear to have a periodic interval. It is not clear whether Shima peninsula SSE is a series of SSEs or separate SSEs, which started from 2017. Northern Hyuga-nada SSE started from 2018 and subsided in early 2020 and started from the middle of 2020, whose rupture history seems to be different from those of the past events.