Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

S (Solid Earth Sciences ) » S-SS Seismology

[S-SS06] Nankai Trough Seismogenic Zone Experiment: Logging and sampling the seismogenic megathrust

Tue. May 28, 2019 1:45 PM - 3:15 PM Convention Hall B (2F)

convener:Kyuichi Kanagawa(Graduate School of Science, Chiba University), Demian M Saffer(Pennsylvania State University), Masataka Kinoshita(Earthquake Research Institute, University of Tokyo), Chairperson:Kyuichi Kanagawa(Graduate School of Science, Chiba University), Demian Saffer(Department of Geosciences, Pennsylvania State University), Masataka Kinoshita(Earthquake Research Institute, the University of Tokyo)

1:45 PM - 2:00 PM

[SSS06-01] Geoscientific information about plate boundary along the Nankai Trough provided by the GNSS-A

★Invited Papers

*Yusuke Yokota1, Tadashi Ishikawa2 (1.Institute of Industrial Science, The University of Tokyo, 2.Hydrographic and Oceanographic department, Japan Coast Guard)

Keywords:GNSS-A, Nankai Trough, SSE, plate boundary, coupling condition

In the last decade, many geophysical implications were provided by the GNSS-A seafloor geodetic network. Along the Japan Trench, coseismic and postseismic deformations following the 2011 Tohoku-oki earthquake were detected [Sato et al., 2011, Science; Watanabe et al., 2014, GRL; Tomita et al., 2017, Sci. Adv.]. Coseismic monitoring result was applied for many seismological research [e.g., Ozawa et al., 2012, JGR] and geological research and monitoring plan. Postseismic viscoelastic behavior and afterslip event [Sun et al., 2016, Nature; Iinuma et al., 2016, Nature Comm.] could not be identified without our monitoring results.

After 2015, more important geoscientific suggestions were obtained from monitoring in the Nankai Trough. Yokota et al. [2016, Nature] showed undersea interseismic coupling condition. This observation result has been broadly applied to various geophysical studies while being modified [e.g., Nishimura et al., 2018, Gesphere; Noda et al., 2018, JGR] and constrains earthquake prediction research including numerical simulation and submarine drilling research.

In addition, recently, we improved the GNSS-A technology and upgraded observation frequency and precision [Yokota et al., 2017, Rep. Hydro. Ocean. Res; Yokota et al., 2018, MGR]. With the present observation ability, yearly time change of the amount of undersea crustal deformation was newly unclosed. This new version data suggests that there were longer-term sequences of slow slip events (SSEs) around strong coupling regions [Yokota and Ishikawa, this JpGU meeting].

These results provide several suggestions about property and condition on the plate boundary. The simple and biggest question is what is the reason for separating strong coupling and SSE conditions. Since the difference between the generation patterns of SSE and other slow earthquakes is also considered to be due to physical properties, some dominant factor can be assumed. Differences and similarities between deep and shallow SSEs are also important. What physical properties control the behaviors of deep and shallow SSEs?

For answering these questions, additional experiments and observations from many different viewpoints will be necessary. At the same time, continuous GNSS-A monitoring and upgrading its density and accuracy are required for understanding shallow coupling conditions and SSEs.