Tsunami Scenarios Based on Interseismic Models Along the Nankai Trough, Japan, From Seafloor and Onshore Geodesy

The recent availability of Global Positioning System‐Acoustic seafloor geodetic observations enables us to resolve the spatial distribution of the slip deficit rate near the Nankai trough, southwestern Japan. Considering a tectonic block model and the transient deformation due to the major earthquak...

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Bibliographic Details
Published in:Journal of geophysical research. Solid earth 2018-03, Vol.123 (3), p.2448-2461
Main Authors: Watanabe, Shun‐ichi, Bock, Yehuda, Melgar, Diego, Tadokoro, Keiichi
Format: Article
Language:English
Subjects:
2004 southeastern off the Kii Peninsula earthquake
Acoustic navigation
Computer simulation
Deformation
Earthquakes
Finite element method
Geodesy
Geophysics
Global positioning systems
GPS
Mathematical models
Navigation
Navigation satellites
Navigation systems
Ocean floor
Plate boundaries
Positioning systems
Rheological properties
Rheology
Satellites
seafloor GPS‐A velocity
Seismic activity
Slip
slip deficit rate inversion
Spatial distribution
Three dimensional models
tsunami generation model in the Nankai trough
Tsunamis
viscoelastic relaxation
Viscoelasticity
Wave propagation
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Summary:The recent availability of Global Positioning System‐Acoustic seafloor geodetic observations enables us to resolve the spatial distribution of the slip deficit rate near the Nankai trough, southwestern Japan. Considering a tectonic block model and the transient deformation due to the major earthquakes in this area, the slip deficit rate between the two relevant blocks can be estimated. In this study, we remove the time‐dependent postseismic deformation of the 2004 southeastern off the Kii Peninsula earthquakes (MJMA 7.1, 7.4), which had led to the underestimation of the slip deficit rate in earlier studies. We model the postearthquake viscoelastic relaxation using the 3D finite element model with bi‐viscous Burgers rheology, as well as the afterslip on the finite faults. The corrected Global Positioning System‐Acoustic and land‐based Global Navigation Satellite Systems data are aligned to the existing tectonic model and used to estimate the slip deficit rate on the plate boundary. We then calculate the coseismic displacements and tsunami wave propagation with the simple assumption that a hundred years of constant slip deficit accumulation was released instantaneously. To evaluate the influence of uncertainties in the plate interface geometry on a tsunami model for the Nankai trough, we investigated two different geometries and performed checkerboard inversion simulations. Although the two models indicate roughly similar results, the peak height of the tsunami wave and its arrival time at several points are significantly different in terms of the expected hazard. Key Points Tsunami propagation scenarios in the Nankai trough were calculated based on the geodetically determined slip deficit rate Corrections were made for postseismic relaxation and afterslip of the 2004 southeastern off the Kii Peninsula earthquakes Seafloor GPS‐Acoustic observations significantly improve tsunami scenarios when combined with onshore continuous GNSS
ISSN:2169-9313
2169-9356
DOI:10.1002/2017JB014799