Tsunami Generation Model Using Precise Seafloor Geodetic Data Along the Nankai Subduction Zone
Abstract
Dense near-fault GPS-A seafloor geodetic and on-shore GPS GEONET observations provide significantly improved resolution of the interseismic slip deficit in the Nankai trough, Japan [Yokota et al., 2016]. Here we include additional seafloor data at the Kumano basin operated by Nagoya University [Tadokoro et al., 2012] to estimate expected seafloor deformation during a large subduction zone earthquake as input to tsunami models. The slip deficit was derived from the tectonic model of Loveless and Meade [2010], aligning the geodetic data to the Nankai-block (forearc sliver); the earlier model ignored block boundaries such as the Median Tectonic Line (MTL) and may have overestimated the slip deficit rate. We modified the static model approach of Melgar and Bock [2013] using Okada's Green's functions and the CAMP standard model for the plate interface [Hashimoto et al., 2004], and divided the fault into approximately 25 x 25 km rectangular subfaults with displacements constrained to minimize Akaike's Bayesian Information Criterion. The degree of smoothing was allowed to vary according to strike and dip directions to take into account the spatial heterogeneity of the geodetic data, in particular near the trough. We then assumed that the 100-years of slip deficit was released instantaneously. We included the horizontal effect due to the geographical slope into account according to Tanioka and Satake [1996]. The forward calculation indicated that the seafloor throughout the area would lift the seawater by more than 2 m along the eastern edge of the trough, and in the southern area off Shikoku island; because of the small dip angle, neglecting the horizontal motion reduces the uplift to 1 m. A relatively large amount of strike-slip component was estimated near the trough in the eastern region from Cape Shionomisaki, contributing 1-2 m of seafloor uplift along the Suruga trough. These estimates of seafloor displacements will be useful as input to local tsunami models for disaster mitigation planning in the Nankai trough region.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMNH43A1829W
- Keywords:
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- 3225 Numerical approximations and analysis;
- MATHEMATICAL GEOPHYSICSDE: 4332 Disaster resilience;
- NATURAL HAZARDSDE: 4341 Early warning systems;
- NATURAL HAZARDSDE: 4564 Tsunamis and storm surges;
- OCEANOGRAPHY: PHYSICAL