Japan Geoscience Union Meeting 2023

Presentation information

[J] Oral

H (Human Geosciences ) » H-DS Disaster geosciences

[H-DS06] Tsunami and tsunami forecast

Mon. May 22, 2023 3:30 PM - 4:45 PM International Conference Room (IC) (International Conference Hall, Makuhari Messe)

convener:Satoko Murotani(National Museum of Nature and Science), Toshitaka Baba(Graduate School of Science and Technology, Tokushima University), Chairperson:Toshitaka Baba(Graduate School of Science and Technology, Tokushima University), Mohammad Heidarzadeh(University of Bath)

4:00 PM - 4:15 PM

[HDS06-03] Tsunami amplitude amplification due to the dynamics of the bottom deformation: case studies of real events

*Kirill Sementsov1, Yuichiro Tanioka1, Mikhail Nosov2,3, Sergey Kolesov2,3 (1.Hokkaido University, Faculty of Science, Institute of Seismology and Volcanology, 2.M.V.Lomonosov Moscow State University, Chair of Physics of Sea and Inland Water, Faculty of Physics, Moscow, Russia, 3.Institute of Marine Geology and Geophysics, Far Eastern Branch of Russian Academy of Sciences, Yuzhno-Sakhalinsk, Russia)

Keywords:tsunami generation, tsunami simulation, ocean bottom kinematics

Traditionally in tsunami simulation the initial water surface elevation in the tsunami source is used as an initial condition. For the calculation of this initial elevation the three component ocean bottom displacement field is used while the effect of bottom topography [1] and the smoothing effect of water layer [2] are taken into account. Theoretical analysis shows that under certain conditions the significant amplification of the tsunami amplitude due to the bottom deformation dynamics could be observed. In particuar, the rupture propagation velocity should be comparable to the long waves velocity and the uplifted area should be large enough [3-6]. Not all the real tsunami sources meet the above mentioned conditions, but for some sources these conditions occured. We present the detailed analysis of such events.
Finite Fault products provided by the USGS web site allows us to create two different types of the seafloor displacement fields: the final displacement field and the time-dependent displacement field. We used these two types of the bottom displacement field as an input data for the comparative tsunami simulation, considering passive and active tsunami generation scenarios, respectively [7]. Active generation scenario means that for the tsunami simulation we use the bottom movement as a time-dependent kinematic boundary condition. Passive generation scenario means that we use an initial elevation of the water surface in the tsunami source as an initial condition for simulation. Tsunami simulations were performed with the use of the Combined Potential Tsunami Model (CPTM) [8, 9]. CPTM model solves 3D wave equations for the compressible fluid and allows to dynamically input the bottom movement information on each time step of the simulation.
Comparative numerical simulation showed, that the tsunami amplitude amplification takes place during the strong events (for example, 2011/03/11 catastrophic Mw 9.1 Tohoku event or 2006/11/15 Mw 8.3 Kuril Islands event), and also during the tsunami earthquakes (for example, 1992/09/02 Mw 7.7 Nicaragua event). The features of the directivity diagrams of the tsunami energy radiation for different cases will be discussed.

References
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9. Sementsov K. A., Nosov M. A., Kolesov S. V., Karpov V. A., Matsumoto H., Kaneda Y. (2019). Free gravity waves in the ocean excited by seismic surface waves: Observations and numerical simulations //Journal of Geophysical Research: Oceans. 124. – No.. 11. – P. 8468-8484.