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OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS

OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS. M.A. Nosov , S.V. Kolesov Faculty of Physics M.V.Lomonosov Moscow State University, Russia. OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS.

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OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS

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  1. OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS M.A. Nosov, S.V. Kolesov Faculty of Physics M.V.Lomonosov Moscow State University, Russia

  2. OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS

  3. OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS [WinITDB, 2007]:

  4. OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS

  5. INITIAL CONDITIONSor “roundabout manoeuvre” • 1. Earthquake focal mechanism: • Fault plane orientation and depth • Burgers vector 2. Slip distribution Central Kuril Islands, 15.11.2006 [http://earthquake.usgs.gov/]

  6. INITIAL CONDITIONSor “roundabout manoeuvre” • 3. Permanent vertical bottom deformations: • the Yoshimitsu Okada analytical formulae • numerical models 4. Long wave theory Central Kuril Islands, 15.11.2006

  7. OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS

  8. OPTIMALINITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS The “roundabout manoeuvre” means Initial Elevation = Vertical Bottom Deformation ??? There are a few reasons why…

  9. Dynamic bottom deformation (Mw=8) [Andrey Babeyko, PhD, GeoForschungsZentrum, Potsdam]

  10. Dynamic bottom deformation (Mw=8) permanent bottom deformation duration~10-100 s [Andrey Babeyko, PhD, GeoForschungsZentrum, Potsdam]

  11. Period of bottom oscillations

  12. Time-scales for tsunami generation L is the horizontal size of tsunami source; H is the ocean depth g is the acceleration due to gravity c is the sound velocity in water Tsunami generation is an instant process if finite duration However, if instant ocean behaves as a compressible medium

  13. Time-scales for tsunami generation L is the horizontal size of tsunami source; H is the ocean depth g is the acceleration due to gravity c is the sound velocity in water traditional assumptions (i.e. instant & incompressible) are valid Tsunami generation is an instant process if finite duration instant However, if Compressible ocean ocean behaves as a compressible medium

  14. Elastic oscillations do not propagate upslope • Elastic oscillations and gravitational waves are not coupled (in linear case) Linear = Incompressible!

  15. Initial Elevation = Vertical Bottom Deformation ???

  16. “Smoothing”: min~H exponentially decreasing function

  17. Initial Elevation = Vertical Bottom Deformation Due to “smoothing”

  18. Permanent bottom deformations vertical horizontal Central Kuril Islands, 15.11.2006

  19. Slopingbottom and 3-component bottom deformation: contribution to tsunami Normal to bottom Bottom deformation vector

  20. Slopingbottom and 3-component bottom deformation: contribution to tsunami traditionallyneglected traditionallyunder consideration

  21. Tsunami generation problem: Incompressible= Linear Linear potential theory (3D model) 1) Dynamic bottom deformation (DBD) Not instant! 2) Phase dispersion is taken into account Disadvantages: 1) Inapplicable under near-shore conditions due to nonlinearity, bottom friction etc.; 2) Numerical solution requires huge computational capability; 3) Problem with reliable DBD data.

  22. Simple way out for practice Instant generation If you can’t have the best make the best of what you have

  23. Simple way out for practice Instant generation Not only vertical but also horizontal bottom deformation is taken into account Permanent bottom deformations (all 3 components!) “Smoothing”, i.e. removing of shortwave components which are not peculiar to real tsunamis

  24. Linear shallow water theory Initial conditions: Boundary conditions: at shoreline at external boundary Initial elevation

  25. 15.11.2006 Initial Elevation=Vertical Bottom Deformation

  26. 15.11.2006 Smoothing: Initial Elevation from Laplace Problem

  27. 13.01.2007 Initial Elevation=Vertical Bottom Deformation

  28. 13.01.2007 Smoothing: Initial Elevation from Laplace Problem

  29. Comparison of runup heights calculated using traditional (pure Z) and optimal (Laplace XYZ) approach 15.11.2006 13.01.2007

  30. Conclusions: Optimal method for the specification of initial conditions in the tsunami problem is suggested and proved; The initial elevation is determined from 3D problem in the framework of linear potential theory; Both horizontal and vertical components of the bottom deformation and bathymetry in the vicinity of the source is taken into account; Short wave components which are not peculiar to gravitational waves generated by bottom motions are removed from tsunami spectrum.

  31. Thank you for your attention!

  32. 15 Nov 2006 13 Jan 2007

  33. 15 Nov 2006 13 Jan 2007

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